🚀 go-pugleaf

I figured this might be worth reposting.  I'm never sure how seriously
to take much of the information I see, this being no different, but I
find it interesting none the less (they give me something to think
about as I brush my teeth).

	Mike
-------------- Start of forwarded message

Date: Fri, 25 Sep 87 09:05 EST
From: "GLENN EVERHART, 609 486 6328"
	<uw-beaver!RELAY.CS.NET!rca.com!ARISIA!EVERHART>
Subject:  Secure phones

The NSA is involved in distributing these phones as part of a more
general effort to get at least some US companies to have reliable
security.

The story I've heard (though I don't have it from classified
sources) is something like this:

1. DES was originally certified, but was designed with a short enough
key that NSA could break it by brute force. (It IS a federal law that
no cipher may be used for international traffic that NSA can't break,
so the permeability of DES follows from reading the relevant US Code
sections.) The classified algorithms are said to differ from DES mainly
in the length of their keys.

2. Recently, someone furnished NSA with an efficient DES breaking
algorithm. This was said to take 1.5 hrs. on an IBM PC to break a DES
cipher. I understand that hard details of this have been classified and
NSA does NOT particularly want to confirm this. Still, some NSA
employees have confirmed that DES is not nearly as secure as was
originally thought. Thus, NSA isn't going to certify DES again, at
least not willingly, because they KNOW it's breakable. (It's been
suggested that a different key scheduling data area could give a more
secure algorithm, but the generator for the key schedulers is not
available, at least not readily.) An Australian friend of mine
mentioned he saw an article on breaking DES back in '79 or '80 in the
Proceedings of the Soviet Academy of Sciences, but has since told me
the article deals only with certain classes of keys. (BTW, it also
mentions that if you insist on choosing large PRIMES for public key
cryptosystems keys, the public key systems become fairly easy to crack
also; what's needed are RELATIVELY PRIME numbers, not primes.)

3. Since DES has proven embarassingly easy to crack, and since large
amounts of money are "protected" by it, NSA is proposing to let
industry use the "real stuff", the algorithms they use themselves,
which hopefully are less permeable. To do so, they furnish algorithms
and keys (preserving the ability they have by law to decipher the
text), but are paying fairly large sums to develop these phones and
other boxes. A good deal of custom microelectronics is involved. And
this is why you see NSA discussing crypto phones etc. (You are of
course aware I trust that ANY phone conversation that gets onto
microwave is potentially as open to interception as home radiophones
are...and many of thesse links to industry ARE monitored...)

I've heard another story someone might comment on:
Some US company (I forget which; it's not important) sent a binary copy
of an operating system over wire to England. However they used the unix
crypt tool on it first, more than once and with different keys. The
story is they got a call a few days later from NSA demanding they give
NSA the keys used to encipher it.

The algorithm is just character XORs with a string. But if you do it
several times with strings of lengths that are relatively prime,
couldn't the effective string become the product of the key lengths,
and quickly grow comparable in size with the original message? Does
anyone out there know enough cryptography to tell me whether this is
really a super cheap and strong cipher, or whether it's just a minor
nuisance for folks who go in for this sort of thing?

Glenn
Everhart%Arisia.decnet@ge-crd.arpa
----------------- End of forwarded message
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