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Re: [quicwg/base-drafts] Optimistic ACKs and PFS in security considerations (#2160)

ekr <notifications@github.com> Thu, 13 December 2018 21:03 UTC

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Subject: Re: [quicwg/base-drafts] Optimistic ACKs and PFS in security considerations (#2160)
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```
The second mitigation is that the server can require that acknowledgments for
sent packets match the encryption level of the sent packet.  This mitigation is
useful if the connection has an ephemeral forward-secure key that is generated
and used for every new connection.  If a packet sent is protected with a
forward-secure key, then any acknowledgments that are received for them MUST
also be forward-secure protected.  Since the attacker will not have the
forward-secure key, the attacker will not be able to generate forward-secure
protected packets with ACK frames.
```

I don't understand what this means. Forward-security doesn't matter
here because you always get fresh keys for each connection and if you
don't see SH, you can't send packets.


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