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From Jason Smith <...@iriscouch.com>
Subject Re: Why MD5 is used for hashes, also about non-deterministic IDs.
Date Tue, 15 Nov 2011 06:33:20 GMT
On Tue, Nov 15, 2011 at 4:41 AM, Alex Besogonov
<alex.besogonov@gmail.com> wrote:
> Now I make a change to 'Doc' at machine A. This creates a new revid
> with new md5 hash.
> A malicious software somehow learns about this update and creates
> another document
> on machine B, contriving it so to make the resulting hash to be the
> same as on machine A.

Before going any further, you must show why we care about the contents
of machine B.

Why would I log in to machine B if I do not trust B's owner? Why would
I clone your Git repository if I do not know you?

Finally, revision tokens might look like MD5, but they are not. They
especially look like MD5 if you read the source code. But they are not
MD5. They are opaque tokens. They do not serve a security function.
Between trusted nodes, they indicate document changes.

rsync used MD4 because it was faster, and who cares? You have already
authenticated (SSH) and been authorized (permission bits).

-- 
Iris Couch

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