Re: DES & IBM's patents

Perry E. Metzger (perry@piermont.com)
Mon, 20 Jul 1998 15:54:54 -0400

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Bob Baldwin writes:
> 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.

Those are not the original DES patent, however -- they are different
later patents. They have never tried to enforce the original patent in
any way. For example, Kerberos IV uses DES in a weird mode -- but IBM
has never taken any action.

> 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.
>
> --Bob Baldwin
> RSA Data Security
>
>
>

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