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Re: 3DES keys


"William Allen Simpson" writes:
> > From: "Perry E. Metzger" <perry@piermont.com>
> > Two n bit keys in multiple encryption schemes give you somewhat less
> > than an effective 2n key bit key length, whereas three keys actually
> > give you an effective 2n bit key length. See the discussion in
> > Schneier's book on crypto -- I think its in chapter 8.
> >
> I've read it Perry.  Hilary said this years' Crypto had a session showing
> that 2 key 3DES was no better than DES.  I'm asking for the details, or
> some refutation.

Either way I feel more comfortable with generating the extra few bytes
of keying material and going with separate keys -- in the long run we
are going to be switching to longer key lengths in new block cyphers
anyway, and its pretty clear that three keys are strictly more secure
(if only marginally so).

> And I have asked twice: what folks have implemented 3DES in hardware, so
> we can make a sensible decision on how to generate the keys?

There are a bunch of 3DES hardware implementations -- what do you need
to know specifically?

Perry
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