Re: [RFC] adding support for md5

From: Jon Smirl <jonsmirl@gmail.com>
Date: Aug 18, 2006, 21:52 UTC
Message-ID: <9e4733910608181452x65ca937aqbfde55caa98ff6da@mail.gmail.com>
In-Reply-To: <Pine.LNX.4.63.0608172259280.25827@chino.corp.google.com>

On 8/18/06, David Rientjes <rientjes@google.com> wrote:

Show 8 quoted lines

> I'd like to solicit some comments about implementing support for md5 as a
> hash function that could be determined at runtime by the user during a
> project init-db.  md5, which I implemented as a configurable option in my
> own tree, is a 128-bit hash that is slightly more recognized than sha1.
> Likewise, it is also available in openssl/md5.h just as sha1 is available
> through a library in openssl/sha1.h.  My patch to move the hash name
> comparison was a step in this direction in isolating many of the
> particulars of hash-specific dependencies.

If I have two repositories each with 100M objects in them and I merge them, what is the probability of a object id collision with MD5 (128b) versus SHA1 (160b)?

This is not that far fetched. I know of at least four repositories with over 1M objects in them today.

-- 
Jon Smirl
jonsmirl@gmail.com