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- From: rcain@netcom.com (Robert Cain)
- Subject: Re: Encrypted phones, keys, taps, ...
- Message-ID: <1992Nov7.045122.15675@netcom.com>
- Organization: Netcom - Online Communication Services (408 241-9760 guest)
- References: <1992Nov6.012330.4470@shearson.com>
- Date: Sat, 7 Nov 1992 04:51:22 GMT
- Lines: 45
-
- pmetzger@snark.shearson.com (Perry E. Metzger) writes:
- :
- : If "standard" means analog, well, analog phone scramblers are almost
- : all easily broken, and are pretty poor in general. Why use one when
- : digital techniques that are virtually unbreakable are available?
-
- How is this done in the case of randomly hopping variable split band
- spectrum inverters? Current technology allows hopping between any of
- 32 frequency split points at a 60 hz hopping rate. From 16.67 ms
- fragments how on earth does one gather any information as to its
- content or split point? According to Micheal Washvill a voice and
- data security specialist with a "federal agency":
-
- VSB scrambling can be broken but not in real time. The only
- practical attack is through trial and error. The scrambled
- speech must first be recorded, then divided into finite time
- segments according to the hop rate. Each segment is processed
- through a variety of split points until clear speech results."
-
- He claims a 60 to one decode time. Gimme a break! Who decides when
- clear speech results? Automatic speech recognition is nowhere near
- capable of this which leaves a human to determine what is clear
- speech. Think of the combinatorics here to decide on a second! Does
- it actually seem reasonable that this could be done in finite human
- time or is this guy blowing self serving smoke to discourage its use?
-
- Or are there more sophisticated methods? I have some experience in
- signal processing and in speech recognition and certainly can't think
- of one. I've seen the statement that it is easy but I'd sure like to
- see that backed up with an algorithm.
-
- Bob
-
- Bob
- --
- Bob Cain rcain@netcom.com 408-358-2007
-
- "One can learn to be alone, even enjoy it, but let intimacy
- break that solitude, even briefly, and one must start all
- over again."
-
- Elia Kazan
-
-
- PGP 1.0 or 2.0 public key available on request.
-