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Subject: Re: q&d comparison (was Re: [Cryptix-Users] Rijndael - the real work now begins)
From: Andi Kleen (akmuc.de)
Date: Mon Oct 09 2000 - 07:53:12 CDT

On Mon, Oct 09, 2000 at 12:33:39AM +0200, Paulo S. L. M. Barreto wrote:
> On Sun, 08 Oct 2000, Ben Laurie wrote:
> > Ian Grigg wrote:
> > > On the amount of entropy, well, I'd leave that to a cryptographer,
> > > other than the observation that Rijndael has 128, 192, 256 bit keys,
> > > whilst DES has 56 bits and T-DES has 168 (full).
> >
> > Nnng. I know you know this, but the triple DES key is only worth 112
> > bits. Which is why there is no double DES.
>
> And DES is only worth 43 bits due to linear attacks (hence by today's standards
> I'd say DES is a broken cipher, irrespective of the short key size).

My understanding was that the linear attack on DES requires 2^43 chosen
plaintexts, which makes it irrelevant in practice. I am wrong ?

-Andi