Re: CAST (and random AES chatter)

Bruce Schneier (schneier@counterpane.com)
Mon, 20 Jul 1998 12:56:16 -0500

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At 09:05 PM 7/20/98 +1000, Julian Assange wrote:
>"Kriston J. Rehberg" <kriston@ibm.net> writes:
>
>> I agree with Bruce; RC6 and Twofish, since they are modified and
>> extended versions of RC5 and Blowfish respectively, are based on
>> seemingly-sound algorithms that are simple enough for most of us to
>> understand at least part of them.
>>
>> Well, for me, they are.
>
>Can someone tell me what the patent situation is with RC6, given that
>RC5 is patented?

I don't know about RC6 patent applications, but one of the NIST criteria
AES must be free for everyone. LIke IBM, which gave the DES patents
to the world, RSADSI will have to do the same with any RC6 patents.

What is interesting is whether or not the RSADSI patents cover the use
of data-dependent rotations in block ciphers. IBM believes that there is
enough prior art; note the use of data-dependent rotations in MARS.

Bruce

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