[Dshield] Crypto Question

[Valdis.Kletnieks at vt.edu]

On Wed, 04 Mar 2009 14:12:06 PST, John Hardin said:
> What's the likelihood that the same collision plaintext would generate the 
> same crypto hash using several different algorithms?

A man with one watch always knows what time it is. A man with 2 watches is
never sure.

In general, either that first hash is believed secure, or it isn't.  If it
is secure, you don't need a second hash.  If you're worried enough about the
first hash that using a second one is starting to make sense, you probably
shouldn't be using the first one at all.

Or more concretely - if you're computing a SHA-256 hash because you don't trust
the MD5 hash, maybe it's time to just *retire* the MD5 entirely.

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