Re: MD5 and SHA-0 collisions

From: David Wagner (daw_at_taverner.cs.berkeley.edu)
Date: 09/04/04 

Date: Sat, 4 Sep 2004 19:06:16 +0000 (UTC)

Paul Rubin wrote:
>The point is that HMAC's are used for more things than simply
>authenticating that you have the secret key.

Are they? Can you give any examples?

>The user may expect that
>if two files have the same HMAC, then they are the same file, just as
>with unkeyed MD5.

The user shouldn't expect that, particularly not if they are using
MD5-HMAC. If the user is counting on HMAC to be collision-free even
when the attacker is choosing the key, the user is doing something
funny.

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