[Melbourne-pm] Data::Token
Jacinta Richardson
jarich at perltraining.com.au
Fri May 30 04:48:51 PDT 2008
Scott Penrose wrote:
> So the question is:
>
> 1) Am I missing the threads on the net
> 2) Are we jumping to the wrong conclusion because we are mixing
> document signature faking with unpredictability
> 3) Is this really a problem and we are the first to really solve it.
I think it's 3 in so far that many of these modules were written before 17th
August 2004 (which is when Xiaoyun Wang,Dengguo Feng, Xuejia Lai, and Hongbo Yu
announced collisions for the full MD5 space (Their analytical attack was
reported to take only one hour on an IBM p690 cluster.)). Prior to this, the
general assumption seemed to be that engineering a collision would be really
hard, and finding a collision by accident would be next to impossible.
Since not everyone keeps up with cryptography news, people continue to use md5
despite its issues. This is not necessarily because it's a good idea. It may
even be as simple as when people think of hashing algorithms the first one that
comes to mind is md5.
I expect that for the purposes of generating tokens, particularly with the use
of a salt, that these issues aren't really a problem. However, if you do so you
are choosing to provide a less secure token than you could otherwise. I think
in general, using md5 for anything to do with security or with anything which
might even be vaguely connected with the idea of security, is looking like a bad
idea.
Regarding SHA1 and SHA2, "the security of SHA-1 has been somewhat compromised by
cryptography researchers. Although no attacks have yet been reported on the
SHA-2 variants, they are algorithmically similar to SHA-1 and so efforts are
underway to develop improved alternative hashing algorithms." (
http://en.wikipedia.org/wiki/SHA_hash_functions )
All the best,
J
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