Re: [tcpm] Review of draft-ietf-tcpm-tcp-auth-opt-01

"Adam Langley" <agl@imperialviolet.org> Mon, 28 July 2008 16:48 UTC

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Date: Mon, 28 Jul 2008 09:48:11 -0700
From: Adam Langley <agl@imperialviolet.org>
To: Eric Rescorla <ekr@networkresonance.com>
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Subject: Re: [tcpm] Review of draft-ietf-tcpm-tcp-auth-opt-01
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On Mon, Jul 28, 2008 at 9:42 AM, Eric Rescorla <ekr@networkresonance.com> wrote:
> It depends what you mean by rekeying. If it involves a new protocol
> exchange it is incredibly painful. If you mean just running the kdf
> again, I agree that's fine.

It would just be rerunning the KDF every 2**31 bytes. I'd suggest
something along the lines of this:

For keys k1, k2, k3, ... and a manually configured master key K:

H(x) is some hash function (say SHA1)
H2(x) = H(x | "\x00")

k1 = H2(K)
k2 = H2(H(K))
k3 = H2(H(H(k)))
...


AGL


-- 
Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
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