Re: [TLS] Certificate compression draft
Rob Stradling <rob.stradling@comodo.com> Thu, 09 March 2017 11:55 UTC
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To: Hannes Tschofenig <hannes.tschofenig@gmx.net>
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From: Rob Stradling <rob.stradling@comodo.com>
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Date: Thu, 09 Mar 2017 11:55:43 +0000
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Subject: Re: [TLS] Certificate compression draft
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Hi Hannes. Cached-Info is useful, but it can only "compress" if the client has previously seen and cached the server's certificate. AIUI, the purpose of draft-ghedini-tls-certificate-compression is to enable compression even in cases where the client hasn't yet seen the server's certificate. On 07/03/17 08:14, Hannes Tschofenig wrote: > Hi Victor > > why don't you use RFC 7924: > https://tools.ietf.org/html/rfc7924 > > This provides an even better "compression" ratio. > > Ciao > Hannes > > > On 03/06/2017 11:58 PM, Victor Vasiliev wrote: >> Certificate compression has been discussed on this list briefly before, and >> there was some interest in at least considering a draft for it. The >> draft now >> exists (co-authored by Alessandro and myself), and it can be found at: >> >> https://datatracker.ietf.org/doc/draft-ghedini-tls-certificate-compression/ >> [ GitHub repo: https://github.com/ghedo/tls-certificate-compression ] >> >> The proposed scheme allows a client and a server to negotiate a compression >> algorithm for the server certificate message. The scheme is purely >> opt-in on >> both sides. The current version of the draft defines zlib and Brotli >> compression, both of which are well-specified formats with an existing >> deployment experience. >> >> There are multiple motivations to compress certificates. The first one >> is that >> the smaller they are, the faster they arrive (both due to the transfer >> time and >> a decreased chance of packet loss). >> >> The second, and more interesting one, is that having small certificates is >> important for QUIC in order to achieve 1-RTT handshakes while limiting the >> opportunities for amplification attacks. Currently, TLS 1.3 over TCP >> without >> client auth looks like this: >> >> Round trip 1: client sends SYN, server sends SYN ACK >> Here, the server provides its own random value which client will >> have to echo in the future. >> Round trip 2: client sends ACK, ClientHello, server sends >> ServerHello...Finished >> Here, ACK confirms to server that the client can receive packets and >> is not >> just spoofing its source address. Server can send the entire >> ServerHello to >> Finished flight. >> >> In QUIC, we are trying to merge those two rounds into one. The problem, >> however, is that the ClientHello is one packet, and >> ServerHello...Finished can >> span multiple packets, meaning that this could be used as an amplification >> attack vector since the client's address is not yet authenticated at >> this point. >> In order to address this, the server has to limit the number of packets >> it sends >> during the first flight (i.e. ServerHello...Finished flight). Since >> certificates make up the majority of data in that flight, making them >> smaller >> can push them under the limit and save a round-trip. >> >> Cheers, >> Victor. -- Rob Stradling Senior Research & Development Scientist COMODO - Creating Trust Online
- [TLS] Certificate compression draft Victor Vasiliev
- Re: [TLS] Certificate compression draft Martin Thomson
- Re: [TLS] Certificate compression draft Victor Vasiliev
- Re: [TLS] Certificate compression draft Viktor Dukhovni
- Re: [TLS] Certificate compression draft Vlad Krasnov
- Re: [TLS] Certificate compression draft Victor Vasiliev
- Re: [TLS] Certificate compression draft Victor Vasiliev
- Re: [TLS] Certificate compression draft Martin Thomson
- Re: [TLS] Certificate compression draft Vlad Krasnov
- Re: [TLS] Certificate compression draft Ryan Sleevi
- Re: [TLS] Certificate compression draft Viktor Dukhovni
- Re: [TLS] Certificate compression draft Martin Thomson
- Re: [TLS] Certificate compression draft Hannes Tschofenig
- Re: [TLS] Certificate compression draft Rob Stradling
- Re: [TLS] Certificate compression draft Eric Rescorla
- Re: [TLS] Certificate compression draft Victor Vasiliev
- Re: [TLS] Certificate compression draft Sankalp Bagaria
- Re: [TLS] Certificate compression draft Ryan Sleevi
- Re: [TLS] Certificate compression draft Eric Rescorla
- Re: [TLS] Certificate compression draft Benjamin Kaduk
- Re: [TLS] Certificate compression draft David Benjamin
- Re: [TLS] Certificate compression draft Eric Rescorla
- Re: [TLS] Certificate compression draft Eric Rescorla
- Re: [TLS] Certificate compression draft Sankalp Bagaria