Subject: md5 definitely broken?

From: Tony Hansen <[email-masked]>
Date: Wed, 18 Aug 2004 14:43:33 -0400

I saw a note in the openpgp mailing list about md5 definitely being 
cracked. Anyone know more?

	Tony Hansen
	[email-masked]

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From: Simon Josefsson <[email-masked]>
Date: Wed, 18 Aug 2004 21:01:36 +0200

> cracked. Anyone know more?

"Collisions for Hash Functions MD4, MD5, HAVAL-128 and RIPEMD"
http://eprint.iacr.org/2004/199/

Whether "collisions" imply "cracked", in the real world, probably
depend on the details, and the application.  It is not clear (to me,
at least) how you would attack HMAC-MD5 based on the above result.

(FWIW, I've verified all but the RIPEMD-128 collisions in the paper.)

Regards,
Simon

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From: Russ Housley <[email-masked]>
Date: Wed, 18 Aug 2004 15:16:28 -0400

Tony:

Yes, MD5 has been broken.  A paper, "Collisions for Hash Functions MD4, 
MD5, HAVAL-128 and RIPEMD" has been posted showing collisions for MD5 and 
three other hash functions.  You can get it from:

         http://eprint.iacr.org/2004/199.pdf

It does not provide the attacks, but it does allow one to confirm the 
discovery of collisions.

The ramification of this news is pretty clear for digital signatures that 
make use of MD5, but it is less clear for other uses of MD5, like CRAM-MD5 
and HTTP Digest.

Anything that has already been signed with MD5 is definitely safe.  If one 
stops using MD5 today, nothing that has already been signed is at risk. 
However, it is getting risky to sign certificates with MD5, in my opinion.

Russ

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From: Laurence Lundblade <[email-masked]>
Date: Wed, 18 Aug 2004 13:06:24 -0700

>stops using MD5 today, nothing that has already been signed is at risk.

Except if you determine when something was signed by a signed timed stamp 
from time stamp authority that used MD5. You can't distinguish what was 
signed in the past from something that was made to look like it was signed 
in the past if you're using signed time stamps with MD5. You're OK if you 
have some *other* strong way to determine when it was signed.

LL

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From: Simon Josefsson <[email-masked]>
Date: Wed, 18 Aug 2004 21:01:36 +0200

Regards,
Simon

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From: Russ Housley <[email-masked]>
Date: Wed, 18 Aug 2004 15:16:28 -0400

Tony:

Russ

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From: Laurence Lundblade <[email-masked]>
Date: Wed, 18 Aug 2004 13:06:24 -0700

LL