Jeffrey Walton <[email protected]> writes:

> I hope I'm not crossing my wires, but doesn't ChaCha core require a
> counter addition? 

Sure, but nettle's _chacha_core function (what I've implemented so far
for ppc) does a single block, and doesn't modify the counter. Variants
like _chacha_3core (currently implemented for ARM Neon only) need to
update the counter.

> There are some fundamental differences between Bernstein's ChaCha and
> the IETF's ChaCha used in TLS. Bernstein's ChaCha uses a 64-bit
> counter.

That's a bit messy, but nettle supports both variants. To use the ietf
version, either use the the chacha_poly1305_* aead functions, or, for
chacha only, the functions chacha_set_nonce96 and chacha_crypt32.

And there are tests for 32-bit wraparound in both cases.

Regards,
/Niels

-- 
Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
Internet email is subject to wholesale government surveillance.
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