Subject: [quicwg/base-drafts] Explicitly permit starting over (#1621)

From: Martin Thomson <[email-masked]>
Date: Tue, 31 Jul 2018 17:39:48 -0700

Generating a new cryptographic handshake message is a fine response to
Retry or Version Negotiation.  It's sometimes necessary, but even when
it is not, it avoids having to worry about 0-RTT packet numbers.

Followup for #1498.
You can view, comment on, or merge this pull request online at:

  https://github.com/quicwg/base-drafts/pull/1621

-- Commit Summary --

  * Explicitly permit starting over

-- File Changes --

    M draft-ietf-quic-transport.md (9)

-- Patch Links --

https://github.com/quicwg/base-drafts/pull/1621.patch
https://github.com/quicwg/base-drafts/pull/1621.diff

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From: ekr <[email-masked]>
Date: Tue, 31 Jul 2018 19:12:54 -0700

ekr approved this pull request.

Modulo comment, LGTM

> @@ -806,7 +806,8 @@ A client MUST NOT reset the packet number it uses for 0-RTT packets.  The keys
 used to protect 0-RTT packets will not change as a result of responding to a
 Retry or Version Negotiation packet unless the client also regenerates the
 cryptographic handshake message.  Sending packets with the same packet number in
-that case would compromise the packet protection for all 0-RTT packets.
+that case could compromise the packet protection for all 0-RTT packets because

Why the change from "would" to "could". Could seems a lot more likely.

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From: Martin Thomson <[email-masked]>
Date: Tue, 31 Jul 2018 23:24:45 -0700

martinthomson commented on this pull request.

It's not guaranteed - if the exact same data is sent again, then there is no compromise.  And, from what I know of some implementations, that might even work.  But it's a long shot.  I'll tweak it to change emphasis.

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