From eichin at cygnus.com  Sat Jul 10 20:45:09 1993
From: eichin at cygnus.com (Mark Eichin)
Date: Sat, 10 Jul 93 20:45:09 PDT
Subject: encrypted email software
In-Reply-To: <9307110204.AA13167@buoy.watson.ibm.com>
Message-ID: <9307110345.AA10983@cygnus.com>


>> Well, first - I believe DES was designed with 64 bit keys in mind,
	and then they apparently discovered it to be sensitive to the
"sliding attack", ie. differential cryptanalysis...

>> While longer key indeed offers little protection against attacks
>> like differential cryptanalysis - it's hard to argue that it can
>> blow brute-force attack out of the water...  
	But isn't the idea differential cryptanalysis *can* blow
brute-force out of the water if the algorithm is sensitive to it, and
the symmetries that could be introduced by 64-bit DES keying might
have made it thus sensitive. It isn't just that extra key "offers
little protection", it might actually *weaken* the algorithm. (No, I'm
not an expert on DES, but I've followed the net, read the FIPS, read
Biham-Shamir, and thought about it a bit for myself.)
								_Mark_