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

Martin Thomson <notifications@github.com> Wed, 24 April 2019 03:18 UTC

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martinthomson commented on this pull request.

This is definitely the right sentiment, but I have a few editorial suggestions.

>  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

This is worth making a new paragraph for.  How about:

"The token MUST NOT include information that would allow it to be linked to the connection on which it was issued by an on-path observer.  For example, it cannot include the connection ID or addressing information unless the values are encrypted."

>  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
+token.
+
+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

```suggestion
the expiration time.  A server can store the expiration time or include it in an encrypted form in the token.
```

>  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
+token.
+
+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.

This sentence doesn't really flow from the previous any more.  This can probably be made into a new paragraph.

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