[TLS] 32 byte randoms in TLS1.3 hello's
Stephen Farrell <stephen.farrell@cs.tcd.ie> Mon, 24 July 2017 15:15 UTC
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From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: [TLS] 32 byte randoms in TLS1.3 hello's
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Hiya, I'm guessing many folks interested in TLS may have been at the QUIC session in Prague and hence missed out on the excellent talk by Stephen Checkoway on the juniper dual-ec incident. (I highly recommend taking a peek at the slides [1] or reading the paper [2] or watching the video wherever that may be;-). Anyway, in TLS1.3 we've gotten rid of the gmt time option in the client and server hello, which is good, (and I do recall that discussion) but we've also changed from: // RFC5246 struct { uint32 gmt_unix_time; opaque random_bytes[28]; } Random; to: // tls1.3 -21 opaque Random[32]; Now if some TLS1.3 deployment were affected by a dual-ec attack, it'd seem like the -21 version of Random might be even better than the TLS1.2 version, for the attacker. I tried to see where that 28->32 change came from but didn't find it (apologies if I missed that). I guess it just ensures that the overall length of the struct is the same. So, a question and a possible suggestion: Q: Why do we need 32 bytes of Random? Suggestion: if we don't need that much, maybe we could change the length there, (I can see that might trigger bugs and middlebox issues) or encourage/require folks to mask out some of those bits (e.g. with zeros or some catchy hex encoded message about dual-ec:-). Cheers, S. [1] https://www.ietf.org/proceedings/99/slides/slides-99-irtfopen-anrp-stephen-checkoway-a-systematic-analysis-of-the-juniper-dual-ec-incident-00.pdf [2] https://web.eecs.utk.edu/~mschucha/netsec/readings/p468-checkoway.pdf
- [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Watson Ladd
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Ilari Liusvaara
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Russ Housley
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Peter Gutmann
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Joseph Lorenzo Hall
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Christian Huitema
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Peter Gutmann
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Christian Huitema
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Watson Ladd
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Peter Gutmann
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Martin Rex
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Jeffrey Walton
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Martin Rex
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Martin Rex
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Watson Ladd
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Eric Rescorla
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Eric Rescorla
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Ilari Liusvaara
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Salz, Rich
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Ilari Liusvaara
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Colm MacCárthaigh
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Dan Brown
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Blumenthal, Uri - 0553 - MITLL
- Re: [TLS] 32 byte randoms in TLS1.3 hello's Stephen Farrell