Re: [TLS] 0RTT?
Watson Ladd <watsonbladd@gmail.com> Sun, 03 August 2014 17:32 UTC
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Date: Sun, 03 Aug 2014 10:32:30 -0700
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From: Watson Ladd <watsonbladd@gmail.com>
To: Karthikeyan Bhargavan <karthik.bhargavan@gmail.com>
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Subject: Re: [TLS] 0RTT?
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On Sun, Aug 3, 2014 at 10:25 AM, Karthikeyan Bhargavan <karthik.bhargavan@gmail.com> wrote: > >> The PMS that gets used is PMS_interim= HMAC(old_PMS, nonce || refresh >> key): data encrypted as usual under the old ciphersuite follows. > > I guess I don’t understand what this means. Is the new application data encrypted > under (a) the old MS? (b) a new MS derived from PMS_interim (and the old randoms)? I was thinking new MS. > > >> >> On receiving this a server looks up the anti-replay nonce and checks >> it is fresh. To make this easier we include UTC time since the epoch ( >> midnight of 1 January 1970) and mandate some degree of synchronization >> and a window. To avoid tagging with clock drift we truncate some low >> order bits after adding a random small offset. >> >> If the nonce is not previously seem the server can send Application >> Data as normal. >> >> We now introduce a new handshake type: Rekey Finish, containing a new >> ticket and server key. CCS follows afterwards. These are sent >> encrypted. >> >> The new PMS will be HMAC(PMS_interim, ECDH(server, client keys)). >> >> The big limitation is ticket keys are going to need rotation. This >> also doesn't address the desire to put extra data in DNS to give some >> degree of forward secrecy, but I don't think you can change DNS that >> quickly without some problems. >> >> Furthermore, if we want rekeys without renegotiation, we can reuse >> Rekey Finish and add a Rekey Initiate handshake type that will send >> the client key. >> >> Open questions: how secure is this? We certainly need to hash the >> anti-replay nonce into the keys: is that all we need? (Not if we want >> to avoid attackers manipulating which method we use) Does noisy >> truncation work to prevent fingerprinting while reducing storage >> requirements? >> >> Sincerely, >> Watson Ladd >> >> _______________________________________________ >> TLS mailing list >> TLS@ietf.org >> https://www.ietf.org/mailman/listinfo/tls > -- "Those who would give up Essential Liberty to purchase a little Temporary Safety deserve neither Liberty nor Safety." -- Benjamin Franklin
- [TLS] 0RTT? Watson Ladd
- Re: [TLS] 0RTT? Karthikeyan Bhargavan
- Re: [TLS] 0RTT? Watson Ladd
- Re: [TLS] 0RTT? Martin Thomson
- Re: [TLS] 0RTT? Watson Ladd
- Re: [TLS] 0RTT? Eric Rescorla
- Re: [TLS] 0RTT? Eric Rescorla
- Re: [TLS] 0RTT? Martin Thomson
- Re: [TLS] 0RTT? Martin Rex
- Re: [TLS] 0RTT? Watson Ladd
- Re: [TLS] 0RTT? Martin Rex