Subject: DIGEST-MD5: Family of mechanisms?

From: Keith Burdis <[email-masked]>
Date: Tue, 27 Mar 2001 17:58:21 +0200 (SAST)

Hi there

One possible change to the Digest-MD5 specification could be to
make it specify a family of mechanism, each using a different
one-way function. This would mean that the same mechanism
could be used with new and existing one-way functions, and would
minimise the problems caused by a weakness being found in any
particular one-way function.

This specification would still be upwardly compatible with the
HTTP \"md5-sess\" algorithm, since Digest-MD5 would be the same as
before.

Does anyone think that such a change would be useful? What are
the potential drawbacks of this change?
 
  - Keith
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Keith Burdis                        
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From: "Kurt D. Zeilenga" <[email-masked]>
Date: Tue, 27 Mar 2001 10:33:58 -0800

>the potential drawbacks of this change?

We just need to be careful not to cause DIGEST-MD5 to unnecessarily
recycle at Proposed.

I did chat with JeffS and he thought we likely can add AES as an
alternative cipher without recycling.  We might be able to add SHA1,
or at least the framework for additional hash functions, without
recycling at Proposed.

Kurt

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From: Alexey Melnikov <[email-masked]>
Date: Wed, 28 Mar 2001 20:43:10 -0700

"Kurt D. Zeilenga" wrote:

> >Does anyone think that such a change would be useful?

I support the idea.

> What are

I believe you are right. Section 1.1 of the RFC 2831 says:

>1.1  Conventions and Notation
>
[skipped]
>   Let H(s) be the 16 octet MD5 hash [RFC 1321] of the octet string s.

This seems like an intention of the authors to be able to use different
hashing algorithms.

Alexey

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From: Lawrence Greenfield <[email-masked]>
Date: Fri, 30 Mar 2001 14:30:04 -0500

I am generally NOT in favor of this change.  As Paul points out,
DIGEST-MD5 is not fully parametric over the choice of one-way
functions (it expects certain size results, etc.).  Doing this would
contribute to a glut of different mechanisms, with the corresponding
blow ups in code or interoperability problems.

If there's a security problem with the choice of a one-way function,
we should choose a different one-way function and issue a
specification for that, and encourage people to migrate.

Larry

   Date: Tue, 27 Mar 2001 17:58:21 +0200 (SAST)
   From: Keith Burdis <[email-masked]>

   Hi there

     - Keith
   --
   Keith Burdis                        
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From: "Kurt D. Zeilenga" <[email-masked]>
Date: Tue, 27 Mar 2001 10:33:58 -0800

Kurt

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From: Alexey Melnikov <[email-masked]>
Date: Wed, 28 Mar 2001 20:43:10 -0700

I support the idea.

[skipped]

Alexey

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From: Lawrence Greenfield <[email-masked]>
Date: Fri, 30 Mar 2001 14:30:04 -0500

Larry

   Hi there

     - Keith
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   Keith Burdis                        
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