Re: DES & IBM's patents

Bruce Schneier (schneier@counterpane.com)
Wed, 22 Jul 1998 10:58:15 -0500

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At 12:20 PM 7/20/98 -0700, Bob Baldwin wrote:
>
>On Mon, 20 Jul 1998 14:45:22-0400, Perry E. Metzger wrote:
>>DES has been routinely used in weird new modes, and IBM never
>>attempted to enforce the patent on it under any circumstances.
>>They accepted that DES was no longer something they should
>>expect to profit from.
>
>Actually, IBM has enforced its patents for digest functions
>based on DES (or any other block cipher) called MDC-2
>and MDC-4. It also has a patent on using DES to create
>a 40-bit keyspace version called CDMF. Both of these
>"weird new modes" for DES are patented and IBM does in
>fact enforce them.

Um, no. IBM has not enforced their DES patents for any
weird new modes. They have seperate patents on MDC-2 and
MDC-4. Those patents have nothingt to do with DES; they are
implementable with any block cipher.

Your statement is scarey, and will definitely come up in the
AES selection process.

Bruce
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