Re: Call to atention about using hash functions as content indexers (SCM saga)

[Eric Rannaud <Eric.Rannaud@ens.fr>]

Simply put, the best known attack of SHA-1 takes 2^69 hash operations.
( http://www.schneier.com/blog/archives/2005/02/sha1_broken.html )
The attack is still only an unpublished paper and has not yet been
implemented. An attack is: you try as hard as you can to find a collision
between two arbitrary messages (i.e. two arbitrary --and nonsensical--
source files).
In the context of git, a better estimation would be the number of hash
operations needed to find a message that has the same hash than a given
fixed message (e.g. mm/memory.c). This is more like 2^100 hash
operations. And if a collision is found, this is very likely using a
message that *doesn't* look like a C source file...

Moreover, no example of collision is known, AFAIK.

In other words: this won't happen.

Best,
   /er.