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Re: problems with SHA-1

> IBM developed a cypher called "lucifer".  The NSA examined it,
> recommended some changes to the algorithm, and the result was DES.

Changes which, we now know, *strengthened* it against differential
cryptanalysis (which they new about in the 70's, and called the
"sliding attack", if I remember Copperfield's comments correctly...)

> (Why did they approve it??  They *break* codes)

That's only one of their jobs. They're *also* in charge of *providing*
communications security to the government.

> Also, DES is not approved by the government for internal use if the
> security level is Top Secret or above (if memory serves correctly).

Nope; it's actually not approved for *any* classification level.  NSA
supplies special tools and keying material for classified data
handling.  DES was for *commercial* and *personal* data...

> Strange that the government recommends that businesses use a cypher they
> don't use, don't you think?

Nope; as far as is publically known, for classified material they only
ever approved *hardware* solutions. (In the original DES spec, a
"correct" implementation had to be in hardware; certification of
software implementations came maybe 10 years later...) Of course, we
only know this after 20+ years of scrutiny and analysis, and that
doesn't help us judge the *current* political situation.

Also note that although SHA predated the MD5 attack mentioned here,
didn't SHA-1 (with a change from a shift to a rotate in one place, or
something subtle like that) come later?

DES is way past it's prime, which is why 3DES, though computationally
expensive, is a convincing followon partly *because* it takes
advantage of the extensive history of DES.  (3DES, like DES, still
only gives you a 64bit hash, though, so it doesn't compete with

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