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From: john@frog.UUCP (John Woods, Software)
Newsgroups: sci.crypt
Subject: Re: VC2000 "Update"
Message-ID: <1207@frog.UUCP>
Date: Tue, 23-Dec-86 21:42:00 EST
Article-I.D.: frog.1207
Posted: Tue Dec 23 21:42:00 1986
Date-Received: Wed, 24-Dec-86 06:45:46 EST
References: <3806@utcsri.UUCP>
Organization: Superfrog Heaven [ CRDS, Framingham MA ]
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Two comments on all this:

> From the January 1987 issue of >Home Satellite TV<, "A "CHIP" That Unlocks
> Scrambling" by Bob Cooper, Jr. (pp. 51-55, 67):
> 	"The Videocipher has been broken through the U30 device
> 	found inside of the M/A Com descrambler and pictured on
> 	our front cover.  It holds the key to a "quick decoding"
> 	fix discovered by many Videocipher hackers.  The chip is
> 	re-programmed with user instructions which essentially
> 	unlock the descrambler for transmissions which were
> 	previously secure."
> 
>The basic question still remains: Did they break DES or short-cut the keying?

I am told that they keys are transmitted encrypted with keys that are shorter
than 56 bits (i.e., some of the bits are constant), such that cracking by
exhaustive search is practical.

> the author doesn't know encryption or the law very well.  At one point he
> quotes an otherwise unreferenced announcement by NSA:
> 	"Effective 1 January 1986 ... the U.S. government will no longer
> 	sanction the DES code for encryption systems.  The DES code has
> 	become vulnerable to code breakers."
> Uhh, somehow I don't think that's quite their style...
> 
That doesn't sound like the NSA either, but I know they've said the
beaurocratic equivalent.  Some time ago, Shamir (I think) demonstrated that
DES was untrustworthy by concocting a similar encryption scheme, showing it
to people who examined it and decided that it was as secure as DES itself --
then he showed them the trapdoor hidden in the tables.  Thus, the belief that
DES _can_ have no trapdoor is undermined.

--
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA

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