Re: [TLS] 0RTT?
mrex@sap.com (Martin Rex) Tue, 05 August 2014 12:34 UTC
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To: Watson Ladd <watsonbladd@gmail.com>
Date: Tue, 05 Aug 2014 14:34:13 +0200
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From: mrex@sap.com
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Subject: Re: [TLS] 0RTT?
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Watson Ladd wrote: > Martin Rex <mrex@sap.com> wrote: > > Watson Ladd wrote: > >> > >> I think I came up with a decent idea for handling 0RTT handshakes, > >> namely making resumption 0RTT, and doing a side rekeying. > > > > > > These idea(s) seem to based on a number of extremely optimistic > > assumptions that have zero chance to get airborne in many usage > > scenarios. > > > > The "regular" TLS session resumption means that client announces > > a TLS session ID in ClientHello and server looks up that session ID > > in its own cache for a match. If there is no match, a regular > > TLS full handshake proceeds. > > > > 0RTT is a no-go for a huge number of existing apps which do not > > perform any fancy reconnect fallbacks at the application level > > (closing the previous connection, opening a new connection and > > starting a new handshake from scratch while requesting different > > handshake characteristics this time). For the general case > > a 1RTT resumption is required, which can successfully perform > > a full handshake in case that resumption is not possible, > > without having to go through a connection/handshake failure. > > I think we can handle this by thinking about fallback options more > carefully. Certainly a resend can be done at the implementation level > with the new handshake: this will cost latency, but it can be done. For 0RTT this option does not exist. A multi-megabyte HTTP POST on top of a 0RTT TLS connection would waste lots of resources before even realizing that there is a problem and the bandwith was completely wasted. For other TLS extensions, a possibility to restart/reset the ongoing handshake could be defined so that TLS implementations could adopt and transparently provide it. But look at what gets pushed here in TLS WG instead: http://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00 which is a bogus proposal to panic and close the network connection on the server side and dump a genuine TLS problem entirely on the application caller of the clients TLS implementation. -Martin
- [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