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Re: [Cfrg] ChaCha20

Ilari Liusvaara <ilari.liusvaara@elisanet.fi> Fri, 08 August 2014 13:36 UTC

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Date: Fri, 08 Aug 2014 16:36:14 +0300
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
To: Watson Ladd <watsonbladd@gmail.com>
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Subject: Re: [Cfrg] ChaCha20
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On Thu, Aug 07, 2014 at 06:23:05PM -0700, Watson Ladd wrote:
> Dear all,
> In the past 6 years only one cryptanalysis result has been published
> against ChaCha, and that was against a variant before the final
> version was announced. While Salsa20 was an eStream finalist, ChaCha
> wasn't.
> 
> I'd like to see some more cryptanalytic attention on ChaCha: in
> particular are the differentials from "Latin Dances" still valid for
> the published version of ChaCha? What are the best differential
> characteristics? And can we figure this out quickly?

Trying to find paper about "Latin Dances", I ran into these:

https://eprint.iacr.org/2007/472
https://eprint.iacr.org/2012/065

Both seem to analyze final version of Chacha, and seemingly make
worse job than on Salsa (e.g. the first "breaks" Salsa8, but not
Chacha8).


-Ilari

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