On 2005-Feb-19 00:42:56 -0500, Anatole Shaw <shaw_bugtraq20050218@autoloop.com>
wrote:
Sadly, there is no magic bullet for the SHA-1 problem. Let me say, in
classic Bugtraq style, that I believe the "temporary workaround for this
vulnerability" is to move to SHA-512 as quickly as possible.
There are two difficulties with this. Firstly, SHA-512 generates a
hash that is somewhat over 3 times the size of SHA-1 - this may
present problems in some cases. It's definitely not going to be a
drop-in replacement.
Secondly, AFAIK, it's not yet clear that SHA-512 (or SHA-256) are
resistant to this break. Whilst a 2^11 reduction in collision resistance
would be unimportant in SHA-512, given the close relationship between the
SHA-* family, it's possible that that the _all_ of the SHA-* family have
a collision resistance similar to SHA-1 - around 2^70.
I agree that an alternative to SHA-1 is required fairly quickly. It's
less clear that SHA-512 is even a temporary work-around. I believe
that the immediate reaction would be to prepare a plan on how to
quickly replace SHA-1 with an alternative hash algorithm (probably
with a different sized result) and be ready to implement it once an
alternative is identified. If you do move to SHA-512 now, you should
probably be prepared to make another change in the near future.
The only fix will be informed analysis of the new paper from the Chinese
team (which hasn't even been released yet) and the informed development
of a solid cryptographic response.
Agreed.
--
Peter Jeremy
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