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Re: [TLS] 32 byte randoms in TLS1.3 hello's

Peter Gutmann <pgut001@cs.auckland.ac.nz> Tue, 25 July 2017 03:53 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Colm MacCárthaigh <colm@allcosts.net>, Stephen Farrell <stephen.farrell@cs.tcd.ie>
CC: "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] 32 byte randoms in TLS1.3 hello's
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Date: Tue, 25 Jul 2017 03:53:53 +0000
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Subject: Re: [TLS] 32 byte randoms in TLS1.3 hello's
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Colm MacCárthaigh <colm@allcosts.net> writes:

>I think the fix for this is really at the application level; if you 
>want defense-in-depth against PRNG problems, it's probably best to use 
>separate RNG instances for public data (e.g. client_random, 
>server_random, explicit_IV) and for secret data (keys) so that a leak 
>in the public data doesn't compromise the private one. We do this in 
>s2n, and I think BouncyCastle does it too. 

I do that too.  It's also specified in the LTS draft, it's just common 
sense really.

Peter.

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