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Subject: Chaum's Dining Cryptographers [LONG] (was: Digital Money again)
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Someone suggested that Allan Bailey seek this paper on soda.berkeley.edu. It is
not there, but it was posted to the list last December. Here it is again.

Date: 11 Dec 1992 14:58:38 -0800
From: [e-mail]
Subject: Chaum's "The Dining Cryptographers Problem" (VERY LONG)
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The following article is brought to you by the Information Liberation
Front (ILF), a group dedicated to the timely distribution of important
information.

The ILF encourages you to use this article for educational purposes
only and to seek out the original article. Minor spelling errors and
slight alterations of formulas may have gotten past the OCR process.

We apologize for the length, but feel this is one of the key articles
in this area.


J. Cryptology (1988) 1:65-75

The Dining Cryptographers Problem:

Unconditional Sender and Recipient Untraceability

David Chaum
Centre for Mathematics and Computer Science, Kruislan 413, 1098 SJ
Amsterdam, The Netherlands

Abstract.  Keeping confidential who sends which messages, in a
world where any physical transmission can be traced to its
origin, seems impossible. The solution presented here is
unconditionally or cryptographically secure, depending on whether
it is based on one-time-use keys or on public keys, respectively.
It can be adapted to address efficiently a wide variety of
practical considerations.

Key words.  Untraceability, Unconditional Security, Pseudonymity.

Introduction

Three cryptographers are sitting down to dinner at their favorite
three-star restaurant. Their waiter informs them that arrangements
have been made with the maitre d'hotel for the bill to be paid
anonymously. One of the cryptographers might be paying for the dinner,
or it might have been NSA (U.S. National Security Agency). The three
cryptographers respect each other's right to make an anonymous
payment, but they wonder if NSA is paying. They resolve their
uncertainty fairly by carrying out the following protocol:

Each cryptographer flips an unbiased coin behind his menu, between
him and the cryptographer on his right, so that only the two of them can
see the outcome. Each cryptographer then states aloud whether the two
coins he can see--the one he flipped and the one his left-hand neighbor
flipped--fell on the same side or on different sides. If one of the
cryptographers is the payer, he states the opposite of what he sees. An
odd number of differences uttered at the table indicates that a
cryptographer is paying; an even number indicates that NSA is paying
(assuming that the dinner was paid for only once). Yet if a
cryptographer is paying, neither of the other two learns anything from
the utterances about which cryptographer it is.

To see why the protocol is unconditionally secure if carried out
faithfully, consider the dilemma of a cryptographer who is not the
payer and wishes to find out which cryptographer is. (If NSA pays, there
is no anonymity problem.) There are two cases. In case (1) the two
coins he sees are the same, one of the other cryptographers said
"different," and the other one said "same." If the hidden outcome was
the same as the two outcomes he sees, the cryptographer who said
"different" is the payer; if the outcome was different, the one who said
"same" is the payer. But since the hidden coin is fair, both possibilities
are equally likely. In case (2) the coins he sees are different; if both
other cryptographers said "different," then the payer is closest to the
coin that is the same as the hidden coin; if both said "same," then the
payer is closest to the coin that differs from the hidden coin. Thus, in
each subcase, a nonpaying cryptographer learns nothing about which of
the other two is paying.

The cryptographers become intrigued with the ability to make
messages public untraceably. They devise a way to do this at the table
for a statement of arbitrary length: the basic protocol is repeated over
and over; when one cryptographer wishes to make a message public, he
merely begins inverting his statements in those rounds corresponding
to 1 's in a binary coded version of his message. If he notices that his
message would collide with some other message, he may for example
wait a number of rounds chosen at random from a suitable distribution
before trying to transmit again.

1. Generalizing the Approach

During dinner, the cryptographers also consider how any number of
participants greater than one can carry out a version of the protocol.
(With two participants, only nonparticipant listeners are unable to
distinguish between the two potential senders.) Each participant has a
secret key bit in common with, say, every other participant. Each
participant outputs the sum, modulo two, of all the key bits he shares,
and if he wishes to transmit, he inverts his output. If no participant
transmits, the modulo two sum of the outputs must be zero, since every
key bit enters exactly twice; if one participant transmits, the sum
must be one. (In fact, any even number of transmitting participants
yields zero, and any odd number yields one.) For j rounds, each
participant could have a j-bit key in common with every other
participant, and the ith bit of each such key would be used only in the
ith round. Detected collision of messages leads to attempted
retransmission as described above; undetected collision results only
from an odd number of synchronized identical message segments.
(Generalization to fields other than GF(2) is possible, but seems to
offer little practical advantage.)

Other generalizations are also considered during dinner. The
underlying assumptions are first made explicit, including modeling
key-sharing arrangements as graphs. Next, the model is illustrated
with some simple examples. The potential for cooperations of
participants to violate the security of others is then looked at. Finally,
a proof of security based on systems of linear equations is given.

1.1. Model

Each participant is assumed to have two kinds of secret: (a) the keys
shared with other participants for each round; and (b) the inversion
used in each round (i.e., a 1 if the participant inverts in that round and a
0 if not). Some or all of a participant's secrets may be given to other
participants in various forms of collusion, discussion of which is
postponed until Section 1.3. (For simplicity in exposition, the
possibility of secrets being stolen is ignored throughout.)

The remaining information about the system may be described as: (a)
who shares keys with whom; and (b) what each participant outputs
during each round (the modulo two sum of that participant's keys and
inversion). This information need not be secret to ensure
untraceability. If it is publicly known and agreed, it allows various
extensions discussed in Sections 2.5 and 2.6. The sum of all the
outputs will, of course, usually become known to all participants.

In the terminology of graphs, each participant corresponds to a
vertex and each key corresponds to an edge. An edge is incident on the
vertices corresponding to the pair of participants that shares the
corresponding key. From here on, the graph and dinner-table
terminologies will be used interchangeably. Also, without loss of
generality, it will be assumed that the graph is connected (i.e., that a
path exists between every pair of vertices), since each connected
component (i.e., each maximal connected subgraph) could be considered
a separate untraceable-sender system.

An anonymity set seen by a set of keys is the set of vertices in a
connected component of the graph formed from the original graph by
removing the edges concerned. Thus a set of keys sees one anonymity
set for each connected partition induced by removing the keys. The main
theorem of Section 1.4 is essentially that those having only the public
information and a set of keys seeing some anonymity set can learn
nothing about the members of that anonymity set except the overall
parity of their inversions. Thus, for example, any two participants
connected by at least one chain of keys unknown to an observer are both
in the same anonymity set seen by the observer's keys, and the observer
gains nothing that would help distinguish between their messages.

1.2. Some Examples

A few simple consequences of the above model may be illustrative. The
anonymity set seen by the empty set (i.e., by a nonparticipant observer)
is the set of all vertices, since the graph is assumed connected and
remains so after zero edges are removed. Also, the anonymity sets seen
by the full set of edges are all singleton sets, since each vertex's
inversion is just the sum of its output and the corresponding key bits.

If all other participants cooperate fully against one, of course no
protocol can keep that singleton's messages untraceable, since
untraceability exists only among a set of possible actors, and if the set
has only one member, its messages are traceable. For similar reasons,
if a participant believes that some subset of other participants will
fully cooperate against him, there is no need for him to have keys in
common with them.

A biconnected graph (i.e., a graph with at least two vertex-disjoint
paths between every pair of vertices) has no cut-vertices (i.e., a single
vertex whose removal partitions the graph into disjoint subgraphs). In
such a graph, the set of edges incident on a vertex v sees (apart from v)
one anonymity set containing all other vertices, since there is a path
not containing v between every pair of vertices, and thus they form a
connected subgraph excluding v; each participant acting alone learns
nothing about the contribution of other participants.

1.3. Collusion of Participants

Some participants may cooperate by pooling their keys in efforts to
trace the messages of others; such cooperation will be called collusion.
For simplicity, the possibilities for multiple collusions or for pooling
of information other than full edges will be ignored. Colluders who lie
to each other are only touched on briefly, in Section 2.6.

Consider collusion in a complete graph. A vertex is only seen as a
singleton anonymity set by the collection of all edges incident on it; all
other participants must supply the key they share with a participant in
order to determine that participant's inversions. But since a collusion
of all but one participant can always trace that participant merely by
pooling its members' inversions as already mentioned, it gains nothing
more by pooling its keys. The nonsingleton anonymity set seen by all
edges incident on a colluding set of vertices in a complete graph is the
set of all other vertices; again, a collusion yields nothing more from
pooling all its keys than from pooling all its inversions.

Now consider noncomplete graphs. A full collusion is a subset of
participants pooling all of their keys. The pooled keys see each colluder
as a singleton anonymity set; the colluders completely sacrifice the
untraceability of their own messages. If a full collusion includes a cut-
set of vertices (i.e., one whose removal partitions the graph), the
collusion becomes nontrivial because it can learn something about the
origin of messages originating outside the collusion; the noncolluding
vertices are partitioned into disjoint subgraphs, which are the
anonymity sets seen by the pooled keys.

Members of a partial collusion pool some but not all of their keys.
Unlike the members of a full collusion, each member of a partial
collusion in general has a different set of keys. For it to be nontrivial,
a partial collusion's pooled keys must include the bridges or separating
edges of a segregation or splitting of the graph (i.e., those edges whose
removal would partition the graph). Settings are easily constructed in
which the pooled keys see anonymity sets that partition the graph and
yet leave each colluder in a nonsingleton partition seen by any other
participant. Thus, colluders can join a collusion without having to make
themselves completely traceable to the collusion's other members.

1.4. Proof of Security

Consider, without loss of generality, a single round in which say some
full collusion knows some set of keys. Remove the edges known to the
collusion from the key-sharing graph and consider any particular
connected component C of the remaining graph. The vertices of C thus
form an anonymity set seen by the pooled keys.

Informally, what remains to be shown is that the only thing the
collusion learns about the members of C is the parity sum of their
inversions. This is intuitively apparent, since the inversions of the
members of C are each in effect hidden from the collusion by one or
more unknown key bits, and only the parity of the sum of these key bits
is known (to be zero). Thus the inversions are hidden by a one-time pad,
and only their parity is revealed, because only the parity of the pad is
known.

The setting is formalized as follows: the connected component C is
comprised of rn vertices and n edges. The incidence matrix M of C is
defined as usual, with the vertices labeling the rows and the edges
labeling the columns. Let K, I, and A be stochastic variables defined on
GF(2)^n, GF(2)^m, and GF(2)^m, respectively, such that
K is uniformly distributed over GF(2)^n, K and I are mutually
independent, and A = (MK) cross I. In terms of the protocol, K comprises
the keys corresponding to the edges, I consists of the inversions
corresponding to the vertices, and A is formed by the outputs of the
vertices. Notice that the parity of A (i.e., the modulo two sum of its
components) is always equal to the parity of I, since the columns of M
each have zero parity. The desired result is essentially that A reveals
no more information about I than the parity of 1. More formally:

Theorem.  Let a be in GF(2)^n. For each i in GF(2)^n, which is assumed by
I with nonzero probability and which has the same parity as a, the
conditional probability that A = a given that I = i is 2^(1 - m). Hence,
the conditional probability that I = i given that A = a is the a priori
probability that I = i.

Proof.  Let i be an element of GF(2)^n have the same parity as a.
Consider the system of linear equations (MK) cross i = a, in k an
element of GF(2)^n. Since the columns of M each have even parity, as
mentioned above, its rows are linearly dependent over GF(2)^m. But as a
consequence of the connectedness of the graph, every proper subset of
rows of M is linearly independent. Thus, the rank of M is m - 1, and so
each vector with zero parity can be written as a linear combination of
the columns of M. This implies that the system is solvable because i
cross a has even parity. Since the set of n column vectors of M has rank
m - 1, the system has exactly 2^(n - m + 1) solutions.

Together with the fact that K and I are mutually independent and
that K is uniformly distributed, the theorem follows easily.

2. Some Practical Considerations

After dinner, while discussing how they can continue to make
untraceable statements from this respective homes, the cryptographers
take up a variety of other topics. In particular, they consider different
ways to establish the needed keys; debate adapting the approach to
various kinds of communication networks; examine the traditional
problems of secrecy and authentication in the context of a system that
can provide essentially optimal untraceability; address denial of
service caused by malicious and devious participants; and propose
means to discourage socially undesirable messages from being sent.

2.1. Establishing Keys

One way to provide the keys needed for longer messages is for one
member of each pair to toss many coins in advance. Two identical
copies of the resulting bits are made, say each on a separate optical
disk. Supplying one such disk (which today can hold on the order of
10^10 bits) to a partner provides enough key bits to allow people to
type messages at full speed for years. If participants are not
transmitting all the time, the keys can be made to last even longer by
using a substantially slower rate when no message is being sent; the
full rate would be invoked automatically only when a 1 bit indicated
the beginning of a message. (This can also reduce the bandwidth
requirements discussed in Section 2.2.)

Another possibility is for a pair to establish a short key and use a
cryptographic pseudorandom-sequence generator to expand it as needed.
Of course this system might be broken if the generator were broken.
Cryptanalysis may be made more difficult, however, by lack of access
to the output of individual generators. Even when the cryptographers do
not exchange keys at dinner, they can safely do so later using a public-
key distribution system (first proposed by [4] and [3]).

2.2 Underlying Communication Techniques

A variety of underlying communication networks can be used, and their
topology need not be related to that of the key-sharing graph.

Communication systems based on simple cycles, called rings, are
common in local area networks. In a typical ring, each node receives
each bit and passes it round-robin to the next node. This technology is
readily adapted to the present protocols. Consider a single-bit message
like the "I paid" message originally sent at the dinner table. Each
participant exclusive-or's the bit he receives with his own output
before forwarding it to the next participant. When the bit has traveled
full circle, it is the exclusive-or sum of all the participants' outputs,
which is the desired result of the protocol. To provide these messages
to all participants, each bit is sent around a second time by the
participant at the end of the loop.

Such an adapted ring requires, on average, a fourfold increase in
bandwidth over the obvious traceable protocols in which messages
travel only halfway around on average before being taken off the ring by
their recipients. Rings differ from the dinner table in that several bit-
transmission delays may be required before all the outputs of a
particular round are known to all participants; collisions are detected
only after such delays.

Efficient use of many other practical communication techniques
requires participants to group output bits into blocks. For example, in
high-capacity broadcast systems, such as those based on coaxial cable,
surface radio, or satellites, more efficient use of channel capacity is
obtained by grouping a participant's contribution into a block about the
size of a single message (see, e.g., [5]). Use of such communication
techniques could require an increase in bandwidth on the order of the
number of participants.

In a network with one message per block, the well-known contention
protocols can be used: time is divided evenly into frames; a participant
transmits a block during one frame; if the block was garbled by
collision (presumably with another transmitted block), the participant
waits a number of frames chosen at random from some distribution
before attempting to retransmit; the participants' waiting intervals
may be adjusted on the basis of the collision rate and possibly of other
heuristics [5].

In a network with many messages per block, a first block may be
used by various anonymous senders to request a "slot reservation" in a
second block. A simple scheme would be for each anonymous sender to
invert one randomly selected bit in the first block for each slot they
wish to reserve in the second block. After the result of the first block
becomes known, the participant who caused the ith 1 bit in the first
block sends in the ith slot of the second block.

2.3. Example Key-Sharing Graphs

In large systems it may be desirable to use fewer than the m(m - 1)/2
keys required by a complete graph. If the graph is merely a cycle, then
individuals acting alone learn nothing, but any two colluders can
partition the graph, perhaps fully compromising a participant
immediately between them. Such a topology might nevertheless be
adequate in an application in which nearby participants are not likely
to collude against one another.

A different topology assumes the existence of a subset of
participants who each participant believes are sufficiently unlikely to
collude, such as participants with conflicting interests. This subset
constitutes a fully connected subgraph, and the other participants each
share a key with every member of it. Every participant is then
untraceable among all the others, unless all members of the completely
connected subset cooperate. (Such a situation is mentioned again in
Section 3.)

If many people wish to participate in an untraceable communication
system, hierarchical arrangements may offer further economy of keys.
Consider an example in which a representative from each local fully
connected subgraph is also a member of the fully connected central
subgraph. The nonrepresentative members of a local subgraph provide
the sum of their outputs to their representative. Representatives would
then add their own contributions before providing the sum to the
central subgraph. Only a local subgraph's representative, or a collusion
of representatives from all other local subgraphs, can recognize
messages as coming from the local subgraph. A collusion comprising
the representative and all but one nonrepresentative member of a local
subgraph is needed for messages to be recognized as coming from the
remaining member.

2.4. Secrecy and Authentication

What about the usual cryptologic problems of secrecy and
authentication?

A cryptographer can ensure the secrecy of an anonymous message by
encrypting the message with the intended recipient's public key. (The
message should include a hundred or so random bits to foil attempts to
confirm a guess at its content [1].) The sender can even keep the
identity of the intended recipient secret by leaving it to each recipient
to try to decrypt every message. Alternatively, a prearranged prefix
could be attached to each message so that the recipient need only
decrypt messages with recognized prefixes. To keep even the
multiplicity of a prefix's use from being revealed, a different prefix
might be used each time. New prefixes could be agreed in advance,
generated cryptographically as needed, or supplied in earlier messages.

Authentication is also quite useful in systems without identification.
Even though the messages are untraceable, they might still bear
digital signatures corresponding to public-key "digital pseudonyms"
[1]; only the untraceable owner of such a pseudonym would be able to
sign subsequent messages with it. Secure payment protocols have
elsewhere been proposed in which the payer and/or the payee might be
untraceable [2]. Other protocols have been proposed that allow
individuals known only by pseudonyms to transfer securely information
about themselves between organizations [2]. All these systems require
solutions to the sender untraceability problem, such as the solution
presented here, if they are to protect the unlinkability of pseudonyms
used to conduct transactions from home.

2.5. Disruption

Another question is how to stop participants who, accidentally or even
intentionally, disrupt the system by preventing others from sending
messages. In a sense, this problem has no solution, since any
participant can send messages continuously, thereby clogging the
channel. But nondisupters can ultimately stop disruption in a system
meeting the following requirements: (1) the key-sharing graph is
publicly agreed on; (2) each participant's outputs are publicly agreed on
in such a way that participants cannot change their output for a round
on the basis of other participants' outputs for that round; and (3) some
rounds contain inversions that would not compromise the
untraceability of any nondisrupter.

The first requirement has already been mentioned in Section 1.1,
where it was said that this information need not be secret; now it is
required that this information actually be made known to all
participants and that the participants agree on it.

The second requirement is in part that disrupters be unable (at least
with some significant probability) to change their output after hearing
other participants' outputs. Some actual channels would automatically
ensure this, such as broadcast systems in which all broadcasts are
made simultaneously on different frequencies. The remainder of the
second requirement, that the outputs be publicly agreed on, might also
be met by broadcasting. Having only channels that do not provide it
automatically, an effective way to meet the full second requirement
would be for participants to "commit" to their outputs before making
them. One way to do this is for participants to make public and agree on
some (possibly compressing and hierarchical, see Section 2.6) one-way
function of their outputs, before the outputs are made public.

The third requirement is that at least some rounds can be contested
(i.e., that all inversions can be made public) without compromising the
untraceability of non-disrupting senders. The feasibility of this will be
demonstrated here by a simple example protocol based on the slot
reservation technique already described in Section 2.2.

Suppose that each participant is always to make a single reservation
in each reserving block, whether or not he actually intends to send a
message. (Notice that, because of the "birthday paradox," the number of
bits per reserving block must be quadratic in the number of
participants.) A disrupted reserving block would then with very high
probability have Hamming weight unequal to the number of participants.
All bits of such a disrupted reserving block could be contested without
loss of untraceability for nondisrupters.

The reserved blocks can also be made to have such safely contestable
bits if participants send trap messages. To lay a trap, a participant
first chooses the index of a bit in some reserving block, a random
message, and a secret key. Then the trapper makes public an
encryption, using the secret key, of both the bit index and the random
message. Later, the trapper reserves by inverting in the round
corresponding to the bit index, and sends the random message in the
resulting reserved slot. If a disrupter is unlucky enough to have
damaged a trap message, then release of the secret key by the trapper
would cause at least one bit of the reserved slot to be contested.

With the three requirements satisfied, it remains to be shown how
if enough disrupted rounds are contested, the disrupters will be
excluded from the network.

Consider first the case of a single participant's mail computer
disrupting the network. If it tells the truth about contested key bits it
shares (or lies about an even number of bits), the disrupter implicates
itself, because its contribution to the sum is unequal to the sum of
these bits (apart from any allowed inversion). If, on the other hand, the
single disrupter lies about some odd number of shared bits, the values
it claims will differ from those claimed for the same shared bits by
the other participants sharing them. The disrupter thereby casts
suspicion on all participants, including itself, that share the disputed
bits. (It may be difficult for a disrupter to cast substantial suspicion
on a large set of participants, since all the disputed bits will be in
common with the disrupter.) Notice, however, that participants who
have been falsely accused will know that they have been--and by
whom--and should at least refuse to share bits with the disrupter in
the future.

Even with colluding multiple disrupters, at least one inversion must
be revealed as illegitimate or at least one key bit disputed, since the
parity of the outputs does not correspond to the number of legitimate
inversions. The result of such a contested round will be the removal of
at least one edge or at least one vertex from the agreed graph. Thus, if
every disruptive action has a nonzero probability of being contested,
only a bounded amount of disruption is possible before the disrupters
share no keys with anyone in the network, or before they are revealed,
and are in either case excluded from the network.

The extension presented next can demonstrate the true value of
disputed bits, and hence allows direct incrimination of disrupters.

2.6. Tracing by Consent

Antisocial use of a network can be deterred if the cooperation of most
participants makes it possible, albeit expensive, to trace any message.
If, for example, a threatening message is sent, a court might order all
participants to reveal their shared key bits for a round of the message.
The sender of the offending message might try to spread the blame,
however, by lying about some odd number of shared bits. Digital
signatures can be used to stop such blame-spreading altogether. In
principle, each party sharing a key could insist on a signature, made by
the other party sharing, for the value. of each shared bit.

Such signatures would allow for contested rounds to be fully resolved,
for accused senders to exonerate themselves, and even for colluders to
convince each other that they are pooling true keys.  Unfortunately,
cooperating participants able to trace a message to its sender could
convince others of the message's origin by revealing the sender's own
signatures. A variation can prevent a participant's signatures from
being used against him in this way: instead of each member of a pair
of participants signing the same shared key bit, each signs a separate
bit, such that the sum of the signed bits is the actual shared key
bit. Signatures on such "split" key bits would still be useful in
resolving contested rounds, since if one contester of a bit shows a
signature made by the second contester, then the second would have to
reveal the corresponding signature made by the first or be thought to
be a disrupter.

In many applications it may be impractical to obtain a separate
signature on every key bit or split key bit. The overhead involved could
be greatly reduced, however, by digitally signing cryptographic
compressions of large numbers of key bits. This might of course require
that a whole block of key bits be exposed in showing a signature, but
such blocks could be padded with cryptographically generated
pseudorandom (or truly random) bits, to allow the exposure of fewer
bits per signature. The number of bits and amount of time required to
verify a signature for a single bit can be reduced further by using a
rooted tree in which each node is the one-way compression function of
all its direct descendants; only a digital signature of each participant's
root need be agreed on before use of the keys comprising the leaves.

3. Relation to Previous Work

There is another multiparty-secure sender-untraceability protocol in
the literature [1]. To facilitate comparison, it will be called a mix-net
here, while the protocol of the present work is called a dc-net. The
mix-net approach relies on the security of a true public-key system
(and possibly also of a conventional cryptosystem), and is thus at best
computationally secure; the dc-net approach can use unconditional
secrecy channels to provide an unconditionally secure untraceable-
sender system, or can use public-key distribution to provide a
computationally secure system (as described in Section 2.1).

Under some trust assumptions and channel limitations, however,
mix-nets can operate where dc-nets cannot. Suppose that a subset of
participants is trusted by every other participant not to collude and
that the bandwidth of at least some participants' channels to the
trusted subset is incapable of handling the total message traffic. Then
mix-nets may operate quite satisfactorily, but dc-nets will be unable
to protect fully each participant's untraceability. Mix-nets can also
provide recipient untraceability in this communication environment,
even though there is insufficient bandwidth for use of the broadcast
approach (mentioned in Section 2.4).

If optimal protection against collusion is to be provided and the
crypto-security of mix-nets is acceptable, a choice between mix-nets
and dc-nets may depend on the nature of the traffic. With a mail-like
system that requires only periodic deliveries, and where the average
number of messages per interval is relatively large, mix-nets may be
suitable. When messages must be delivered continually and there is no
time for batching large numbers of them, dc-nets appear preferable.

4. Conclusion

This solution to the dining cryptographers problem demonstrates that
unconditional secrecy channels can be used to construct an
unconditional sender-untraceability channel. It also shows that a
public-key distribution system can be used to construct a
computationally secure sender-untraceability channel. The approach
appears able to satisfy a wide range of practical concerns.

Acknowledgments

I am pleased to thank Jurjen Bos, Gilles Brassard, Jan-Hendrik Evertse,
and the untraceable referees for all their help in revising this article.
It is also a pleasure to thank, as in the original version that was
distributed at Crypto 84, Whitfield Diffie, Ron Rivest, and Gus Simmons
for some stimulating dinner-table conversations.

References

[1] Chaum, D., Untraceable Electronic Mail, Return Addresses, and
Digital Pseudonyms, Communications of the  ACM, vol. 24, no. 2,
February 1981, pp. 84-88.
[2] Chaum, D., Security Without Identification: Transaction Systems
to Make Big Brother Obsolete, Communications of the ACM, vol. 28,
no. 10, October 1985, pp. 1030-1044.
[3] Diffie, W., and Hellman, M.E., New Directions in Cryptography, IEEE
Transactions on Information Theory, vol. 22, no. 6, November 1976,
pp. 644-654.
[4] Merkle, R.C., Secure Communication over Insecure Channels,
Communications of the ACM, vol. 21, no. 4, 1978, pp. 294-299.
[5] Tanenbaum, A.S., Computer Networks, Prentice Hall, Englewood
Cliffs, New Jersey, 1981.


[End of Transmission]


Date: 03 Dec 1992 08:29:12 -0800 (PST)
From: [e-mail] (Timothy C. May)
Subject: RE: faq & glossary
In-reply-to: <[e-mail]>; from "[e-mail]" at
 Dec 2, 92 8:16 pm
To: [e-mail]
Message-id: <[e-mail]>
Content-transfer-encoding: 7BIT
X-Mailer: ELM [version 2.3 PL11]



CRYPTO GLOSSARY

Compiled by Tim May ([e-mail]) and Eric Hughes
([e-mail]), circa September 1992.

Major Branches of Cryptology (as we see it)

- (these sections will introduce the terms in context,
though complete definitions will not be given)

*** Encryption
- privacy of messages
- using ciphers and codes to protect the secrecy of
messages
- DES is the most common symmetric cipher (same key for
encryption and decryption)
- RSA is the most common asymmetric cipher (different
keys for encryption and decryption)

*** Signatures and Authentication
- proving who you are
- proving you signed a document (and not someone else)

*** Untraceable Mail
- untraceable sending and receiving of mail and messages
- focus: defeating eavesdroppers and traffic analysis
- DC protocol (dining cryptographers)

*** Cryptographic Voting
- focus: ballot box anonymity
- credentials for voting
- issues of double voting, security, robustness, efficiency

*** Digital Cash
- focus: privacy in transactions, purchases
- unlinkable credentials
- blinded notes
- "digital coins" may not be possible

*** Crypto Anarchy
- using the above to evade govUt., to bypass tax collection,
etc.
- a technological solution to the problem of too much
government


*** G L O S S A R Y    ***


*** agoric systems -- open, free market systems in which
voluntary transactions are central.

*** Alice and Bob -- cryptographic protocols are often made
clearer by considering parties A and B, or Alice and Bob,
performing some protocol. Eve the eavesdropper, Paul the
prover, and Vic the verifier are other common stand-in names.

*** ANDOS -- all or nothing disclosure of secrets.

*** anonymous credential -- a credential which asserts
some right or privilege or fact without revealing the identity
of the holder.  This is unlike CA driver's licenses.

*** asymmetric cipher -- same as public key
cryptosystem.

*** authentication -- the process of verifying an identity
or credential, to ensure you are who you said you were.

*** biometric security -- a type of authentication using
fingerprints, retinal scans, palm prints, or other
physical/biological signatures of an individual.

*** bit commitment -- e.g., tossing a coin and then
committing to the value without being able to change the
outcome. The blob is a cryptographic primitive for this.

*** blinding, blinded signatures -- A signature that the
signer does not remember having made.  A blind signature is
always a cooperative protocol and the receiver of the
signature provides the signer with the blinding information.

*** blob -- the crypto equivalent of a locked box. A
cryptographic primitive for bit commitment, with the
properties that a blobs can represent a 0 or a 1, that others
cannot tell be looking whether itUs a 0 or a 1, that the creator
of the blob can "open" the blob to reveal the contents, and that
no blob can be both a 1 and a 0. An example of this is a flipped
coin covered by a hand.

*** channel -- the path over which messages are
transmitted. Channels may be secure or insecure, and may
have eavesdroppers (or enemies, or disrupters, etc.) who alter
messages, insert and delete messages, etc. Cryptography is
the means by which communications over insecure channels
are protected.

*** chosen plaintext attack -- an attack where the
cryptanalyst gets to choose the plaintext to be enciphered,
e.g., when possession of an enciphering machine or algorithm
is in the possession of the cryptanalyst.

*** cipher -- a secret form of writing, using substitution or
transposition of characters or symbols.

*** ciphertext -- the plaintext after it has been encrypted.

*** code -- a restricted cryptosystem where words or
letters of a message are replaced by other words chosen from
a codebook. Not part of modern cryptology, but still useful.

*** coin flipping -- an important crypto primitive, or
protocol, in which the equivalent of flipping a fair coin is
possible. Implemented with blobs.

*** collusion -- wherein several participants cooperate to
deduce the identity of a sender or receiver, or to break a
cipher. Most cryptosystems are sensitive to some forms of
collusion. Much of the work on implementing DC Nets, for
example, involves ensuring that colluders cannot isolate
message senders and thereby trace origins and destinations
of mail.

*** computationally secure -- where a cipher cannot be
broken with available computer resources, but in theory can
be broken with enough computer resources. Contrast with
unconditionally  secure.

*** countermeasure -- something you do to thwart an
attacker.

*** credential -- facts or assertions about some entity. For
example, credit ratings, passports, reputations, tax status,
insurance records, etc.  Under the current system, these
credentials are increasingly being cross-linked. Blind
signatures may be used to create anonymous credentials.

*** credential clearinghouse  -- banks, credit agencies,
insurance companies, police departments, etc., that correlate
records and decide the status of records.

*** cryptanalysis -- methods for attacking and breaking
ciphers and related cryptographic systems. Ciphers may be
broken, traffic may be analyzed, and passwords may be
cracked. Computers are of course essential.

*** crypto anarchy -- the economic and political system
after the deployment of encryption, untraceable e-mail,
digital pseudonyms, cryptographic voting, and digital cash. A
pun on "crypto," meaning "hidden," and as when Gore Vidal
called William F. Buckley a "crypto fascist."

*** cryptography -- another name for cryptology.

*** cryptology -- the science and study of writing, sending,
receiving, and deciphering secret messages. Includes
authentication, digital signatures, the hiding of messages
(steganography), cryptanalysis, and several other fields.

*** cyberspace  -- the electronic domain, the Nets, and
computer-generated spaces. Some say it is the "consensual
reality" described in "Neuromancer." Others say it is the phone
system. Others have work to do.

*** DC protocol, or DC-Net -- the dining cryptographers
protocol. DC-Nets use multiple participants communicating
with the DC protocol.

*** DES -- the Data Encryption Standard, proposed in
1977 by the National Bureau of Standards (now NIST), with
assistance from the National Security Agency. Based on the
"Lucifer" cipher developed by Horst Feistel at IBM, DES is a
secret key cryptosystem that cycles 64-bit blocks of data
through multiple permutations with a 56-bit key controlling
the routing. "Diffusion" and "confusion" are combined to form
a cipher that has not yet been cryptanalyzed (see "DES,
Security of"). DES is in use for interbank transfers, as a
cipher inside of several RSA-based systems, and is available
for PCs.

*** DES, Security of  -- many have speculated that the NSA
placed a trapdoor (or back door) in DES to allow it to read
DES-encrypted messages. This has not been proved. It is
known that the original Lucifer algorithm used a 128-bit key
and that this key length was shortened to 64 bits (56 bits
plus 8 parity bits), thus making exhaustive search much
easier (so far as is known, brute-force search has not been
done, though it should be feasible today). Shamir and Bihan
have used a technique called "differential cryptanalysis" to
reduce the exhaustive search needed for chosen plaintext
attacks (but with no import for ordinary DES).

*** differential cryptanalysis -- the Shamir-Biham
technique for cryptanalyzing DES. With a chosen plaintext
attack, they've reduced the number of DES keys that must be
tried from about 2^56 to about 2^47 or less. Note, however,
that rarely can an attacker mount a chosen plaintext attack
on DES systems.

*** digital cash, digital money -- Protocols for
transferring value, monetary or otherwise, electronically.
Digital cash usually refers to systems that are anonymous.
Digital money systems can be used to implement any quantity
that is conserved, such as points, mass, dollars, etc.  There
are many variations of  digital money systems, ranging from
VISA numbers to blinded signed digital coins.  A topic too
large for a single glossary entry.

*** digital pseudonym -- basically, a "crypto identity." A
way for individuals to set up accounts with various
organizations without revealing more information than they
wish. Users may have several digital pseudonyms, some used
only once, some used over the course of many years. Ideally,
the pseudonyms can be linked only at the will of the holder. In
the simplest form, a public key can serve as a digital
pseudonym and need not be linked to a physical identity.

*** digital signature --  Analogous to a written signature
on a document. A modification to a message that only the
signer can make but that everyone can recognize.  Can  be used
legally to contract at a distance.

*** digital timestamping -- one function of a digital
notary public, in which some message (a song, screenplay, lab
notebook, contract, etc.) is stamped with a time that cannot
(easily) be forged.

*** dining cryptographers protocol (aka DC protocol,
DC nets) -- the untraceable message sending system
invented by David Chaum. Named after the "dining
philosophers" problem in computer science, participants form
circuits and pass messages in such a way that the origin
cannot be deduced, barring collusion. At the simplest level,
two participants share a key between them. One of them
sends some actual message by bitwise exclusive-ORing the
message with the key, while the other one just sends the key
itself. The actual message from this pair of participants is
obtained by XORing the two outputs. However, since nobody
but the pair knows the original key, the actual message
cannot be traced to either one of the participants.

*** discrete logarithm problem -- given integers a, n,
and x, find some integer m such that a^m mod n = x, if m
exists. Modular exponentiation, the a^m mod n part, is
straightforward (and special purpose chips are available), but
the inverse problem is believed to be very hard, in general.
Thus it is conjectured that modular exponentiation is a one-
way function.

*** DSS, Digital Signature Standard -- the latest NIST
(National Institute of Standards and Technology, successor to
NBS) standard for digital signatures. Based on the El Gamal
cipher, some consider it weak and poor substitute for RSA-
based signature schemes.

*** eavesdropping, or passive wiretapping --
intercepting messages without detection. Radio waves may be
intercepted, phone lines may be tapped, and computers may
have RF emissions detected. Even fiber optic lines can be
tapped.

*** factoring -- Some large numbers are difficult to factor.
It is conjectured that there are no feasible--i.e."easy," less
than exponential in size of number-- factoring methods. It is
also an open problem whether RSA may be broken more easily
than by factoring the modulus (e.g., the public key might
reveal information which simplifies the problem).
Interestingly, though factoring is believed to be "hard", it is
not known to be in the class of NP-hard problems. Professor
Janek invented a factoring device, but he is believed to be
fictional.

*** information-theoretic security -- "unbreakable"
security, in which no amount of cryptanalysis can break a
cipher or system. One time pads are an example (providing the
pads are not lost nor stolen nor used more than once, of
course). Same as unconditionally secure.

*** key -- a piece of information needed to encipher or
decipher a message. Keys may be stolen, bought, lost, etc.,
just as with physical keys.

*** key exchange, or key distribution -- the process of
sharing a key with some other party, in the case of symmetric
ciphers, or of distributing a  public key in an asymmetric
cipher. A major issue is that the keys be exchanged reliably
and without compromise. Diffie and Hellman devised one such
scheme, based on the discrete logarithm problem.

*** known-plaintext attack -- a cryptanalysis of a cipher
where plaintext-ciphertext pairs are known. This attack
searches for an unknown key. Contrast with the chosen
plaintext attack, where the cryptanalyst can also choose the
plaintext to be enciphered.

*** mail, untraceable  -- a system for sending and
receiving mail without traceability or observability.
Receiving mail anonymously can be done with broadcast of the
mail in encrypted form.  Only the intended recipient (whose
identity, or true name, may be unknown to the sender) may
able to decipher the message. Sending mail anonymously
apparently requires mixes or use of the dining cryptographers
(DC) protocol.

*** minimum disclosure proofs  -- another name for zero
knowledge proofs, favored by Chaum.

*** mixes -- David Chaum's term for a box which performs
the function of mixing, or decorrelating, incoming and
outgoing electronic mail messages. The box also strips off
the outer envelope (i.e., decrypts with its private key) and
remails the message to the address on the inner envelope.
Tamper-resistant modules may be used to prevent cheating
and forced disclosure of the mapping between incoming and
outgoing mail. A sequence of many remailings effectively
makes tracing sending and receiving impossible. Contrast this
with the software version, the DC protocol.

*** modular exponentiation  -- raising an integer to the
power of another integer, modulo some integer. For integers
a, n, and m, a^m mod n. For example, 5^3 mod 100 = 25. Modular
exponentiation can be done fairly quickly with a sequence of
bit shifts and adds, and special purpose chips have been
designed. See also discrete logarithm.

*** National Security Agency (NSA)  -- the largest
intelligence agency, responsible for making and breaking
ciphers, for intercepting communications, and for ensuring
the security of U.S. computers. Headquartered in Fort Meade,
Maryland, with many listening posts around the world.  The
NSA funds cryptographic research and advises other agencies
about cryptographic matters. The NSA once obviously had the
world's leading cryptologists, but this may no longer be the
case.

*** negative credential -- a credential that you possess
that you don't want any one else to know, for example, a
bankruptcy filing.  A formal version of a negative reputation.

*** NP-complete -- a large class of difficult problems.
"NP" stands for nondeterministic polynomial time, a class of
problems thought in general not to have feasible algorithms
for their solution.  A problem is "complete"  if  any other NP
problem may be reduced to that problem.   Many important
combinatorial and algebraic problems are NP-complete: the
traveling salesman problem, the Hamiltonian cycle problem,
the word problem, and on and on.

*** oblivious transfer -- a cryptographic primitive that
involves the probabilistic transmission of bits. The sender
does not know if the bits were received.

*** one-time pad -- a string of randomly-selected bits or
symbols which is combined with a plaintext message to
produce the ciphertext. This combination may be shifting
letters some amount, bitwise exclusive-ORed, etc.). The
recipient, who also has a copy of the one time pad, can easily
recover the plaintext. Provided the pad is only used once and
then destroyed, and is not available to an eavesdropper, the
system is perfectly secure, i.e., it is information-
theoretically secure. Key distribution (the pad)  is obviously a
practical concern, but consider CD-ROM's.

*** one-way function -- a function which is easy to
compute in one direction but hard to find any inverse for, e.g.
modular exponentiation, where the inverse problem is known
as the discrete logarithm problem. Compare the special case
of trap door one-way functions.  An example of  a one-way
operation is multiplication: it is  easy to multiply two
prime numbers of 100 digits to produce a 200-digit number,
but  hard to factor that 200-digit number.

*** P ?=? NP  -- Certainly the most  important unsolved
problem in complexity theory. If P = NP, then cryptography as
we know it today does not exist.  If P = NP,  all NP problems
are "easy."

*** padding -- sending extra messages to confuse
eavesdroppers and to defeat traffic analysis.   Also adding
random bits to a message to be enciphered.

*** plaintext -- also called cleartext, the text that is to be
enciphered.

*** Pretty Good Privacy (PGP)  -- Phillip ZimmermanUs
implementation of RSA, recently upgraded to version 2.0,
with more robust components and several new features. RSA
Data Security has threatened PZ so he no longer works on it.
Version 2.0 was written by a consortium of non-U.S. hackers.

*** prime numbers -- integers with no factors other than
themselves and 1. The number of primes is unbounded.  About
1% of the 100 decimal digit numbers are prime.  Since there
are about 10^70 particles in the universe, there are about
10^23  100 digit primes for each and every particle in the
universe!

*** probabilistic encryption  -- a scheme by Goldwasser,
Micali, and Blum that allows multiple ciphertexts for the
same plaintext, i.e., any given plaintext may have many
ciphertexts if the ciphering is repeated. This protects against
certain types of known ciphertext attacks on RSA.

*** proofs of identity -- proving who you are, either your
true name, or your digital identity. Generally, possession of
the right key is sufficient proof (guard your key!). Some work
has been done on "is-a-person" credentialling agencies, using
the so-called Fiat-Shamir protocol...think of this as a way to
issue unforgeable digital passports. Physical proof of identity
may be done with biometric security methods. Zero knowledge
proofs of identity reveal nothing beyond the fact that the
identity is as claimed. This has obvious uses for computer
access, passwords, etc.

*** protocol -- a formal procedure for solving some
problem. Modern cryptology is mostly about the study of
protocols for many problems, such as coin-flipping, bit
commitment (blobs), zero knowledge proofs, dining
cryptographers, and so on.

*** public key -- the key distributed publicly to potential
message-senders. It may be published in a phonebook-like
directory or otherwise sent. A major concern is the validity
of this public key to guard against spoofing or impersonation.

*** public key cryptosystem -- the modern breakthrough
in cryptology, designed by Diffie and Hellman, with
contributions from several others. Uses trap door one-way
functions so that encryption may be done by anyone with
access to the "public key" but decryption may be done only by
the holder of the "private key." Encompasses public key
encryption, digital signatures, digital cash, and many other
protocols and applications.

*** public key encryption -- the use of modern
cryptologic methods to provided message security and
authentication. The RSA algorithm is the most widely used
form of public key encryption, although other systems exist.
A public key may be freely published, e.g., in phonebook-like
directories, while the corresponding private key is closely
guarded.

*** public key patents  -- M.I.T. and Stanford, due to the
work of Rivest, Shamir, Adleman, Diffie, Hellman, and Merkle,
formed Public Key Partners to license the various public key,
digital signature, and RSA patents. These patents, granted in
the early 1980s, expire in the between 1998 and 2002. PKP
has licensed RSA Data Security Inc., of Redwood City, CA,
which handles the sales, etc.

*** quantum cryptography -- a system based on quantum-
mechanical principles. Eavesdroppers alter the quantum state
of the system and so are detected. Developed by Brassard and
Bennett, only small laboratory demonstrations have been
made.

*** reputations -- the trail of positive and negative
associations and judgments that some entity accrues. Credit
ratings, academic credentials, and trustworthiness are all
examples. A digital pseudonym will accrue these reputation
credentials based on actions, opinions of others, etc. In
crypto anarchy, reputations and agoric systems will be of
paramount importance. There are many fascinating issues of
how reputation-based systems work, how credentials can be
bought and sold, and so forth.

*** RSA -- the main public key encryption algorithm,
developed by Ron Rivest, Adi Shamir, and Kenneth Adleman. It
exploits the difficulty of factoring large numbers to create a
private key and public key. First invented in 1978, it remains
the core of modern public key systems. It is usually much
slower than DES, but special-purpose modular exponentiation
chips will likely speed it up. A popular scheme for speed is to
use RSA to transmit session keys and then a high-speed
cipher like DES for the actual message text.
*** Description -- Let p and q be large primes, typically
with more than 100 digits. Let n = pq and find some e such that
e is relatively prime to (p - 1)(q - 1). The set of numbers p, q,
and e is the private key for RSA. The set of numbers n and e
forms the public key (recall that knowing n is not sufficient to
easily find p and q...the factoring problem).  A message M is
encrypted by computing M^e mod n. The owner of the private key
can decrypt the encrypted message by exploiting number theory
results, as follows. An integer d is computed such that ed = 1
(mod (p - 1)(q - 1)).  Euler proved a theorem that M^(ed) = M
mod n and so M^(ed) mod n = M. This means that in some sense
the integers e and d are "inverses" of each other. [If this
is unclear, please see one of the many texts and articles on
public key encryption.]

*** secret key cryptosystem -- A system which uses the
same key to encrypt and decrypt traffic at each end of a
communication link.  Also called a symmetric or one-key
system.  Contrast with public key cryptosystem.

*** smart cards -- a computer chip embedded in credit
card.  They can hold cash, credentials, cryptographic keys,
etc. Usually these are built with some degree of tamper-
resistance. Smart cards may perform part of a crypto
transaction, or all of it. Performing part of it may mean
checking the computations of a more powerful computer, e.g.,
one in an ATM.

*** spoofing, or masquerading -- posing as another user.
Used for stealing passwords, modifying files, and  stealing
cash. Digital signatures and other authentication methods are
useful to prevent this. Public keys must be validated and
protected to ensure that others don't substitute their own
public keys which users may then unwittingly use.

*** steganography -- a part of cryptology dealing with
hiding messages and obscuring who is sending and receiving
messages. Message traffic is often padded to reduce the
signals that would otherwise come from a sudden beginning
of messages.

*** symmetric cipher -- same as private key
cryptosystem.

*** tamper-responding modules, tamper-resistant
modules (TRMs) -- sealed boxes or modules which are hard
to open, requiring extensive probing and usually leaving ample
evidence that the tampering has occurred. Various protective
techniques are used, such as special metal or oxide layers on
chips, armored coatings, embedded optical fibers, and other
measures to thwart analysis. Popularly called "tamper-proof
boxes." Uses include: smart cards, nuclear weapon initiators,
cryptographic key holders, ATMs, etc.

*** tampering, or active wiretapping -- interfering with
messages and possibly modifying them. This may compromise
data security, help to break ciphers, etc.  See also spoofing.

*** token -- some representation, such as ID cards, subway
tokens, money, etc., that indicates possession of some
property or value.

*** traffic analysis -- determining who is sending or
receiving messages by analyzing packets, frequency of
packets, etc. A part of steganography. Usually handled with
traffic padding.

*** transmission rules -- the protocols for determining
who can send messages in a DC protocol, and when. These
rules are needed to prevent collision and deliberate jamming
of the channels.

*** trap messages -- dummy messages in DC Nets which
are used to catch jammers and disrupters. The messages
contain no private information and are published in a blob
beforehand so that the trap message can later be opened to
reveal the disrupter. (There are many strategies to explore
here.)

*** trap-door -- In cryptography, a piece of secret
information that allows the holder of a private key to invert a
normally hard to invert function.

*** trap-door one way functions -- functions which are
easy to compute in both the forward and reverse direction but
for which the disclosure of an algorithm to compute the
function in the forward direction does not provide
information on how to compute the function in the reverse
direction. More simply put, trap-door one way functions are
one way for all but the holder of the secret information. The
RSA algorithm is the best-known example of such a function.

*** unconditional security -- same as information-
theoretic security, that is, unbreakable except by loss or
theft of the key.

*** unconditionally  secure -- where no amount of
intercepted ciphertext is enough to allow the cipher to be
broken, as with the use of a one-time pad cipher. Contrast
with computationally secure.

*** voting, cryptographic -- Various schemes have been
devised for anonymous, untraceable voting. Voting schemes
should have several properties: privacy of the vote, security
of the vote (no multiple votes), robustness against disruption
by jammers or disrupters, verifiability (voter has confidence
in the results), and efficiency.

*** zero knowledge proofs -- proofs in which no
knowledge of the actual proof is conveyed. Peggy the Prover
demonstrates to Sid the Skeptic that she is indeed in
possession of some piece of knowledge without actually
revealing any of that knowledge. This is useful for access to
computers, because eavesdroppers or dishonest sysops cannot
steal the knowledge given. Also called minimum disclosure
proofs. Useful for proving possession of some property, or
credential, such as age or voting status, without revealing
personal information.

--
..........................................................................
Timothy C. May         | Crypto Anarchy: encryption, digital money,
[e-mail]       | anonymous networks, digital pseudonyms, zero
408-688-5409           | knowledge, reputations, information markets,
W.A.S.T.E.: Aptos, CA  | black markets, collapse of governments.
Higher Power: 2^756839 | PGP Public Key: by arrangement.



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From: David Sobel <[e-mail]>
To: Cypherpunks <[e-mail]>
Date: Wed, 11 Aug 1993 13:59:53 EST
Subject: Clipper trapdoor?
Status: OR

  Clipper trapdoor?

Peter Wayner <[e-mail]> writes:

>My general impression is that the system is secure. Many people
>have played paranoid and expressed concerns that the classified
>algorithm might be hiding a trapdoor. It became clear to me that
>these concerns were really silly. There is a built-in trapdoor
>to be used by the government when it is "legal authorized" to
>intercept messages. The NSA has rarely had trouble in the past
>exercising either its explicitly granted legal authority  or
>its implied authority. The phrase "national security" is a
>powerful pass phrase around Washington and there is no reason
>for me to believe that the NSA wouldn't get all of the access
>to the escrow database that it needs to do its job. Building in
>a backdoor would only leave a weakness for an opponent to exploit
>and that is something that is almost as sacrilidgeous at the NSA
>as just putting the classified secrets in a Fed Ex package to
>Saddam Hussein.

This raises an interesting question and I draw a totally different
conclusion.  If, as we have been told, the only way for an agency to
obtain the escrow keys is to present a court order, than NSA needs
to obtain such an order to decrypt *any* communication it intercepts.

I don't really understand what Peter means when he says that "NSA has
rarely had trouble in the past exercising either its explicitly granted
legal authority  or its implied authority. The phrase 'national security'
is a powerful pass phrase around Washington and there is no reason
for me to believe that the NSA wouldn't get all of the access
to the escrow database that it needs to do its job."

Does this mean NSA would, in fact, obtain a warrant in order to "get all
of the access to the escrow database that it needs to do its job"?  If so,
this would represent an unprecedented change in the way NSA does "its
job."  NSA has no domestic law enforcement authority, so it would
obviously never be in a position to obtain a law enforcement wiretap
warrant under Title III.  The only possible way for NSA to obtain a warrant
would be under the Foreign Intelligence Surveillance Act (FISA).  But the
Foreign Intelligence Surveillance Court, which issues warrants under FISA,
has ruled that FISA's provisions

   limit the authority to conduct electronic surveillances to the U.S.
   in a geographic sense as defined in sec. 101(i).  The drafters left
   to another day the matter of "broadening this legislation to apply
   overseas ... because the problems and circumstances of overseas
   surveillance demand separate treatment."

In the Matter of the Application of the United States for an Order
Authorizing
the Physical Search of Nonresidential Premises and Personal Property (1981),
footnote 1 (citations omitted).

Consider the following hypothetical: Iraqi agents smuggle Clipper phones
out of the U.S.  Saddam Hussein uses them to communicate with his military
commander in Basra.  NSA intercepts the communications.  Question:  How
does NSA decrypt the messages?

Note that neither Title III (law enforcement) nor FISA (U.S.-based) apply
to this situation, so we have to assume that NSA will not have a court order
to obtain the escrow keys.  I have to conclude that NSA would not be putting
this technology out into the world *unless* it did, in fact, have some way
to
decrypt messages *without* access to the escrow keys.

Am I missing something?


David Sobel
CPSR Legal Counsel




Article 18507 of sci.crypt:
Path: lynx.unm.edu!fmsrl7!destroyer!sol.ctr.columbia.edu!math.ohio-state.edu!da
From: [e-mail]
Newsgroups: sci.crypt
Subject: SKIPJACK Review, Interim Report
Message-ID: <[e-mail]>
Date: 1 Aug 93 22:09:27 -0400
Distribution: world
Organization: Georgetown University
Lines: 369

                            SKIPJACK Review

                             Interim Report

                        The SKIPJACK Algorithm


           Ernest F. Brickell, Sandia National Laboratories
               Dorothy E. Denning, Georgetown University
            Stephen T. Kent, BBN Communications Corporation
                          David P. Maher, AT&T
                  Walter Tuchman, Amperif Corporation

                              July 28, 1993

                            (copyright 1993)


Executive Summary

The objective of the SKIPJACK review was to provide a mechanism whereby
persons outside the government could evaluate the strength of the
classified encryption algorithm used in the escrowed encryption devices
and publicly report their findings.  Because SKIPJACK is but one
component of a large, complex system, and because the security of
communications encrypted with SKIPJACK depends on the security of the
system as a whole, the review was extended to encompass other
components of the system.  The purpose of this Interim Report is to
report on our evaluation of the SKIPJACK algorithm.  A later Final
Report will address the broader system issues.

The results of our evaluation of the SKIPJACK algorithm are as
follows:

  1. Under an assumption that the cost of processing power is halved
     every eighteen months, it will be 36 years before the cost of
     breaking SKIPJACK by exhaustive search will be equal to the cost
     of breaking DES today.  Thus, there is no significant risk that
     SKIPJACK will be broken by exhaustive search in the next 30-40
     years.

  2. There is no significant risk that SKIPJACK can be broken through a
     shortcut method of attack.

  3. While the internal structure of SKIPJACK must be classified in
     order to protect law enforcement and national security objectives,
     the strength of SKIPJACK against a cryptanalytic attack does not
     depend on the secrecy of the algorithm.



1.  Background

On April 16, the President announced a new technology initiative aimed
at providing a high level of security for sensitive, unclassified
communications, while enabling lawfully authorized intercepts of
telecommunications by law enforcement officials for criminal
investigations.  The initiative includes several components:

    A classified encryption/decryption algorithm called "SKIPJACK."

    Tamper-resistant cryptographic devices (e.g., electronic chips),
    each of which contains SKIPJACK, classified control software, a
    device identification number, a family key used by law enforcement,
    and a device unique key that unlocks the session key used to
    encrypt a particular communication.

    A secure facility for generating device unique keys and programming
    the devices with the classified algorithms, identifiers, and keys.

    Two escrow agents that each hold a component of every device unique
    key.  When combined, those two components form the device unique
    key.

    A law enforcement access field (LEAF), which enables an authorized
    law enforcement official to recover the session key.  The LEAF is
    created by a device at the start of an encrypted communication and
    contains the session key encrypted under the device unique key
    together with the device identifier, all encrypted under the family
    key.

    LEAF decoders that allow an authorized law enforcement official to
    extract the device identifier and encrypted session key from an
    intercepted LEAF.  The identifier is then sent to the escrow
    agents, who return the components of the corresponding device
    unique key.  Once obtained, the components are used to reconstruct
    the device unique key, which is then used to decrypt the session
    key.

This report reviews the security provided by the first component,
namely the SKIPJACK algorithm.  The review was performed pursuant to
the President's direction that "respected experts from outside the
government will be offered access to the confidential details of the
algorithm to assess its capabilities and publicly report their
finding."  The Acting Director of the National Institute of Standards
and Technology (NIST) sent letters of invitation to potential
reviewers.  The authors of this report accepted that invitation.

We attended an initial meeting at the Institute for Defense Analyses
Supercomputing Research Center (SRC) from June 21-23.  At that meeting,
the designer of SKIPJACK provided a complete, detailed description of
the algorithm, the rationale for each feature, and the history of the
design.  The head of the NSA evaluation team described the evaluation
process and its results.  Other NSA staff briefed us on the LEAF
structure and protocols for use, generation of device keys, protection
of the devices against reverse engineering, and NSA's history in the
design and evaluation of encryption methods contained in SKIPJACK.
Additional NSA and NIST staff were present at the meeting to answer our
questions and provide assistance.  All staff members were forthcoming
in providing us with requested information.

At the June meeting, we agreed to integrate our individual evaluations
into this joint report.  We also agreed to reconvene at SRC from July
19-21 for further discussions and to complete a draft of the report.
In the interim, we undertook independent tasks according to our
individual interests and availability.  Ernest Brickell specified a
suite of tests for evaluating SKIPJACK.  Dorothy Denning worked at NSA
on the refinement and execution of these and other tests that took into
account suggestions solicited from Professor Martin Hellman at Stanford
University.  NSA staff assisted with the programming and execution of
these tests.  Denning also analyzed the structure of SKIPJACK and its
susceptibility to differential cryptanalysis.  Stephen Kent visited NSA
to explore in more detail how SKIPJACK compared with NSA encryption
algorithms that he already knew and that were used to protect
classified data.  David Maher developed a risk assessment approach
while continuing his ongoing work on the use of the encryption chip in
the AT&T Telephone Security Device.  Walter Tuchman investigated the
anti-reverse engineering properties of the chips.

We investigated more than just SKIPJACK because the security of
communications encrypted with the escrowed encryption technology
depends on the security provided by all the components of the
initiative, including protection of the keys stored on the devices,
protection of the key components stored with the escrow agents, the
security provided by the LEAF and LEAF decoder, protection of keys
after they have been transmitted to law enforcement under court order,
and the resistance of the devices to reverse engineering.  In addition,
the success of the technology initiative depends on factors besides
security, for example, performance of the chips.  Because some
components of the escrowed encryption system, particularly the key
escrow system, are still under design, we decided to issue this Interim
Report on the security of the SKIPJACK algorithm and to defer our Final
Report until we could complete our evaluation of the system as a
whole.


2.  Overview of the SKIPJACK Algorithm

SKIPJACK is a 64-bit "electronic codebook" algorithm that transforms a
64-bit input block into a 64-bit output block.  The transformation is
parameterized by an 80-bit key, and involves performing 32 steps or
iterations of a complex, nonlinear function.  The algorithm can be used
in any one of the four operating modes defined in FIPS 81 for use with
the Data Encryption Standard (DES).

The SKIPJACK algorithm was developed by NSA and is classified SECRET.
It is representative of a family of encryption algorithms developed in
1980 as part of the NSA suite of "Type I" algorithms, suitable for
protecting all levels of classified data.  The specific algorithm,
SKIPJACK, is intended to be used with sensitive but unclassified
information.

The strength of any encryption algorithm depends on its ability to
withstand an attack aimed at determining either the key or the
unencrypted ("plaintext") communications.  There are basically two
types of attack, brute-force and shortcut.


3.  Susceptibility to Brute Force Attack by Exhaustive Search

In a brute-force attack (also called "exhaustive search"), the
adversary essentially tries all possible keys until one is found that
decrypts the intercepted communications into a known or meaningful
plaintext message.  The resources required to perform an exhaustive
search depend on the length of the keys, since the number of possible
keys is directly related to key length.  In particular, a key of length
N bits has 2^N possibilities.  SKIPJACK uses 80-bit keys, which means
there are 2^80 (approximately 10^24) or more than 1 trillion trillion
possible keys.

An implementation of  SKIPJACK optimized for a single processor on the
8-processor Cray YMP performs about 89,000 encryptions per second.  At
that rate, it would take more than 400 billion years to try all keys.
Assuming the use of all 8 processors and aggressive vectorization, the
time would be reduced to about a billion years.

A more speculative attack using a future, hypothetical, massively
parallel machine with 100,000 RISC processors, each of which was
capable of 100,000 encryptions per second, would still take about 4
million years.  The cost of such a machine might be on the order of $50
million.  In an even more speculative attack, a special purpose machine
might be built using 1.2 billion $1 chips with a 1 GHz clock.  If the
algorithm could be pipelined so that one encryption step were performed
per clock cycle, then the $1.2 billion machine could exhaust the key
space in 1 year.

Another way of looking at the problem is by comparing a brute force
attack on SKIPJACK with one on DES, which uses 56-bit keys.  Given that
no one has demonstrated a capability for breaking DES, DES offers a
reasonable benchmark.  Since SKIPJACK keys are 24 bits longer than DES
keys, there are 2^24 times more possibilities.  Assuming that the cost
of processing power is halved every eighteen months, then it will not
be for another 24 * 1.5 = 36 years before the cost of breaking
SKIPJACK is equal to the cost of breaking DES today.  Given the lack of
demonstrated capability for breaking DES, and the expectation that the
situation will continue for at least several more years, one can
reasonably expect that SKIPJACK will not be broken within the next
30-40 years.

Conclusion 1:   Under an assumption that the cost of processing power
is halved every eighteen months, it will be 36 years before the cost of
breaking SKIPJACK by exhaustive search will be equal to the cost of
breaking DES today.  Thus, there is no significant risk that SKIPJACK
will be broken by exhaustive search in the next 30-40 years.

4.  Susceptibility to Shortcut Attacks

In a shortcut attack, the adversary exploits some property of the
encryption algorithm that enables the key or plaintext to be determined
in much less time than by exhaustive search.  For example, the RSA
public-key encryption method is attacked by factoring a public value
that is the product of two secret primes into its primes.

Most shortcut attacks use probabilistic or statistical methods that
exploit a structural weakness, unintentional or intentional (i.e., a
"trapdoor"), in the encryption algorithm.  In order to determine
whether such attacks are possible, it is necessary to thoroughly
examine the structure of the algorithm and its statistical properties.
In the time available for this review, it was not feasible to conduct
an evaluation on the scale that NSA has conducted or that has been
conducted on the DES.  Such review would require many man-years of
effort over a considerable time interval.  Instead, we concentrated on
reviewing NSA's design and evaluation process.  In addition, we
conducted several of our own tests.

4.1  NSA's Design and Evaluation Process

SKIPJACK was designed using building blocks and techniques that date
back more than forty years.  Many of the techniques are related to work
that was evaluated by some of the world's most accomplished and famous
experts in combinatorics and abstract algebra.  SKIPJACK's more
immediate heritage dates to around 1980, and its initial design to
1987.

SKIPJACK was designed to be evaluatable, and the design and evaluation
approach was the same used with algorithms that protect the country's
most sensitive classified information.  The specific structures
included in SKIPJACK have a long evaluation history, and the
cryptographic properties of those structures had many prior years of
intense study before the formal process began in 1987.  Thus, an
arsenal of tools and data was available.  This arsenal was used by
dozens of adversarial evaluators whose job was to break SKIPJACK.  Many
spent at least a full year working on the algorithm.  Besides highly
experienced evaluators, SKIPJACK was subjected to cryptanalysis by less
experienced evaluators who were untainted by past approaches.  All
known methods of attacks were explored, including differential
cryptanalysis.  The goal was a design that did not allow a shortcut
attack.

The design underwent a sequence of iterations based on feedback from
the evaluation process.  These iterations eliminated properties which,
even though they might not allow successful attack, were related to
properties that could be indicative of vulnerabilities.  The head of
the NSA evaluation team confidently concluded "I believe that SKIPJACK
can only be broken by brute force   there is no better way."

In summary, SKIPJACK is based on some of NSA's best technology.
Considerable care went into its design and evaluation in accordance
with the care given to algorithms that protect classified data.

4.2  Independent Analysis and Testing

Our own analysis and testing increased our confidence in the strength
of SKIPJACK and its resistance to attack.

4.2.1  Randomness and Correlation Tests

A strong encryption algorithm will behave like a random function of the
key and plaintext so that it is impossible to determine any of the key
bits or plaintext bits from the ciphertext bits (except by exhaustive
search).  We ran two sets of tests aimed at determining whether
SKIPJACK is a good pseudo random number generator.  These tests were
run on a Cray YMP at NSA.  The results showed that SKIPJACK behaves
like a random function and that ciphertext bits are not correlated with
either key bits or plaintext bits.  Appendix A gives more details.

4.2.2  Differential Cryptanalysis

Differential cryptanalysis is a powerful method of attack that exploits
structural properties in an encryption algorithm.  The method involves
analyzing the structure of the algorithm in order to determine the
effect of particular differences in plaintext pairs on the differences
of their corresponding ciphertext pairs, where the differences are
represented by the exclusive-or of the pair.  If it is possible to
exploit these differential effects in order to determine a key in less
time than with exhaustive search, an encryption algorithm is said to be
susceptible to differential cryptanalysis.  However, an actual attack
using differential cryptanalysis may require substantially more chosen
plaintext than can be practically acquired.

We examined the internal structure of SKIPJACK to determine its
susceptibility to differential cryptanalysis.  We concluded it was not
possible to perform an attack based on differential cryptanalysis in
less time than with exhaustive search.

4.2.3  Weak Key Test

Some algorithms have "weak keys" that might permit a shortcut
solution.  DES has a few weak keys, which follow from a pattern of
symmetry in the algorithm.  We saw no pattern of symmetry in the
SKIPJACK algorithm which could lead to weak keys.  We also
experimentally tested the all "0" key (all 80 bits are "0") and the all
"1" key to see if they were weak and found they were not.

4.2.4  Symmetry Under Complementation Test

The DES satisfies the property that for a given plaintext-ciphertext
pair and associated key, encryption of the one's complement of the
plaintext with the one's complement of the key yields the one's
complement of the ciphertext.  This "complementation property" shortens
an attack by exhaustive search by a factor of two since half the keys
can be tested by computing complements in lieu of performing a more
costly encryption.  We tested SKIPJACK for this property and found that
it did not hold.

4.2.5  Comparison with Classified Algorithms

We compared the structure of SKIPJACK to that of NSA Type I algorithms
used in current and near-future devices designed to protect classified
data.  This analysis was conducted with the close assistance of the
cryptographer who developed SKIPJACK and included an in-depth
discussion of design rationale for all of the algorithms involved.
Based on this comparative, structural analysis of SKIPJACK against
these other algorithms, and a detailed discussion of the similarities
and differences between these algorithms, our confidence in the basic
soundness of SKIPJACK was further increased.

Conclusion 2:  There is no significant risk that SKIPJACK can be broken
through a shortcut method of attack.


5.   Secrecy of the Algorithm

The SKIPJACK algorithm is sensitive for several reasons.  Disclosure of
the algorithm would permit the construction of devices that fail to
properly implement the LEAF, while still interoperating with legitimate
SKIPJACK devices.  Such devices would provide high quality
cryptographic security without preserving the law enforcement access
capability that distinguishes this cryptographic initiative.
Additionally, the SKIPJACK algorithm is classified SECRET   NOT
RELEASABLE TO FOREIGN NATIONALS.  This classification reflects the high
quality of the algorithm, i.e., it incorporates design techniques that
are representative of algorithms used to protect classified
information.  Disclosure of the algorithm would permit analysis that
could result in discovery of these classified design techniques, and
this would be detrimental to national security.

However, while full exposure of the internal details of SKIPJACK would
jeopardize law enforcement and national security objectives, it would
not jeopardize the security of encrypted communications.  This is
because a shortcut attack is not feasible even with full knowledge of
the algorithm.  Indeed, our analysis of the susceptibility of SKIPJACK
to a brute force or shortcut attack was based on the assumption that
the algorithm was known.

Conclusion 3:  While the internal structure of SKIPJACK must be
classified in order to protect law enforcement and national security
objectives, the strength of SKIPJACK against a cryptanalytic attack
does not depend on the secrecy of the algorithm.



Article 18517 of sci.crypt:
Path: lynx.unm.edu!fmsrl7!destroyer!gatech!concert!rutgers!att-out!cbnewsh!cbne
From: [e-mail] (Bill Stewart [phone])
Newsgroups: sci.crypt
Subject: Re: SKIPJACK Review, Interim Report
Message-ID: <[e-mail]>
Date: 2 Aug 93 09:30:53 GMT
References: <[e-mail]>
 <23i6hm$[e-mail]>
Sender: [e-mail] (NetNews Administrator)
Organization: Electronic Birdwatching Society
Lines: 57
In-Reply-To: [e-mail]'s message of 2 Aug 1993 04:52:0
Nntp-Posting-Host: rainier.ho.att.com

Thanks to Dr. Denning for posting the interim report.  On a brief read-through,
I haven't got much substantive to say yet, so I'll depart from my
normal procedures and not say much :-)  Three concerns, though:
- While it's good that the whole system is being evaluated and not
 just Skipjack, I'm concerned about the propaganda value of
 releasing a report that says "the committee says it's just fine",
 while will presumably be abused in attempts to railroad
 standards committees into specifying Clipper.
- While the analysis looked at the design techniques for SkipJack
 and other classified algorithms, it did *not* address the issue of
 why, if SkipJack is so strong, it's only approved for unclassfied
 material, while the other algorithms can be used for classified.
 Is it weaker in some way?  Key length alone doesn't count...
- Key length adequacy - DES can be brute-forced now, at substantial expense;
 two different designs have been published for ~$30M, 1-day search.
 The report makes a big deal about how 24 bits longer key means
 about 36 years longer life if computer power keeps doubling every
 1.5 years, though it's speculative how long that will continue,
 and makes a big deal about how 80-bit keys are unsearchable now.
 An 80-bit key is still vulnerable in most of our lifetimes;
 a 128-bit key really is not.

In article <23i6hm$[e-mail]> [e-mail]
   >Additionally, the SKIPJACK algorithm is classified SECRET   NOT
   >RELEASABLE TO FOREIGN NATIONALS.  This classification reflects the high
   >quality of the algorithm, i.e., it incorporates design techniques that
   >are representative of algorithms used to protect classified
   >information.  Disclosure of the algorithm would permit analysis that
   >could result in discovery of these classified design techniques, and
   >this would be detrimental to national security.

   Wasn't it a Dr. Denning that said secrecy of algorithms should NOT be
  used to build secure cryto?  History certainly indicates this.
   Is all of our crypto based on a house of cards?

She's making another point here - this is using secrecy to prevent
*other* people from building secure crypto, not just to obscure
current crypto algorithms.  However, calling that "detrimental to
national security" would be blatant political propaganda.....

Realistically, though, there may have been design mistakes in current
crypto algorithms used for classified information; the NSA isn't
infallible, and they may have missed something.  And disclosing the
algorithm would increase the possibility of any mistakes being discovered.

   >However, while full exposure of the internal details of SKIPJACK would
   >jeopardize law enforcement and national security objectives, it would

I notice that this refers to "national security objectives" rather
than "national security", and doesn't say *who* set these objectives.

More later...
--
#    Pray for peace;      Bill
# Bill Stewart 1-908-949-0705 [e-mail] AT&T Bell Labs 4M312 Holmdel N
# White House Comment Line 1-202-456-1111  fax [phone]
# ROT-13 public key available upon request


Article 18525 of sci.crypt:
Newsgroups: sci.crypt
Path: lynx.unm.edu!fmsrl7!ukma!usenet.ins.cwru.edu!agate!library.ucla.edu!ddsw1
From: [e-mail] (George Mitchell)
Subject: Re: SKIPJACK Review, Interim Report
Message-ID: <[e-mail]>
Organization: Test Systems Strategies, Inc., Beaverton, Oregon
References: <[e-mail]>
Date: Mon, 2 Aug 1993 17:03:06 GMT
Lines: 35

Thank you, Dr. Denning, for posting the Skipjack report in a timely
manner.  On the whole, it looks like good news.  In particular, I was
happy to see these paragraphs:

>5.   Secrecy of the Algorithm

>The SKIPJACK algorithm is sensitive for several reasons.  Disclosure of
>the algorithm would permit the construction of devices that fail to
>properly implement the LEAF, while still interoperating with legitimate
>SKIPJACK devices.  Such devices would provide high quality
>cryptographic security without preserving the law enforcement access
>capability that distinguishes this cryptographic initiative.
[. . .]
>However, while full exposure of the internal details of SKIPJACK would
>jeopardize law enforcement and national security objectives, it would
>not jeopardize the security of encrypted communications.  This is
>because a shortcut attack is not feasible even with full knowledge of
>the algorithm.  Indeed, our analysis of the susceptibility of SKIPJACK
>to a brute force or shortcut attack was based on the assumption that
>the algorithm was known.

>Conclusion 3:  While the internal structure of SKIPJACK must be
>classified in order to protect law enforcement and national security
>objectives, the strength of SKIPJACK against a cryptanalytic attack
>does not depend on the secrecy of the algorithm.

Why did this make me so happy, when I am generally so displeased
with the Clipper initiative and the key-escrow scheme?

Because the disclosure of the Skipjack algorithm is INEVITABLE.

You can bet that {the top bad guys of the moment} will pry loose
the algorithm within a year.  While they may not be public-spirited
enough to immediately release it to the rest of us, eventually
someone will.                -- George Mitchell ([e-mail])





Joining the EFF
by Esther Dyson
Publisher of Release 1.0

The Electronic Frontier Foundation is probably best--but incorrectly--
known as "Mitch Kapor's organization to defend computer hackers." In
fact, the basic message of the Foundation, "There's a new world coming.
Let's make sure it has rules we can live with." These rules will
establish the rights and also the responsibilities of the users of the
electronic infrastructure- which means, eventually, all of us.

The Foundation's most visible efforts, yes, involve the defense of
people charged with various forms of electronic trespass and damage.
This is not to say that there's no such thing as illegal hacking, but
that not all hacking is illegal. Many hackers' rights are abridged when
they are arrested by government agents who don't understand how a
computer works. There's a certain fear of the unknown that makes people
suspect the worst of a supposed "computer criminal." Searches have been
overly broad, and charges ridiculously overstated. Moreover, innocent
bystanders are hurt too, when bulletin boards are closed down and their
means of communication with each other is disrupted.

Sentences are also unduly harsh: Consider the proposed prohibition on
Robert Riggs' use of a computer after his release from prison.  The
computer is not a magic, deadly instrument but rather something closer
to a telephone. Many criminals plan their crimes by telephone or even
commit telephone farud, but they don't get barred from telephone usage
thereafter. Says EFF: "Such restrictions tend to promote the notion that
computers are inherently dangerous...[and that] access [to them falls
properly within the scope of government action."

The EFF also advocates government funding for the National Research and
Education Network, and passage of bills to do 80 currently in the Senate
and House. That doesn't mean that NREN would be the only thing going,
but it would be a spur to and resource for private efforts. Certainly
such a network should exist, but what's the best way to get it done?
Should access be subsidized for the poor or distant, as it was for
telephone service and still is for postal service? Should the subsidies
be direct, or should they go to users, or should they be achieved
through regulation?

Perhaps these questions don't have absolute answers, just as the
telephone business has evolved through variety of forms (not always
gracefully, to be sure). Perhaps we should start with a subsidized
network that ultimately will pay its way!  Although the EFF has
positions on these issues, its major concern is that the public take
part in addressing them, rather than leaving decisions up to a handful
of bureaucrats and interested parties.

Beyond that, there are important issues to consider and resolve, such as
the definition and protection of Constitutional rights including
privacy, free speech and assembly. In some cases, its more important to
have laws that are clear than precisely what those laws are. The world
can adjust to most laws, as long as they make some sense and are
consistent. Most interesting right now is the delicate tension over the
classification of network services such as Compuserve and Prodigy.  Are
they publishers, liable for the information they disseminate, or
utilities and common carriers, required to carry anything for the public
at large -and therefore not liable for its content? Or is this a false
dichotomy (as AMIX's Phil Salin asserts): For example, a BBS might be
like a bookstore: free to select the books it stocks and sells, but not
responsible for their content individually (i.e., for libel, say).  Nor
is the bookstore responsible for what anyone says inside its walls. Yet
some "adult" bookstores and record stores have been closed by local
legal actions. The precedents are muddy.

Finally, there's the awkward question of how to make the network good
for people without stuffing culture down unwilling throats.  If you
believe that broadcast TV is mostly junk and public TV is mostly
subsidized culture for the well-off, how do we make networks a people's
medium - real global villages rather than a global TV set or a global
museum? Will people use them to communicate rather than vegetate if you
make it easy? Can we regain the community involvement people lost when
everything became too big and complicated? Are citizens' groups working
over the net fringe groups, or are they harbingers of how everyone could
get involved?

I came to this with the benign American assumption that anyone
apprehended by the police has probably done something wrong; spending
time in Eastern Europe, watching the LA police videos and learning about
some of the EFF cases have changed my perspective forever.

I am now a board member of the EFF. But don't worry, Release 1.0 won't
become a mouthpiece for the EFF. In fact, when Mitch Kapor asked me to
join, I responded that I was pleased and flattered, but not sure I
should join; I certainly don't agree with all the views of the other
board members. "That," said Mitch, "is the point."

In other words, I joined the EFF to help set its agenda, not just to
help carry it out. and so I strongly urge that you get involved too.

Esther Dyson is the Editor and publisher of Release 1.0, a newsletter
covering the computer industry, from which this article is reproduced by
permission.




From [e-mail] Sun Aug  1 16:02:48 1993
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From: Julian Dibbell <[e-mail]>
Message-Id: <[e-mail]>
Subject: Village Voice sidebars
To: [e-mail]
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Here are the two short sidebars that accompany the Village Voice article on
Cypherpunks et al. Posted by and with the permission of the author.

The first contains some of the more practical information that Tim May was
wondering about, though it does not point anyone towards ftp sites, mailing
lists, or anything as concrete as that. I didn't know whether you all would
appreciate an influx of "left-biased" :-) crypto-naifs flooding in here as a
result of my posting the list address, so I refrained. Also didn't think
advertising locations for PGP was a good idea, given the legal hassles that
might result to people doing the distribution. But if any of you think I was
being overscrupulous, I encourage you to write the Voice with further
information and I will do my best to see the letter gets published.

BUILDING A BETTER MONKEY WRENCH

Contrary to the conventional wisdom of an age gone cuckoo for ``smart''
technology, Luddism is neither dead nor beside the point -- it's just gotten
smarter. The Cypherpunks and other cryptography hackers are model
practitioners of a new, techno-savvy Luddism, implementing and popularizing
sophisticated gadgets that could short-circuit the awesome surveillance
capabilities built into cyberspace without harming its equally awesome power
to connect individuals. Long-term, these brave new tools will do more to
keep Big Brother out of your business than any legislation can, so you owe
yourself at least a cursory understanding of how they work. The following
primer should jump-start you. Read it and get smart.

PUBLIC-KEY CRYPTOGRAPHY: Most encryption schemes require sender and receiver
to agree on a secret encoding number, or key, before communication. This
increases vulnerability, since that first message establishing the key can't
itself be encrypted. Public-key systems, invented in 1975 by Ur-cypherpunk
Whitfield Diffie along with Martin Hellman, have no such requirement, making
them ideal for the highly snoopable channels of computer networks. In
public-key crypto, everybody creates two keys, one published for all the
world to read, and one kept absolutely secret. Whatever's encrypted with the
first can only be unlocked with the second. Thus, if you want to send
someone a secret message there's no need to make prior contact -- you just
look up that person's public key and use it to encrypt the text. Current
usage: The free public-key encryption program PGP is one of the most
popularly deployed crypto tools in the on-line world, with PGP public keys
rapidly becoming the electronic superhighway's equivalent of vanity plates.

ANONYMOUS REMAILERS: These systems aim to conceal not the contents of a
message but its source. A remailer is a network-connected computer that
takes in e-mail, then sends it on to a destination specified in attached,
encrypted instructions, thus placing a veil between sender and receiver. If
the message is sent through a chain of even a few remailers, the veil
quickly becomes rock solid, guaranteeing the sender's anonymity. Current
usage: The Cypherpunks maintain a working anonymous remailer chain, but the
most active are the one-hop systems used by participants in public on-line
discussions of bondage, foot worship, and assorted other predilections they
might not want their computer-literate boss/parents/neighbors to know
about.

DIGITAL SIGNATURES: In the fluid world of digital info, how do you verify
that a message is really from whom it claims it's from? Turn public-key
cryptography inside out, that's how. Have the sender encrypt the message
with her private key, then let the receiver try to decrypt it with the
sender's public key. If the decryption comes out clear, then the sender's
identity is confirmed -- without revealing her private key or even, if the
public key is attached to a pseudonymous but otherwise trustworthy on-line
persona, her physical identity. This is more or less how digital signatures
work. Current usage: mainly in corporate and bureaucratic settings, though
all good Cypherpunks try to make a habit of e-signing their e-mail.

ELECTRONIC CASH: Imagine the convenience of credit cards combined with the
anonymity of cash. Imagine a microchip-equipped debit card that instantly
deducts transactions from the user's bank account, yet does so without
revealing the payer's identity to the payee or linking payer and payee in
the bank's records. Imagine these mechanisms set loose in the world's
computer nets, converting great chunks of money supply into fast, loose,
digital e-cash. The wizardry of public-key crypto can make all this happen
and probably will. Current usage: experimental, mostly. Denmark, however, is
gearing up to implement an encrypted smart-card system, based on the ideas
of crypto-hacker David Chaum, who holds patents on most e-money
applications.

--

TALE FROM THE CRYPTO WARS

The high weirdness of the military's code-busting censorship moves peaked in
World War II, but didn't end there. It was during the Gulf War, in fact,
that military censors made one of the strangest additions to their already
strange list of banned communications: the Navajo language. A small number
of Navajos, it seems, wanted to send broadcast greetings in their native
tongue to loved ones stationed overseas, but Armed Forces Radio refused to
pass the messages along. Once again, the mere possibility of enemy signals
lurking in the noise was too much for the censors to bear. ``We have a
responsibility to control what's on the radio,'' said the lieutenant colonel
in charge, ``and if I don't know what it says then I can't control it.''

    In the ripest of ironies, however, it turns out that the only nation
ever known to have used Navajo as a cover for secret communications was the
United States itself. Throughout World War II's Pacific campaign, the Marine
Corps made heavy and effective use of its Navajo codetalker units--teams of
Navajo radiomen who spoke a slangy, cryptic patois difficult even for
uninitiated Navajos to grasp, and ultimately impossible for the Japanese to
decode. Today the codetalkers remain legendary figures on the rez and beyond
-- legendary enough indeed that New Mexico congressman Bill Richardson,
wielding the memory of their exploits, finally shamed Armed Forces Radio
into lifting its ban and letting Navajo greetings reach the Gulf.

    It's a familiar story. Prized and feared for its impenetrable otherness,
Navajo has met the same uneasy fate reserved for all true difference in a
country that both prides itself on cultural diversity and insistently
suppresses it. But in its blurring of the lines between language and secret
code, Navajo's passage through the belly of the military beast hints at one
way out of America's terminal cultural ambivalence. As arch-Cypherpunk John
Gilmore has argued, committing to universally accessible encryption is one
way for our society to finally take the ideal of diversity seriously --
backing it up ``with physics and mathematics, not with laws,'' and certainly
not with the lip service it's traditionally honored with. Cryptography could
guarantee us each a language of our own, which no censor, military or
otherwise, could hope to silence.



--
*********************************************************************
Julian Dibbell                                       [e-mail]
*********************************************************************




From [e-mail] Thu Aug  5 22:11:35 1993
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From: [e-mail] (Timothy C. May)
Message-Id: <[e-mail]>
Subject: (fwd) Re: Will SKIPJACK's algorithm get out? (Non-technical)
To: [e-mail]
Date: Thu, 5 Aug 93 20:47:25 PDT
X-Mailer: ELM [version 2.3 PL11]
Status: OR

Here's a posting I did on how Skipjack (which I deliberately called
"Clipjack") can be likely broken by groups like ours. The anonymous
remailers, and the alt.whistleblowing group, can be used to publish
details of the whole Skipjack/Capstone/Mykotronx/MYK-78/etc. ball of
wax as they become available.

Whether we can actually be the ones to analyze the chips or not is
immaterial: spreading reports that Clipjack is vulnerable will be
useful disinformation (reduced confidence, fewer commercial sales,
more acceptance of more provably strong software-based alternatives,
etc.)

-Tim


Newsgroups: sci.crypt,alt.privacy.clipper
From: [e-mail] (Timothy C. May)
Subject: Re: Will SKIPJACK's algorithm get out? (Non-technical)
Message-ID: <[e-mail]>
Date: Fri, 6 Aug 1993 03:36:27 GMT


Larry Loen ([e-mail]) wrote:

: Myself, I confidently expect to see Skipjack published in some Eurocrypt
: proceedings or other in the next 4 or 5 years, especially if the darn thing
: is actually produced in any volumes.  There is a decidely
: different attitude in W. Europe towards this sort of thing.

: It's mostly a question of economics.  Will someone, somewhere put out the
: bucks to do a "tear down" of the chip and figure out how it works.  I could
: imagine some crypto company in Europe doing just that and being also motivate
: to publish what they find for competitive reasons. . .

Some of us plan to do just this: once "Clipjack" phones are finalized
and on sale and/or Mykotronx is selling finalized chips, they'll be
looked at.

I once ran Intel's electron-beam testing lab, so I have some
familiarity with looking at chips, including ostensibly
tamper-resistant modules. VLSI Technology is fabbing the chips, using
a process said to be quite tamper-resistant. We'll see. (While
publishing the algorithm may or may not be illegal, there's no
reasonable law saying you can't look at something, unless perhaps it's
formally classified....will the Clipjack chips have "Top Secret"
stamped on them? Somehow I can't quite picture this in phones sold
across the country and outside!)

(I'm not saying it'll be easy to do this reverse-engineering, mind
you.  Between mechanical barriers to access (carbide-like particles in
the packaging compound to deter grinding), complex-chemistry epoxies
to deter plasma- and chemical-decapping, various chip-level
countermeasures (storing bits on floating gates, using multiple layers
of metal, etc.), the access to the die surface may be very difficult.
The "smartcard" chip makers have led the way in devising
tamper-resistant chip processes, though their task is quite a bit
easier (stopping access to an active chip on an active smartcard, to
modify the money amounts) than Clipjack faces (stopping any
examination of the chip topology and programming which would reveal
the algorithms used)

But given enough samples, enough time, and some
commitment, the secrets of Clipjack will fall.)

As a "Cypherpunk" (cf. cover of "Wired" #2, "Whole Earth Review" Summer '93,
and the current (8-2-93) "Village Voice" cover story), I see no reason
not to publish the details. This'll let other folks build phones and other
comm systems which spoof or defeat the Clipjack system, especially the
disgusting and thoroughly un-American "key escrow" system.

Naturally, we'll use our "anonymous remailers" (multiple reroutings of
messages, with each node decrypting with its key and passing on what's
left to the next chosen node....diffusion and confusion, a la Chaum's
1981 "CACM" paper on "digital mixes") to protect ourselves. No sense
taking chances that the Feds will view our "liberation" efforts with
disfavor and hit us with charges they devise (violations of Munitions
Act, RICO, sedition, etc.). This is how some of our members were able
to "liberate" secret Mykotoxin documents from the dumpsters of
Mykotoxin (something the Supremes have said is OK for law enforcement
to do, by the way) and post them anonymously to our mailing list (I
believe these docs were then posted to alt.whistleblowers, but they were
only _mentioned_ on sci.crypt, not actually posted).

I expect at least _three_ separate groups are preparing to break the
Clipjack algorithm, at least as embodied in the Clipper/Skipjack chips
that come on the market.

Breaking the system also allows independent observers to see if it
does in fact contain deliberate weaknesses (though the focus on
"weaknesses" is secondary to the basic issue of "key escrow" as a
concept--it is key escrow, especially mandatory key escrow, that is
the real issue. (Mandatory key escrow is not yet part of law, to be
fair, but still "in the wind"...we won't really know for a few more
years whether the "voluntary" key escrow system will become mandatory)

It'll also be interesting to see how Clipjack phone customers react to
the revelations of the algorithms.
(CLIPJACK.CRK 88%), (H)elp, (F)ind, (P)gUp, (T)op, (>), More?

Crypto anarchy means never having to say you're sorry.


Yours in the struggle,

-Tim May
--
..........................................................................
Timothy C. May         | Crypto Anarchy: encryption, digital money,
[e-mail]       | anonymous networks, digital pseudonyms, zero
408-688-5409           | knowledge, reputations, information markets,
W.A.S.T.E.: Aptos, CA  | black markets, collapse of governments.
Higher Power: 2^756839 | Public Key: PGP and MailSafe available.
Note: I put time and money into writing this posting. I hope you enjoy it.



From [e-mail] Tue May 25 13:02:18 1993
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To: [e-mail]
Subject: Bill O' Rights
From: [e-mail] (Paul Ferguson)
Message-Id: <[e-mail]>
Date: Tue, 25 May 93 14:13:42 EDT
Organization: Sytex Communications, Inc
Status: OR

I remember reading this in the March ACM and thinking,"Man. He hit
that right on the head." When I ran across this transcript in Computer
Select earlier this morning (while looking for various encryption
products, no less), I thought those of you who had not already seen it
would be struck by John Perry's insights. BTW, I also have the full
transcripts of Dorothy Denning's, William A. Bayse's (Assistant
Director, FBI Technical Services Division) and Lewis M. Branscomb's
(Harvard University) articles which appeared in the same issue with
regards to Digital Telephony, if anyone cares for me to post them.
Looking back on the progression of events, beginning with the debate
of the Digital Telephony proposal and subsequently the proposal
currently (officially) referred to as the "Key Escrow" Chip (and its
associated escrow scheme), I can't help but surmise that the whole
ball of wax is geared towards allowing the Government the ability to
effectively eavesdrop on its citizens communications in the face of
advancing technology, without regard to privacy matters.

8<---- Begin forwarded text ---------

Journal:    Communications of the ACM  March 1993 v36 n3 p21(3)
* Full Text COPYRIGHT Association for Computing Machinery Inc.1993.
----------------------------------------------------------------------
Title:    Bill o' rights. (impact of technology on basic civil rights;
   humor) (Electronic Frontier)
Author:   Barlow, John Perry

----------------------------------------------------------------------
Full Text:

*Note*    Only Text is presented here; see printed issues for graphics.

It has been almost three years since I first heard of the Secret Service
raids on Steve Jackson Games and the cyberurchins from the Legion of
Doom.  These federal exploits, recently chronicled in Bruce Sterling's
book Hacker Crackdown, precipitated the formation of the Electronic
Frontier Foundation and kicked loose an international digital liberties
movement which is still growing by leaps and conferences.

I am greatly encouraged by the heightened awareness among the citizens
of the Global Net of our rights, responsibilities, and opportunities.
I am also heartened that so many good minds now tug at the legal,
ethical, and social riddles which come from digitizing every damned
thing.  The social contract of Cyberspace is being developed with
astonishing rapidity, considering that we are still deaf, dumb, and
disembodied in here.

Meanwhile, back in the Physical World, I continue to be haunted by the
words of the first lawyer I called on behalf of Steve Jackson, Phiber
Optik, and Acid Phreak back in the spring of 1990.  This was Eric
Lieberman of the prestigious New York civil liberties firm Rabinowitz,
Boudin, Standard, Krinsky, and Lieberman.  I told him how the Secret
Service had descended on my acquaintances and taken every scrap of
circuitry or magnetized oxide they could find.  This had included not
only computers and disks, but clock radios and audio cassettes.

I told him that, because no charges had been filed, the government was
providing their targets no legal opportunity to recoup their confiscated
equipment and data.  (In fact, most of the victims of Operation Sun
Devil still have neither been charged nor had their property returned to
them.)

[This issue has been somewhat resolved with the recent ruling in
 favor of Steve Jackson and the subsequent award of damages.]

The searches were anything but surgical and the seizures appeared
directed less at gathering evidence than inflicting punishment without
the bothersome formality of a trial.  I asked Lieberman if the Secret
Service might not be violating the Fourth Amendment's assurance of "The
right of the people to be secure in their persons, houses, papers, and
effects, against unreasonable searches and seizures."

He laughed bitterly.  "I think if you take a look at case law for the
last ten years or so, you will find that the Fourth Amendment has
pretty much gone away," he said.

I did.  He was right.  A lot of what remained of it was flushed a year
later when the Rehnquist Court declared that in the presence of
"probable cause" ...a phrase of inviting openness...law enforcement
officials could search first and obtain warrants later.

Furthermore, I learned that through such sweeping prosecutorial
enablements as RICO and Zero Tolerance, the authorities could entract
their own unadjudicated administrative "fines" by keeping much of what
they seized for their own uses.

(This incentive often leads to disproportionalities between "punishment"
and "crime" which even Kafka might have found a bit over the top.  I
know of one case in which the DEA acquired a $14 million Gulfstream
bizjet from a charter operator because one of its clients left half a
gram of cocaine in its washroom.)

I tried to image a kind of interactive Bill of Rights in which
amendments would fade to invisibility as they became meaningless, but
I knew that was hardly necessary.  The citizens of Stalin's Soviet
Union had a constitutional guarantee of free expression which
obviously, like our own, allowed some room for judicial
interpretation.

It occurred to me then that a more honest approach might be to maintain
a concordant Bill of Rights, running in real time and providing
up-to-the-minute weather reports from the federal bench, but I never got
around to it.

Recently I started thinking about it again.  These thoughts were
inspired partly by Dorothy Denning's apology for the FBI's digital
telephony proposal (which appears in this issue).  I found her analysis
surprisingly persuasive, but I also found it fundamentally based on an
assumption I no longer share: the ability of the Bill of Rights to
restrain government, now or in the future.

The men who drafted the U.S.  Constitution and its first ten amendments
knew something that we have largely forgotten: Governments exist to limit
freedom.  That's their job.  And to the extent that utterly unbridled
liberty seems to favor the reptile in us, a little government is not
such a bad thing.  But it never knows when to quit.  As there is no
limit to either human imagination or creativity in the wicked service
of the Self, so it is always easy for our official protectors to envision
new atrocities to prevent.

Knowing this, James Madison and company designed a government which was
slightly broken up front.  They intentionally created a few wrenches to
cast into the works, and these impediments to smooth governmental
operation were the Bill of Rights.

Lately though, we find ourselves living in a world where the dangers we
perceive are creatures of information rather than experience.  Since
the devil one knows is always less fearsome than the worst one can
imagine, there is no limit to how terrifying or potent these dangers can
seem.

Very few of us, if any, have ever felt the malign presence of a real,
live terrorist or drug lord or Mafia capo or dark-side hacker.  They
are projected into our consciousness by the media and the government,
both of which profit directly from our fear of them.  These enemies are,
in our (tele)visions of them, entirely lacking in human decency or
conscience. There is no reason they should be mollycoddled with
constitutional rights.

And so, we have become increasingly willing to extend to government what
the Founding Fathers would not: real efficiency.  The courts have been
updating the Bill of Rights to fit modern times and perils, without
anyone having to go through the cumbersome procedure of formal amendment.

The result, I would suggest with only a little sarcasm or hyperbole, has
come to look something like this:

Bill O' Rights

AMENDMENT 1

Congress shall encourage the practice of Judeo-Christian religion by its
own public exercise thereof and shall make no laws abridging the freedom
of responsible speech, unless such speech is in a digitized form or
contains material which is copyrighted, classified, proprietary, or
deeply offensive to non-Europeans, nonmales, differently abled or
alternatively preferenced persons; or the right of the people peaceably
to assemble, unless such assembly is taking place on corporate or
military property or within an electronic environment, or to make
petitions to the government for a redress of grievances, unless those
grievances relate to national security.

AMENDMENT 2

A well-regulated militia having become irrelevant to the security of the
state, the right of the people to keep and bear arms against one another
shall nevertheless remain uninfringed, excepting such arms as may be
afforded by the poor or those perferred by drug pushers, terrorists, and
organized criminals, which shall be banned.

AMENDMENT 3

No soldier shall, in time of peace, be quartered in any house, without
the consent of the owner, unless that house is thought to have been used
for the distribution of illegal substances.

AMENDMENT 4

The right of the people to be secure in their persons, houses, papers and
effects against unreasonable searches and seizures, may be suspended to
protect public welfare, and upon the unsupported suspicion of law
enforcement officials, any place or conveyance shall be subject to
immediate search, and any such places or conveyances or property within
them may be permanently confiscated without further judicial proceeding.

AMENDMENT 5

Any person may be held to answer for a capital, or otherwise infamous
crime involving illicit substances, terrorism, or child pornography, or
upon any suspicion whatever; and may be subject for the same offense to
be twice put in jeopardy of life or limb, once by the state courts and
again by the federal judiciary; and may be compelled by various means,
including the forced submission of breath samples, bodily fluids, or
encryption keys, to be a witness against himself, refusal to do so
constituting an admission of guilt; and may be deprived of life, liberty,
or property without further legal delay; and any property thereby
forfeited shall be dedicated to the discretionary use of law enforcement
agencies.

AMENDMENT 6

In all criminal prosecutions, the accused shall enjoy the right to a
speedy and private plea bargaining session before pleading guilty.  He is
entitled to the assistance of underpaid and indifferent counsel to
negotiate his sentence, except where such sentence falls under federal
mandatory sentencing requirements.

AMENDMENT 7

In suits at common law, where the contesting parties have nearly
unlimited resources to spend on legal fees, the right of trail by jury
shall be preserved.

AMENDMENT 8

Sufficient bail may be required to ensure that dangerous criminals will
remain in custody, where cruel punishments are usually inflicted.

AMENDMENT 9

The enumeration in the Constitution of certain rights, shall not be
construed to deny or disparage others which may be asserted by the
government as required to preserve public order, family values, or
national security.

AMENDMENT 10

The powers not delegated to the U.S.  by the Constitution, shall be
reserved to the U.S.  Departments of Justice and Treasury, except when
the states are willing to forsake federal funding.

[John P. Barlow is a technological author and the cofounder (with Mitch
Kapor) of the Electronic Frontier Foundation.  He currently lives in
Wyoming, New York and "in Cyberspace." His email address is barlow
@eff.org.]

Paul Ferguson               |  The future is now.
Network Integrator          |  History will tell the tale;
Centreville, Virginia USA   |  We must endure and struggle
[e-mail]             |  to shape it.

   Stop the Wiretap (Clipper/Capstone) Chip.



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To: [e-mail]
Subject: NSA: The Eyes of Big Brother
From: [e-mail] (Paul Ferguson)
Message-Id: <[e-mail]>
Date: Sun, 01 Aug 93 20:44:54 EDT
Organization: Sytex Communications, Inc
Status: OR

reprinted without permission from Claustrophobia:

Claustrophobia
August 1993
Volume 2, Number 7



NSA: The Eyes of Big Brother
by Charles Dupree

-----------------------------------------------------------

The historical of the National Security Agency (NSA) presented
here includes and depends on information reported in three books.
The vast majority of data on the National Security Agency comes
from James Bamford's book The Puzzle Palace [1982]; all
quotations are taken from Bamford unless otherwise noted. As Tim
Weiner says, this book is "The best -- the only -- history of the
NSA." Material about NSA's secret funding comes entirely from
Weiner's Blank Check [1990], which also provided budget estimates
and supporting material for other sections. The CIA and the Cult
of Intelligence by Victor Marchetti and John D. Marks [1980
edition, originally published 1974], provided background
information and a glimpse of the NSA from within the intelligence
community but outside the agency itself.
--------------------------------------------------------------

The oppressive atmosphere of Orwell's 1984 arises from the
omnipresence of Big Brother, the symbol of the government's
concern for the individual. Big Brother controls the language,
outlawing words he dislikes and creating new words for his
favorite concepts. He can see and hear nearly everything, public
or private. Thus he enforces a rigid code of speech and action
that erodes the potential for resistance and reduces the need for
force. As Noam Chomsky says, propaganda is to democracy what
violence is to totalitarianism. Control thoughts, and you can
easily control behavior.

U.S. history affords a prime example in the era named after
Senator Joseph McCarthy, though he had many supporters in his
attack on freedom of thought and speech. Perhaps his most
powerful friend was J. edgar Hoover, who fed him material from
Federal Bureau of Investigation (FBI) files (some of it true)
which  he used to attack individuals for their supposed political
leanings. By the time of Watergate, the Central Intelligence
Agency (CIA) had become at least as notorious as the FBI, due
largely to its assassinations of foreign leaders and support for
military coups around the world.

The Creation of the NSA

Budgetary authority for the National Security Agency (NSA)
apparently comes from the Central Intelligence Act of 1949. This
act provides the basis for the secret spending program known as
the black budget by allowing any arm of the government to
transfer money to the CIA "without regard to any provisions of
the law," and allowing the CIA to spend its funds as it sees fit,
with no need to account for them.

Congress passed the C.I.A. Act despite the fact that only the
ranking members of the Senate and House Armed Services Committees
knew anything about its contents; the remaining members of
Congress were told that open discussion, or even clear
explanation, of the bill would be counterproductive. There were
complaints about the secrecy; but in the end the bill passed the
House by a vote of 348-4, and the Senate by a majority voice
vote.

The NSA's estimated $10 billion annual allocation (as of 1990) is
funded entirely through the black budget. Thus Congress
appropriates funds for the NSA not only without information on
the agency's plans, but without even a clear idea of the amount
it appropriates; and it receives no accounting of the uses to
which the funds were put. This naturally precludes any debate
about the direction or management of such agencies, effectively
avoiding public oversight while spending public funds. (Weiner
notes the analogy to "Taxation without representation.")

Watching and Listening

"The NSA has also spent a great deal of time and money spying on
American citizens. For 21 years after its inception it tracked
every telegram and telex in and out of the United States, and
monitored the telephone conversations of the politically
suspect." (Weiner, Blank Check)

Due to its unique ability to monitor communications within the
U.S. without a warrant, which the FBI and CIA cannot legally do,
NSA becomes the center of attempts to spy on U.S. citizens.
Nominally this involves only communications in which at least one
terminal is outside the U.S., but in practice target lists have
often grown to include communications between U.S. citizens
within the country. And political considerations have sometimes
become important.

During the Nixon administration, for example, various agencies
(e.g., FBI, CIA, Secret Service) requested that the NSA provide
all information it encountered showing that foreign governments
were attempting to influence or controls activities of U.S.
anti-war groups, as well as information on civil rights, draft
resistance/evasion support groups, radical-related media
activities, and so on, "where such individuals have some foreign
connection," probably not that uncommon given the reception such
groups usually receive at home. Clearly it would have been
illegal for those agencies to gather such information themselves
without warrants, but they presumably believed that the NSA was
not similarly restricted when they included on their watch lists
such as Nixonian bugaboos as Eldridge Cleaver, Abbie Hoffman,
Jane Fonda, Joan Biaz, Dr. Benjamin Spock, and the Rev. ralph
Abernathy. Presumably the name of Dr, Martin Luther King, Jr.,
was removed from the list the year Nixon was elected; certainly
it was a targeted name before that time.

It is not feasible to determine in advance which telegrams and
telephone calls will be among those the NSA is tasked with
intercepting. Therefore, the NSA is normally reduced to recording
all traffic on lines it is monitoring, and screening this traffic
(by computer when possible) to catch targeted communications.
This is called the "vacuum-cleaner approach."

Also basic to this method is the "watch list" of groups and
individuals whose communications should be "targeted." When a
target is added to the watch list, NSA's computers are told to
extract communications to, from, or about the target; the agency
can then examine the selected communications and determine
whether they constitute intelligence data.

This list of targets usually expands to include all members of
targeted groups plus individuals and groups with whom they
communicate; thus it has a tendency to grow rapidly if not
checked. Some requests seems a bit astonishing: during the
presidency of Richard Nixon, a Quaker, J. Edgar Hoover requested
"complete surveillance of all Quakers in the United States"
because he thought they were shipping food and supplies to
Southeast Asia.

Project Shamrock

Project Shamrock was initiated in 1945 by the Signal Security
Agency (SSA), which eventually merged into the NSA. Until the
project was terminated in 1975 to prevent investigation, Shamrock
involved NSA (and its predecessors) in communications collection
activities that would be illegal for agencies such as the CIA or
FBI.

Under Shamrock, the international branches of RCA, ITT, and
Western Union provided access by SSA, and its successor NSA, to
certain telegrams sent by those companies. each company's counsel
recommended against involvement on legal grounds; each company
requested the written opinion of the Attorney General that it was
not making itself liable to legal action. However, none of them
received anything in writing from anyone in the government, and
they all cooperated without it. (They did get a verbal assurance
from the first Secretary of Defense, James Forrestal, who said he
was speaking for the President; thus they may have been concerned
at his resignation just over a year later, his hospitalization
within a week suffering from depression, anxiety, and paranoia,
and his suicide less than two months later.)

As Shamrock grew, and the NSA began to develop its own means of
intercepting communications, the watch list approach became the
accepted standard, since nothing less was effective or
worthwhile. the intelligence community became aware that it could
enter a name on the watch list more or less at will, and it would
soon receive the requested material, marked classified, and
gathered in within (or perhaps under cover of) the law.

The Huston Plan

The Huston Plan, formally known as "Domestic Intelligence
Gathering Plan: Analysis and Strategy," was submitted in July
1970 to President Nixon. The goal of the plan was to relax some
restrictions on intelligence gathering, apparently those of NSCID
No. 6. Some parts of the intelligence community felt that these
relaxations would assist their efforts. The proposals included:

o allowing the NSA to monitor "communications of U.S. citizens
using international facilities" (presumably facilities located in
the U.S., since the NSA already had authority to monitor such
communications if at least one terminal was outside U.S.
territory)

o intensifying "coverage of individuals and groups in the United
States who pose a major threat to the internal security"

o modifying restrictions "to permit selective use of
[surreptitious entry] against other urgent and high priority
internal security targets" as well as to procure "vitally needed
foreign cryptographic material," which would have required the
FBI to accept warrantless requests for such entries from other
agencies ("Use of this technique is clearly illegal: it amounts
to burglary. It is also highly risky and could result in great
embarrassment if exposed. However, it is also the most fruitful
tool and can produce the type of intelligence which cannot be
obtained in any other fashion.")

President Nixon approved this plan over the objection of J. Edgar
Hoover and without the knowledge of Attorney General Mitchell.
Hoover went to Mitchell, who had been left out of the entire
process, and was consequently angry; Mitchell convinced Nixon to
withdraw his approval 13 days after giving it.

Project Minaret

The size and complexity of the domestic watch list program became
a problem, since it bordered on illegality. Project Minaret was
established on July 1, 1969, to "privid[e] more restrictive
control" on the domestic products, and "to restrict the knowledge
that information is being collected and processed by the National
Security Agency." The agency knew it was close to legal
boundaries, and wanted to protect itself.

Minaret continued until the fall of 1973, when Attorney General
Richardson became aware of the domestic watch list program and
ordered such activities stopped. As the Watergate drama played
out, Congress began to hear about the NSA's projects, and within
two years formally inquiring about them

Uncontrolled Activities

Like most  intelligence agencies, the NSA uses words such as
"interrupt" and "target" in a technical sense with a precise but
often classified definition. This specialized language makes it
difficult to legislate or oversee the activities involved. For
instance, in NSA terms a conversation that is captured, decoded
if necessary, and distributed to the requesting agency is not
considered  to be the product of eavesdropping unless one of the
parties to the conversation is explicitly targeted. However, the
NSA does not depend on semantic defences; it can also produce
some legal arguments for exempting itself from normal
requirements.

On the rare occasions when NSA officials have to testify before
Congress, they have claimed a mandate broad enough to require a
special legal situation. In 1975, the NSA found its activities
under scrutiny by the Senate Intelligence Committee, chaired by
Frank Church; the House Select Committee on the Intelligence
Community, under Otis Pike; and the House Government Operations
Subcommittee on Government Information and Individual Rights, led
by Bella Abzug. The agency was notably consistent in responding
to those committees.

When Lt. Gen. Lew Allen appeared before the Pike committee, he
pointed out that it was the first time an NSA director had been
required to testify in open session. Two days earlier, CIA
director William Colby had testified that the NSA was not always
able to separate the calls of U.S. citizens from the traffic it
monitors. The general counsel of the NSA, Roy Banner, joined
Allen as witness. he was asked if, in his opinion, the NSA could
legally intercept overseas telephone calls from U.S. citizens
despite the legal prohibition on wiretapping. He replied, "That
is correct."

The top three officers of the NSA spoke with a single voice to
the Church committee. When the committee's chief counsel said to
Allen, "You believe you are consistent with the statutes, but
there is not any statute that prohibits your interception of
domestic communications." When deputy director Buffham was asked
about the legality of domestic aspects of the Huston plan, he
said, "Legality? That particular aspect didn't enter into the
discussions." Counsel Banner responded at least three times to
similar questions that the program had been legal at the time.
(Testimony took place on Oct. 29, 1975; Project Shamrock and its
watch lists were halted in mid-May of that year.)

The Abzug committee tried to get the story from the
communications corporations that had cooperated in Project
Shamrock. its hearings in late 1975 were unproductive because RCA
and ITT informed the committee, two days before hearings began,
that their executives would not appear without a subpoena; and a
former FBI agent who had been cooperating was forbidden by his
old employer from testifying. When the committee reconvened in
early 1976, it issued subpoenas to three FBI special agents, plus
one former agent; one NSA employee; and executives from
international arms of RCA, ITT, and Western Union. President Ford
prevented the five FBI/NSA people from testifying with a claim of
executive privilege, and the Attorney general requested that the
corporations refuse to comply with the subpoenas on the same
grounds. Their testimony in spite of that request brought Project
Shamrock to light less than a year after it was quickly
terminated.

There may have been some legal basis for the NSA claims of
extra-legal status. Despite having no statutory basis  or
charter, the NSA has considerable statutory protection: various
statutes, such as the COMINT statute, 18 U.S.C. 798; Public Law
86-36; and special provisions of the 1968 Omnibus Crime Control
and safe Streets Act, exempt it from normal scrutiny, even from
within the government. Thus the agency may be right in
interpreting the law to say that it can do anything not
specifically prohibited by the President of the National Security
Council.

NSCID No. 6, NSA's secret charter, includes this important
exemption (according to James Bamford's reconstruction):

  "The special nature of Communications Intelligence activities
  requires that they be treated in all respects as being outside
  the framework of other or general intelligence activities.
  Orders, directives, policies, or recommendations of any
  authority of the Executive branch relating to the collection
  ... of intelligence shall not be applicable to Communications
  Intelligence activities, unless specifically so stated and
  issued by competent departmental or agency authority
  represented on the [U.S. Communications Intelligence] Board.
  Other National Security Council Intelligence Directives to the
  Director of Central Intelligence and related implementing
  directives issued by the Director of Central Intelligence shall
  be construed as non-applicable to Communications Intelligence
  unless the National Security Council has made its directive
  specifically applicable to COMINT."

The unchecked ability to intercept and read communications,
including those of U.S. citizens within the country, would be
dangerous even if carefully regulated by elected officials held
to a public accounting.

When the method is available to officials whose names are often
unknown even to Congress who work for unaccountable agencies
like the NSA, it is very difficult for the intelligence
community, the defense community, and the Executive to refrain
form taking advantage of such easily obtained knowledge.

The lack of any effective oversight of the NSA makes it possible
for the agency to initiate or expand operations without
authorization from higher (or even other) authority. Periodic
meetings of members of the intelligence community do not
constitute true oversight or public control of government; and
the same is true of the provision of secret briefings to a small
number of senior members of the Congress, all chosen by the
intelligence community and sworn to secrecy.

Oversight of such extensive communications capability is
important enough; but NSA's capabilities are not necessarily
limited to intercepting and decrypting communications. The NSA
can also issue direct commands to military units involved in
Signals Intelligence (SIGINT) operations, bypassing even the
Joint Chiefs of Staff. Such orders are subject only to appeal to
the Secretary of Defense, and provide the NSA with capabilities
with which it could conceivably become involved in operations
beyond the collection of intelligence. At least, it does not seem
to be legally restrained from doing so.

It appears that the only effective restraint on the NSA is the
direct authority of the President, the National Security Council
(NSC), the Secretary of Defense, and the U.S. Intelligence Board.
Since the agency was created and chartered in secret by the
President and the NSC, it can presumably be modified in secret by
the same authorities.

Nor is the NSA bereft of means of influence other branches of
government, as Marchetti and Marks note:

   "A side effect of the NSA's programs to intercept diplomatic
   and commercial messages is that rather frequently certain
   information is acquired about American citizens, including
   members of Congress and other federal officials, which can be
   highly embarrassing to those individuals. This type of
   intercept message is handled with even greater care than the
   NSA's normal product, which itself is so highly classified a
   special security clearance is needed to see it."


Complete control over a secret agency with at least 60,000 direct
employees, a $10 billion budget, direct command of some military
units, and the ability to read all communications would be an
enormous weapon with which to maintain tyranny were it to arise.
A President with a Napoleonic or Stalinistic delusion would find
the perfect tool for the constant supervision of the individual
by the state in the NSA; not unlike scenarios depicted in novels
such as Orwell's 1984.

Senator Schweiker of the Church committee asked NSA director Allen
if it were possible to use NSA's capabilities "to monitor
domestic conversations within the United States if some person
with malintent desired to do it," and was probably not surprised
by Allen's "I suppose that such a thing is technically possible."
Certainly Senator Church feared the possibility:

   "That capability at any time could be turned around on the
   American people and no American would have any privacy left,
   such is the capability to monitor everything: telephone
   conversations, telegrams, it doesn't matter. There would be no
   place to hide. If this government ever became a tyranny, if a
   dictator ever took charge in this country, the technological
   capacity that the intelligence community has given the
   government could enable it to impose total tyranny, and there
   would be no way to fight back, because the most careful effort
   to combine together in resistance to the government, no matter
   how privately it was done, is within the reach of the
   government to know. Such is the capability of this technology
   ...

   I don't want to see this country ever go across the bridge. I
   know the capability that is there to make tyranny total in
   America, and we must see it that this agency and all agencies
   that possess this technology operate within the law and under
   proper supervision, so that we never cross over that abyss.
   That is the abyss from which there is no return..."


[This concludes part one of our two-part series on the National
Security Agency. Read part 2. "The NSA and the Clipper
Initiative," in next month's Claustrophobia.]

--------------------------------------------------------------

Charles Dupree writes user documentation for a Silicon Valley
software company. In recent years he has become concerned at the
intrusive power of the National Security Agency; but this is
probably just the effect of his antisocial habit of reading.


8<------ Snip, snip ---------

For more information on Claustrophobia, contact Dena Bruedigam at
[e-mail]

Paul Ferguson               |  "Government, even in its best state,
Network Integrator          |   is but a necessary evil; in its worst
Centreville, Virginia USA   |   state, an intolerable one."
[e-mail]             |      - Thomas Paine, Common Sense

         I love my country, but I fear its government.




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Date: Thu, 5 Aug 1993 09:38:21 -0400
From: Peter Wayner <[e-mail]>
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The Rule of Law and the Clipper Escrow Project

Last Thursday, I attended the first day of the Computer System Ssecurity
and Privacy Advisory Board in Washington. This is a group of industry
experts who discuss topics in computer security that should affect the
public and industry. Some of the members are from users like banks and
others are from service providing companies like Trusted Information
Services. Lately, their discussion has centered on the NSA/NIST's
Clipper/Capstone/Skipjack project and the effects it will have on
society.

At the last meeting, the public was invited to make comments and they
were almost unanimously skeptical and critical. They ranged from
political objections to the purely practical impediments. Some argued
that this process of requiring the government to have the key to all
conversations was a violation of the fourth amendment of the
constitution prohibiting warrentless searches. Others noted that a
software solution was much simpler and cheaper even if the chips were
going to cost a moderate $25. There were many different objections,
but practically everyone felt that a standard security system was
preferable.

This meeting was largely devoted to the rebutals from the
government. The National Security Association, the Department of
Justice, the FBI, the national association of District Attorneys
and Sheriffs and several others were all testifying today.

The board itself runs with a quasi-legal style they make a point of
making both video and audio tapes of the presentations. The entire
discussion is conducted with almost as much gravity as Congressional
hearings.  The entire meeting was suffused with an air of ernest
lawfullness that came these speakers. All of them came from the upper
ranks of the military or legal system and a person doesn't rise to
such a position without adopting the careful air of the very diligent
bureaucrat. People were fond of saying things like, "Oh, it's in the
Federal Register.  You can look it up." This is standard operating
procedure in Washington agencies and second nature to many of the
day's speakers.

Dorothy Denning was one of the first speakers and she reported on
the findings of the committee of five noted public cryptologists
who agreed to give the Clipper standard a once-over. Eleven people
were asked, but six declined for a variety of reasons. The review
was to be classified "Secret" and some balked at this condition
because they felt it would compromise their position in public.

The talk made clear that the government intended to keep the
standard secret for the sole purpose of preventing people from
making unauthorized implementations without the law enforcement
back door. Dr. Denning said that everyone at the NSA believes
that the algorithm could withstand public knowledge with no trouble.
The review by the panel revealed no reason why they shouldn't trust
this assessment.

Although lack of time lead the panel to largely rubberstamp
the more extensive review by the NSA, they did conduct a few tests
of their own. They programmed the algorithm on a Cray YMP, which
incidentally could process 89,000 encryptions per second in single
processor mode. This implementation was used for a cycling test which
they found seemed to imply that there was good randomness. The test
is done by repeatedly encrypting one value of data until a cycle occurs.
The results agreed with what a random process should generate.

They also tested the system for strength against a differential
cryptanalysis attack and found it worthy. There was really very
little other technical details in the talk. Saying more would
have divulged something about the algorithm.

My general impression is that the system is secure. Many people
have played paranoid and expressed concerns that the classified
algorithm might be hiding a trapdoor. It became clear to me that
these concerns were really silly. There is a built-in trapdoor
to be used by the government when it is "legal authorized" to
intercept messages. The NSA has rarely had trouble in the past
exercising either its explicitly granted legal authority  or
its implied authority. The phrase "national security" is a
powerful pass phrase around Washington and there is no reason
for me to believe that the NSA wouldn't get all of the access
to the escrow database that it needs to do its job. Building in
a backdoor would only leave a weakness for an opponent to exploit
and that is something that is almost as sacrilidgeous at the NSA
as just putting the classified secrets in a Fed Ex package to
Saddam Hussein.

Next there was a report from Geoff Greiveldinger , the man from the
Department of Justice with the responsibility of implementing the the
Key Escrow plan. After the Clipper/Capstone/SkipJack chips are
manufactured, they will be programmed with an individual id number and
a secret, unique key. A list is made of the id, key pairs and this
list is split into two halves by taking each unique key, k, and
finding two numbers a and b such that a+b=k. (+ represents XOR). One
new list will go to one of the escrow agencies and one will go to the
other. It will be impossible to recover the secret key without getting
the list entry from both agencies.

At this point, they include an additional precaution. Each list
will be encrypted so even the escrow agency won't be able to
know what is in its list. The key for decoding this list will
be locked away in the evesdropping box. When a wiretap is authorized,
each escrow agency will lookup the halves of the key that correspond
to the phone being tapped and send these to evesdropping box
where they will be decrypted and combined. That means that
two clerks from the escrow agencies could not combine their
knowledge. They would need access to a third key or an evesdropping
box.

It became clear that the system was not fully designed. It wasn't
obvious how spontenaeous and fully automated the system would
be. Mr. Greiveldinger says that he is trying to balance the tradeoffs
between security and efficiency. Officers are bound to be annoyed and
hampered if they can't start a tap instanteneously. The kidnapping of
a child is the prototypical example of when this would be necessary.

The courts also grant authority for "roving" wiretaps that allow
the police to intercept calls from any number of phones. A tap like
this begs out for a highly automated system for delivering the
keys.

I imagine that the system as it's designed will consist of escrow
computers with a few clerks who have nothing to do all day. When
a tap is authorized, the evesdropping box will be programmed with
a private key and shipped to the agents via overnight express. When
they figure out the id number of the phone being tapped, the evesdropping
box will probably phone the two escrow computers, perform a bit of
zero-knowledge authorization and then receive the two halves of the
key. This would allow them to switch lines and conduct roving
taps effectively. The NSA would presumably have a box that would
allow them to decrypt messages from foreign suspects.

At this point, I had just listened to an entirely logical presentation
from a perfect gentleman. We had just run though a system that had many
nice technological checks and balances in it. Subverting it seemed
very difficult. You would need access to the two escrow agencies and
an evesdropping box. Mr. Greiveldinger said that there would be many
different "auditting" records that would be kept of the taps. It was
very easy to feel rather secure about the whole system in a nice,
air-conditioned auditorium where clean, nice legally precise people
were speaking in measured tones. It was very easy to believe in
the Rule of Law.

To counteract this, I tried to figure out the easiest way for me
to subvert the system. The simplest way is to be a police officer
engaged in a stakeout of someone for whom you've already received
a warrant. You request the Clipper evesdropping box on the off chance
that the suspect will buy a Clipper phone and then you "lend" it
to a friend who needs it. I think that the automation will allow
the person who possesses the box to listen in to whatever lines
that they want. The escrow agency doesn't maintain a list of people
and id numbers-- they only know the list matching the id number to
the secret key. There is no way that they would know that a request
from the field was unreasonable. Yes, the audit trails could be
used later to reconstruct what the box was used for, but that would
only be necessary if someone got caught.

The bribe value of this box would probably be hard to determine,
but it could be very valuable. We know that the government of France
is widely suspected of using its key escrow system to evesdrop on
US manufacturers in France. Would they be willing to buy evesdropping
time here in America? It is not uncommon to see reports of industrial
espionage where the spies get millions of dollars. On the other hand,
cops on the beat in NYC have been influenced for much less. The
supply and demand theory of economics virtually guarantees that
some deals are going to be done.

It is not really clear what real effect the key escrow system is going
to have on security. Yes, theives would need to raid two different
buildings and steal two different copies of the tapes. This is
good. But it is still impossible to figure out if the requests from
the field are legitimate-- at least within the time constraints posed
by urgent cases involving terrorism and kidnapping.

The net effect of implementing the system is that the phone system
would be substantially strengthened against nieve intruders, but the
police (and those that bribe them) would still be able to evesdrop
with impunity. Everyone needs to begin to do a bit of calculus between
the costs and benefits of this approach. On one hand, not letting the
police intercept signals will let the crooks run free but on the other
hand, the crooks are not about to use Clipper phones for their secrets
if they know that they can be tapped.

The most interesting speaker was the assistant director of the National
Security Agency, Dr. Clint Brooks. He immediately admitted that the
entire Clipper project was quite unusual because the Agency was not
used to dealing with the open world. Speaking before a wide audience
was strange for him and he admitted that producing a very low cost
commercial competitive chip was also a new challenge for them.

Never-the-less, I found him to be the deepest thinker at the conference.
He readily admitted that the Clipper system isn't intended to catch
any crooks. They'll just avoid the phones. It is just going to deny
them access to the telecommunications system. They just won't be able
to go into Radio Shack and buy a secure phone that comes off the line.

It was apparent that he was somewhat skeptical of the Clipper's potential
for success. He said at one point the possibilities in the system
made it worth taking the chance that it would succeed. If it could capture
a large fraction of the market then it could help many efforts of the
law enforcement and intelligence community.

When I listened, though, I began to worry about what is going to happen
as we begin to see the eventual blurring of data and voice communications
systems. Right now, people go to Radio Shack to buy a phone. It's the
only way you can use the phone system. In the future, computers, networks
and telephones are going to be linked in much more sophisticated ways.
I think that Intel and Microsoft are already working on such a technology.

WHen this happens, programmable phones are going to emerge. People
will be able to pop a new ROM in their cellular digital phone or
install new software in their computer/video game/telephone. This
could easily be a proprietary encryption system that scrambles
everything. The traditional way of controlling technology by
controlling the capital intensive manufacturing sites will be gone. Sure,
the NSA and the police will go to Radio Shack and say "We want your
cooperation" and they'll get it. But it's the little, slippery ones
that will be trouble in the new, software world.

The end of the day was dominated by a panel of Law Enforcement specialists
from around the country. These were sheriffs, district attorneys,
FBI agents and other officers from different parts of the system.
Their message was direct and they didn't hesitate to compare encryption
with assault rifles. One even said, "I don't want to see the officers
outgunned in a technical arena."

They repeatedly stressed the incredible safe guards placed upon
the wiretapping process and described the hurdles that the officers
must go through to use the system. One DA from New Jersey said that
in his office, they process about 10,000 cases a year, but they only
do one to two wiretaps on average. It just seems like a big hassle
and expense for them.

It is common for the judges to require that the officers have very
good circumstantial evidence from informers before giving them
the warrant. This constraint coupled with the crooks natural hesitation
to use the phone meant that wiretaps weren't the world's greatest
evidence producers.

One moment of levity came when a board member asked what the criminals
favorite type of encryption was. The police refused to answer this one
and I'm not that sure if they've encountered enough cases to build a
profile.

At the end of all of the earnestness and "support-the-cop-on-the-beat",
I still began to wonder if there was much value to wiretaps at all. The
police tried to use the low numbers of wiretaps as evidence that they're not
out there abusing the system, but I kept thinking that this was mainly
caused by the high cost and relatively low utility of the technique.

It turns out that there is an easy way to check the utility of these
devices. Only 37 states allow their state and local police to use
wiretaps in investigations. One member of the panel repeated the rumor
that this is supposedly because major politicians were caught with
wiretaps. The state legislatures in these states supposedly
realized that receipients of graft and influence peddlers were the main
target of wiretaps. Evesdropping just wasn't a tool against muggers.
So they decided to protect themselves.

It would be possible to check the crime statistics from each of these
states and compare them against the evesdropping states to discover
which has a better record against crime. I would like to do this
if I can dig up the list of states that allow the technique.
I'm sure that this would prove little, but it could possibly clarify
something about this technique.

It is interesting to note that the House of Representative committee
on the Judiciary was holding hearings on abuses of the National Crime
Information Center. They came in the same week as the latest round
of Clipper hearings before the CSAB. The NCIC is a large computer
system run by the FBI to provide all the police departments with a
way to track down the past records of people. The widespread access
to the system makes it quite vulnerable to abuse.

In the hearings, the Congress heard many examples of unauthorized
access. Some were as benign as people checking out employees. The
worst was an ex-police officer who used the system to track down his
ex-girlfriend and kill her. They also heard of a woman who looked
up clients for her drug-dealing boyfriend so he could avoid the
undercover cops.

These hearings made it obvious that there were going to be problems
determining the balance of grief. For every prototypical example of
a child kidnapped to make child pornography, there is a rengade
police officer out to knock off his ex-girlfriend. On the whole, the
police may be much more trustworthy than the criminals, but we need
to ask how often a system like Clipper will aid the bad guys.


In the end, I reduced the calculus of the decision about Clipper to be
a simple tradeoff. If we allow widespread, secure encryption, will the
criminals take great advantage of this system? The secure phones won't
be useful in rapes and random street crime, but they'll be a big aid
to organized endeavors. It would empower people to protect their own
information unconditionally, but at the cost of letting the criminals
do the same.

Built-in back doors for the law enforcement community, on the other
hand, will deny the power of off-the-shelf technology to crooks,
but it would also leave everyone vulnerable to organized attacks
on people.

I began to wonder if the choice between Clipper and totally secure
encryption was moot. In either case, there would be new opportunities
for both the law-abiding and the law-ignoring. The amount of crime
in the country would be limited only by the number of people who
devote their life to the game-- not by any new fangled technology
that would shift the balance.


I did not attend the Friday meeting so someone else will need to summarize
the details.