HaCKeRz Kr0nlcKLeZ 1/HaCKeRz Kr0nlcKLeZ.iso/chibacity/macpgp23.cpt/MacPGP2.3.rsrc/STR#_207.txt

Text File | 1993-07-02 | 13.7 KB | 573 lines




xThe Key Menu



Since the time of Julius Caesar, key management has always been the

hardest part of cryptography.  One of the principal distinguishing features

of PGP and this Macintosh adaptation is its sophisticated key management

features.







ΓÇó Generate key...



Use this command to generate your own unique public/secret key pair of a

specified size.  MacPGP shows you a menu of recommended key sizes

(casual grade, commercial grade, or military grade) and prompts you for

what size key you want, up to around a thousand bits.  The bigger the key,

the more security you get, but you pay a price in speed.





PGP also asks for a user ID, which means your name.  It's a good idea to

use your full name as your user ID, because then there is less risk of

other people using the wrong public key to encrypt messages to you.

Spaces and punctuation are allowed in the user ID.  It would help if you put

your E-mail address in <angle brackets> after your name, like so:



    Robert M. Smith <[e-mail]>



If you don't have an E-mail address, use your phone number or some other

unique information that would help ensure that your user ID is unique.



PGP also asks for a ΓÇ£pass phraseΓÇ¥ to protect your secret key in case it

falls into the wrong hands.  Nobody can use your secret key file without

this pass phrase.  The pass phrase is like a password, except that it can

be a whole phrase or sentence with many words, spaces, punctuation, or

anything else you want in it.  Don't lose this pass phraseΓÇöthere's no way

to recover it if you do lose it.  This pass phrase will be needed later

every time you use your secret key.  The pass phrase is case-sensitive,

and should not be too short or easy to guess.  It is never displayed on the

screen.  Don't leave it written down anywhere where someone else can

see it, and don't store it on your computer.  If you don't want a pass

phrase (You fool!), just press return (or enter) at the pass phrase

prompt.



The public/secret key pair is derived from the RSA process and large

random numbers generated from measuring the intervals between your

keystrokes with a fast timer.  Note that RSA key generation is a VERY

lengthy process.



The generated key pair will be placed on your public and secret key rings.

You can later use the ΓÇ£ExtractΓÇ¥ command option to extract (copy) your

new public key from your public key ring and place it in a separate public

key file suitable for distribution to your friends.  The public key file can

be sent to your friends for inclusion in their public key rings.  Naturally,

you keep your secret key file to yourself, and you should include it on

your secret key ring.  Each secret key on a key ring is individually

protected with its own pass phrase.



Never give your secret key to anyone else.  For the same reason, don't

make key pairs for your friends.  Everyone should make their own key

pair.  Always keep physical control of your secret key, and don't risk

exposing it by storing it on a remote timesharing computer.  Keep it on

your own personal computer.



Make sure you donΓÇÖt lose your unique public and private key pair to faulty

storage media or carelessnessΓÇömake backups!  If you lose your key you

will cause inconvenience to everyone who holds that public key half of the

pair, who have to communicate with you and replace it with your new one.

Also, whenever this happens, it weakens the security of the ΓÇÿtrust webΓÇÖ

in that people are being asked to make key modifications on faith and not

from the existence of a secure ΓÇ£revocation certificatesΓÇ¥.





ΓÇó Add keys...



Use this command to add a public or secret key file's contents to your

public or secret key ring (note that [brackets] denote an optional field).  A

key file may contain multiple keys.





The optional keyring file name defaults to ΓÇ£pubring.pgpΓÇ¥ or

ΓÇ£secring.pgpΓÇ¥, depending on whether the keyfile contains a public or a

secret key.  You may specify a different key ring file name under the

ΓÇ£OptionsΓÇ¥ menu.



If the key is already on your key ring, PGP will not add it again.  All of the

keys in the keyfile are added to the keyring, except for duplicates.  If the

key being added has attached signatures certifying it, the signatures are

added with the key.  If the key is already on your key ring, PGP just

merges in any new certifying signatures for that key that you don't

already have on your key ring.





ΓÇó View keyring...



Use this command to view the contents of your public key ring.  This lists

any keys in the key ring that match the specified user ID substring.  If you

omit the user ID, all of the keys in the key ring are listed.  The optional

keyring file name is assumed to be ΓÇ£pubring.pgpΓÇ¥.  It can be omitted, or

you can specify ΓÇ£secring.pgpΓÇ¥ if you want to list secret keys.  If you

want to specify a different key ring file name, you can.



To see all the certifying signatures attached to each key, use the

ΓÇ£verboseΓÇ¥ flag under the Options menu.







ΓÇó Check signatures...



To have MacPGP perform a full analysis of your public key ring, use the

key ring check command.  Associated with the keys in a keyring are

signatures of introducers attesting to authenticity, from which trust

parameters and validity scores associated with keys are derived.



Normally, PGP automatically checks any new keys or signatures on your

public key ring and updates all the trust parameters and validity scores.

In theory, it keeps all the key validity status information up to date as

material is added to or deleted from your public key ring.  But perhaps

you may want to explicitly force PGP to perform a comprehensive

analysis of your public key ring, checking all the certifying signatures,

checking the trust parameters, updating all the validity scores, and

checking your own ultimately-trusted key against a backup copy on a

write-protected floppy disk.  It may be a good idea to do this hygienic

maintenance periodically to make sure nothing is wrong with your public

key ring.





Since your own trusted public key is used as a final authority to directly

or indirectly certify all the other keys on your key ring, it is the most

important key to protect from tampering.  To detect any tampering of

your own ultimately-trusted public key, PGP can be set up to

automatically compare your public key against a backup copy on

write-protected media.



For further details, see the sections ΓÇ£How to Protect Public Keys from

TamperingΓÇ¥ and ΓÇ£How Does PGP Keep Track of Which Keys are Valid?ΓÇ¥ in

the Essential Topics volume.





ΓÇó Extract Key...



Use this command to extract (copy) a key from your public or secret key

ring.  This non-destructively copies the key specified by the user ID from

your public or secret key ring to the specified key file.  This is the

approach used to give a copy of your public key to someone else.



If the key has any certifying signatures attached to it on your key ring,

they are copied off along with the key.





If you want the extracted key represented in printable ASCII characters

suitable for email purposes, use the ΓÇ£ASCII OutputΓÇ¥ flag under the

Options menu.





ΓÇó Certify Key



Use this command to certify someone elseΓÇÖs key in your keyring as

genuine.  A file ΓÇÿcertificateΓÇÖ is created holding their public key signed by

you to attest its authenticity.  You serve as the intermediate trusted

ΓÇÿintroducerΓÇÖ for that key to others by passing them the certificate.





If you are asked to sign someone else's public key certificate, make

certain that it really belongs to that person named in the user ID of that

public key certificate.  This is because your signature on her public key

certificate is a promise by you that this public key really belongs to her.

Other people who trust you will accept her public key because it bears

your signature.  It may be ill-advised to rely on hearsay-- don't sign her

public key unless you have independent firsthand knowledge that it really

belongs to her.  Preferably, you should sign it only if you got it directly

from her.



In order to sign a public key, you must be far more certain of that key's

ownership than if you merely want to use that key to encrypt a message.

To be convinced of a key's validity enough to use it, certifying signatures

from trusted introducers should suffice.  But to sign a key yourself, you

should require your own independent firsthand knowledge of who owns

that key.  Perhaps you could call the key's owner on the phone and read

the key file to her to get her to confirm that the key you have really is

her keyΓÇöand make sure you really are talking to the right person.  See the

ΓÇ£Fingerprint keyΓÇ¥ command and the section ΓÇ£Verifying a Public Key Over

the PhoneΓÇ¥ in the Special Topics volume for further details.



Bear in mind that your signature on a public key certificate does not vouch

for the integrity of that person, but only vouches for the integrity (the

ownership) of that person's public key.  You aren't risking your credibility

by signing the public key of a sociopath, if you were completely confident

that the key really belonged to him.  Other people would accept that key as

belonging to him because you signed it (assuming they trust you), but they

wouldn't trust that key's owner.  Trusting a key is not the same as

trusting the key's owner.



For further details, see the sections ΓÇ£How to Protect Public Keys from

TamperingΓÇ¥ and ΓÇ£How Does PGP Keep Track of Which Keys are Valid?ΓÇ¥ in

the Essential Topics volume.





ΓÇó Edit Key...



Use this command to change the trust parameters associated with

someone elseΓÇÖs key, to edit your userid on your public key, or to change

the pass phrase for your secret key.





Sometimes you may need to change your pass phrase, perhaps because

someone looked over your shoulder while you typed it in.  Or you may

need to change your user ID, because you got married and changed your

name, or maybe you changed your E-mail address.  Or maybe you want to

add a second or third user ID to your key, because you may be known by

more than one name or E-mail address or job title.  PGP lets you attach

more than one user ID to your key, any one of which may be used to look

up your key on the key ring.



Sometimes you need to alter the trust parameters for a public key on

your public key ring.  For a discussion on what these trust parameters

mean, see the section ΓÇ£How Does PGP Keep Track of Which Keys are

Valid?ΓÇ¥ in the Essential Topics volume of the PGP User's Guide.  In short,

the trust parameters are a method of judging the authenticity of the keys.

If you received the key for a person via a third party, you are susceptible

to a ΓÇ£spoofingΓÇ¥ attack whereby the intermediary supplies a false key.

Complex systems and structures have been proposed for ΓÇ£certifying

authorities and hierarchiesΓÇ¥ but PGP simply lets the user choose their

own scheme.  Phil Zimmerman writes under ΓÇ£How to Protect Public Keys

from TamperingΓÇ¥ in the Special Topics volume:



ΓÇ£For more decentralized grassroots ΓÇÿguerrilla styleΓÇÖ environments,

allowing all users to act as a trusted introducers for their friends would

probably work better than a centralized key server.  PGP tends to

emphasize this organic decentralized non-institutional approach.  It better

reflects the natural way humans interact on a personal social level, and

allows people to better choose who they can trust for key management.ΓÇ¥





ΓÇó Remove Key...



Use this command to remove a key or a user ID from your public key ring.

PGP searches for the specified user ID in your key ring, and removes it if

it finds a match.  Remember that any fragment of the user ID will suffice

for a match.  The optional keyring file name is assumed to be literally

ΓÇ£pubring.pgpΓÇ¥.  It can be omitted, or you can specify ΓÇ£secring.pgpΓÇ¥ if

you want to remove a secret key.  You may specify a different key ring

file name.



If more than one user ID exists for this key, you will be asked if you want

to remove only the user ID you specified, while leaving the key and its

other user IDs intact.







ΓÇó Remove signatures...



Use this command to remove the signatures associated with a given key.

You can use this to indicate that a signature is no longer considered

trustworthy so that PGP will update trust values for affected keys

accordingly.







ΓÇó Disable/enable key...



This command can be used to temporarily enable or disable keys in a

keyfile.  This is useful to indicate that the trust of the key is not

completely lost (in which case it should be removed) but ΓÇ£on holdΓÇ¥.







ΓÇó Fingerprint key...



This command will display the key with the 16-byte digest of the public

key components.  Read this 16-byte fingerprint to the key's owner on the

phone, while she checks it against her own, using the same  command at

her end.  You can both verify each other's keys this way, and then you can

sign each other's keys with confidence.  This is a safe and convenient way

to get the key trust network started for your circle of friends.





If you get a public key from someone that is not certified by anyone you

trust, how can you tell if it's really their key?  The best way to verify an

uncertified key is to verify it over some independent channel other than

the one you received the key through.  One convenient way to tell, if you

know this person and would recognize them on the phone, is to call them

and verify their key over the telephone.  Rather than reading their whole

tiresome (ASCII-armored) key to them over the phone, you can just read

their key's ΓÇ£fingerprintΓÇ¥ to them.