Re: [tcpinc] Resumption safety (was "Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpcrypt-09: (with DISCUSS and COMMENT)")

"Valery Smyslov" <> Tue, 12 December 2017 20:05 UTC

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From: "Valery Smyslov" <>
To: "Tero Kivinen" <>, "Valery Smyslov" <>
Cc: "'Eric Rescorla'" <>, "'Kyle Rose'" <>, "'Mirja Kuehlewind \(IETF\)'" <>, "'tcpinc'" <>, "'Black, David'" <>
References: <> <> <> <01bc01d36a71$45957db0$d0c07910$> <> <B0FB25D40E23475C9259A4C204B327D2@chichi> <> <> <> <073801d37315$90c89bd0$b259d370$> <> <E7AF7C0A2811484F8C475C00F74FC97D@chichi> <>
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Date: Tue, 12 Dec 2017 23:05:35 +0300
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Subject: Re: [tcpinc] Resumption safety (was "Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpcrypt-09: (with DISCUSS and COMMENT)")
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>> my point was: if VM systems are designed in such a way, that they can
>> force the inside software to reset existing cipher states in case of VM resumption
>> IN ALL cases, then we are on the safe side. Your examples below bring
>> me to a conclusion, that IN SOME (or even in most) cases these tricks work.
>> Still not sure they work always.
> Yep. They do not work always, but if we design tcpinc in same way than
> TLS, i.e., resumption always guarantees that we have new keying
> material, then solutions which work for TLS (i.e. forces TCP sessions
> to be reset, and new TCP connections to be created) will work for
> tcpinc too.

I agree that tcpinc resumption could (should?) have been designed better.
No disagreement here.

My point was more generic. If internal cipher state of any protocol
using counter mode has a chance to survive VM resumption 
and continue to work (even for a short time), then a counter re-use 
(and thus a catastrophic lose of security) could happen.
Nonce-misuse resistant modes (like GCM-SIV) would help in this case.