Re: Any truth to rumor that NSA had Public Key Crypto first?

From: David Wagner (daw_at_taverner.cs.berkeley.edu)
Date: 09/28/04 

Date: Tue, 28 Sep 2004 06:48:34 +0000 (UTC)

Roger Schlafly wrote:
>"George Ou" <533george_ou234@netzero234.com> wrote
>> According to Bruce, the NSA may have been 20 years ahead of the
>> academic community in 1970.
>
>He says:
>It took the academic community two decades to figure out that the NSA
>"tweaks" actually improved the security of DES. This means that back in the
>'70s, the National Security Agency was two decades ahead of the state of the
>art.
>
>But I don't think that's true. I believe that the advantages of
>DES over Lucifer were known much earlier.

I presume he's referring to differential cryptanalysis, which explained
an awful lot about the design of DES and which (supposedly) demonstrates
that the changes made to DES actually improved its security. Those principles
were not openly known in the 70s.

See, e.g., Coppersmith's paper "The Data Encryption Standard (DES) and
its strength against attacks", where he states that many of the principles
of differential cryptanalysis were known (under the name "T attack", T
referring to "tickling" the cipher with a small changes to the plaintext)
to the IBM team that designed DES in the 1970's, but the team did not
publish its knowledge for fear of adverse consequences to national security.
The paper seems quite credible to me.

Relevant Pages

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