Subject: A proposal for pachecksum and hash agility

From: Sam Hartman <[email-masked]>
Date: Thu, 05 Jan 2006 17:44:47 -0500

I propose that in the next rev of pkinit, the paChecksum field become
optional.  The document should require that a particular error be
returned by current KDCs if the pachecksum field is not included.
This error should support TypedData.

Then in the future, we can add either an algorithm ID and Hash or we
can add a sequence of algorithm ID hash tuples.

New clients wishing not to use SHa-1 will send a new style message
without the paChecksum fiennnld.  an old KDC will respond with the error
required by the spec.  That will allow a new client to know that it
needs to retry with SHA-1.

New KDCs will interpret the new fields and use a newer hash.

New clients will probably want to include a non-sha-1 hash even when
including sha-1 in order to avoid downgrade attacks.

But we can work out the details of new behavior later.  The important
thing to get right now is a mechanism for not sending SHA-1 while
still being informed by an old KDC that SHA-1 is required.

--Sam

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From: Jeffrey Hutzelman <[email-masked]>
Date: Thu, 05 Jan 2006 22:20:32 -0500

> still being informed by an old KDC that SHA-1 is required.

I support this proposal.

After further evaluation, I withdraw my concern about KDF negotiation, as I 
can see an obvious means of adding KDF negotiation in the future that does 
not depend on having any form of algorithm ID today.  The language is a 
little clunky, but I don't think that's a problem.

-- Jeff

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From: Brian Tung <[email-masked]>
Date: Fri, 6 Jan 2006 09:59:05 -0800

> This error should support TypedData.

This (along with the rest, which I've snipped) sounds good to me.

-- 
Brian Tung <[email-masked]>
USC Information Sciences Institute

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From: Love Hörnquist Åstrand <[email-masked]>
Date: Thu, 12 Jan 2006 14:00:10 +0100

> This error should support TypedData.

This is all fine with me.

Love

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From: "Liqiang(Larry) Zhu" <[email-masked]>
Date: Thu, 12 Jan 2006 09:40:19 -0800

-32 was submitted with this change and this change only.

________________________________

From: [email-masked] on behalf of Love Hörnquist Åstrand
Sent: Thu 1/12/2006 5:00 AM
To: Sam Hartman
Cc: [email-masked]
Subject: Re: A proposal for pachecksum and hash agility

Love