Re: [OAUTH-WG] New Version Notification for draft-fett-oauth-dpop-03.txt

Brian Campbell <> Wed, 27 November 2019 19:19 UTC

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From: Brian Campbell <>
Date: Wed, 27 Nov 2019 12:19:24 -0700
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To: Neil Madden <>
Cc: "Richard Backman, Annabelle" <>, oauth <>
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Subject: Re: [OAUTH-WG] New Version Notification for draft-fett-oauth-dpop-03.txt
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On Wed, Nov 27, 2019 at 3:31 AM Neil Madden <>

> That is true, but is IMO more of a hindrance than an advantage for a PoP
> scheme. The very fact that the signature is valid at every RS is why you
> need additional measures to prevent cross-RS token reuse. This downside of
> signatures for authentication was pointed out by djb 18 years ago (
> which is why most modern crypto protocols either use Diffie-Hellman for
> authN ( or sign a hash of an interactive
> handshake transcript (TLS 1.3 -
> so that the signature
> is tightly bound to a specific interactive protocol run.
Mostly for my own edification -  using Diffie-Hellman for authN (that a key
was held) was effectively at the heart of the "tentative suggestion for an
alternative design" that you had much early in this thread?

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