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Re: [TLS] chacha/poly interop?

Joachim Strömbergson <joachim@secworks.se> Fri, 16 September 2016 09:13 UTC

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From: Joachim Strömbergson <joachim@secworks.se>
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Subject: Re: [TLS] chacha/poly interop?
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Aloha!


David Benjamin wrote:
> TLS-ChaCha is actually RFC 7539 which comes with its own test
> vectors and isn't TLS-specific.
> 
> Our implementation matches RFC 7539 and seems to match the one test 
> vector I tried too. Note that that draft includes a number of things 
> like 128-bit keys and 8 or 12 rounds which are not applicable. The
> test vector whose answer begins "0x76 0xb8 0xe0 0xad 0xa0" is the one
> you want.

Also worth noting is that in RFC 7539, ChaCha has 96 bit IV/nonce and 32
bit counter instead of a 64 bit IV and 64 bit counter. The 32 extra IV
bits are used to initialize the state in the same way as 32 bits in the
counter. So its a simple matter of mapping the IV bits to the counter
bits and chacha will match the test vectors in RFC 7539. It tripped me
up when integrating the ChaCha core into my RFC 7539 ChaCha20_Poly1305 core.

https://github.com/secworks/chacha
https://github.com/secworks/ChaCha20-Poly1305

Note: the chacha-poly1305 core is not completed yet.
- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Alltid i harmonisk svängning.
========================================================================
 Joachim Strömbergson          Secworks AB          joachim@secworks.se
========================================================================
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