Compare-by-hash

[Bob Jonkman]

Going back to a previous thread (which message-ID I have lost, and so
the continuity of the thread; sorry for the disjoint reply)


Joshua Rozen points[1] me to an article[2] on hash collisions by Valerie
Henson of Sun Microsystems:

> Recent[3] research has produced a new and perhaps dangerous technique
> for uniquely identifying blocks that I will call compare-by-hash.
> Using this technique, we decide whether two blocks are identical to
> each other by comparing their hash values, using a
> collision-resistant hash such as SHA-1. If the hash values match,
> we assume the blocks are identical without further ado. Users of
> compare-by-hash argue that this assumption is warranted because the
> chance of a hash collision between any two randomly generated blocks
> is estimated to be many orders of magnitude smaller than the chance
> of many kinds of hardware errors. Further analysis shows that this
> approach is not as risk-free as it seems at first glance.

--Bob.

[1] http://status.hackerposse.com/notice/51218
[2] http://valerieaurora.org/review/hash/node1.html
[3] "Recent" relative to 2003, when the article was published

-- 

Bob Jonkman <bjonkman-w5ExpX8uLjYAvxtiuMwx3w at public.gmane.org>         http://sobac.com/sobac/
SOBAC Microcomputer Services              Phone: +1-519-669-0388
6 James Street, Elmira ON Canada  N3B 1L5  Cell: +1-519-635-9413
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