SHA-1 cracked

[Steven M. Bellovin]

In message <Pine.LNX.4.44.0502161506310.23328-100000 at gilmore.ael.be>, Alexandre
 Dulaunoy writes:
>On Tue, 15 Feb 2005, Steven M. Bellovin wrote:
>
>> According to Bruce Schneier's blog 
>> (http://www.schneier.com/blog/archives/2005/02/sha1_broken.html), a 
>> team has found collisions in full SHA-1.  It's probably not a practical 
>> threat today, since it takes 2^69 operations to do it and we haven't 
>> heard claims that NSA et al. have built massively parallel hash 
>> function collision finders, but it's an impressive achievement 
>> nevertheless -- especially since it comes just a week after NIST stated 
>> that there were no successful attacks on SHA-1.
>
>and what  about HMAC-SHA1 ? Is  it reducing the  operation required by
>the same factor  or as the structure of HMAC is  so different that the
>attack is very unlikely to be practical ?
>

As the blog entry mentions, it's it's unlikely that SHA-1 is affected.

That said, the attack merits close attention; as Schneier has noted in 
other contexts, attacks always get better, never worse.

		--Prof. Steven M. Bellovin, http://www.cs.columbia.edu/~smb



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