Re: [quicwg/base-drafts] Clarify that unlinkability is required for NEW_TOKEN tokens. Changes … (#2647)

Martin Thomson <> Wed, 24 April 2019 06:40 UTC

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Subject: =?UTF-8?Q?Re:_[quicwg/base-drafts]_Clarify_that_unlinkability_is?= =?UTF-8?Q?_required_for_NEW=5FTOKEN_tokens._Changes_=E2=80=A6_=28#2647=29?=
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martinthomson commented on this pull request.

>  A token SHOULD be constructed for the server to easily distinguish it from
 tokens that are sent in Retry packets as they are carried in the same field.
+The token SHOULD NOT expose linkability; i.e., information that lets observers
+correlate the connection that is using the token and the one that issued the
+Unlike the token that is created for a Retry packet, there might be some time
+between when the token is created and when the token is subsequently used.
+Thus, a token SHOULD have an expiration time, which could be either an explicit
+expiration time or an issued timestamp that can be used to dynamically calculate
+the expiration time.  A server can retain the expiration time in the server-side
+store, or embed the encrypted value in the token.  It is unlikely that the
+client port number is the same on two different connections; validating the port
+is therefore unlikely to be successful.

Yes, but the point is that you can't generally rely on it being the same between two connections.  I'm sure that those in those special circumstances will know to ignore this.

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