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DES futile?
> From: "Perry E. Metzger" <perry@piermont.com>
> "William Allen Simpson" writes:
> > Agreed. If we change the ephemeral keys fast enough, that should be
> > good for data with time value of no more than a day or two.
>
> I disagree. See the "Big Seven" paper:
> ftp://ftp.research.att.com/dist/mab/keylength.txt
> ftp://ftp.research.att.com/dist/mab/keylength.ps
>
I've read it. In some retrospect, you are correct; it not only depends
on the time value of the data, but also the size of the attacker.
Since you are in an industry where a few million $ here and there is no
problem, you are saying that we need a _basic_ protection against large
corporations and major governments?
That is, are you saying we should abandon DES as mandatory?
> > My recommendation is to poke a stick in the sand at CAST5-128.
>
> Unfortunately, it is too new. I'd say we mandate DES as we do now, and
> recommend 3DES, which has a very solid amount of research behind
> it. CAST is probably a good idea in a couple of years when its been
> beaten up more.
>
That's why I'd poke a stick in the sand. A direction.
It sounds to me like you want something "sooner".
> > We could certainly use it for a few years until AES is defined and
> > analysed. But do we trust the AES process? Look how NBS/NIST weakened
> > DES from 112 to 56 bit keys 20 years ago! Folly!
>
> They didn't weaken it, Bill. It turns out that because of Differential
> Cryptanalysis, LUCIFER had an inherent strenth that was far lower than
> the number of keys. They only made the key length correspond to reality.
>
Mea Culpa, I went back and re-read Schneier on Lucifer, and you are
correct.
Funny how it is the "urban legend" that one remembers most clearly.
I still don't trust secret design criteria and analysis! Let's remember
that we are designing for the Internet, not the US NIST. Open, rough
consensus, running code.
WSimpson@UMich.edu
Key fingerprint = 17 40 5E 67 15 6F 31 26 DD 0D B9 9B 6A 15 2C 32
BSimpson@MorningStar.com
Key fingerprint = 2E 07 23 03 C5 62 70 D3 59 B1 4F 5E 1D C2 C1 A2
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