Simon Josefsson <si...@josefsson.org> writes:
> It is a hash function, just not a cryptographic hash function.
>
> Below is an updated patch. What do you think?
Looks pretty good. I'm not sure about naming.
Besides that, a few minor comments. Some of them boil downto simply
inlining current _salsa20 into salsa20_core, and have salsa20_hash call
salsa20_core rather than _salsa20. Do you see any drawbacks with that?
> +static void
> +_salsa20 (unsigned rounds,
> + uint32_t *x)
No need to use _ in the name of a static-declared function.
> + unsigned i;
> +
> + for (i = 0; i < rounds; i += 2)
> + {
> + QROUND(x[0], x[4], x[8], x[12]);
> + QROUND(x[5], x[9], x[13], x[1]);
> + QROUND(x[10], x[14], x[2], x[6]);
> + QROUND(x[15], x[3], x[7], x[11]);
> +
> + QROUND(x[0], x[1], x[2], x[3]);
> + QROUND(x[5], x[6], x[7], x[4]);
> + QROUND(x[10], x[11], x[8], x[9]);
> + QROUND(x[15], x[12], x[13], x[14]);
> + }
Any reason not to do the final addition here? Would need separate input
and output arguments, and be organized as
x = input (memcpy)
do the rounds
dst = input + x (loop)
We need a single temporary array somewhere if we want to allow in-place
operation, and this may be that right place. And then we have
implemented all of salsa20_core.
> +void
> +salsa20_hash (unsigned rounds,
> + uint8_t *dst,
> + const uint8_t *src)
> +{
> + uint32_t x[SALSA20_INPUT_LENGTH];
> + unsigned i;
> +
> + for (i = 0; i < SALSA20_INPUT_LENGTH; i++)
> + x[i] = LE_READ_UINT32(&src[i * 4]);
> +
> + _salsa20 (rounds, x);
> +
> + for (i = 0; i < SALSA20_INPUT_LENGTH; i++)
> + {
> + uint32_t t = x[i] + LE_READ_UINT32(&src[i * 4]);
Seems unnecessary to convert (using LE_READ_UINT32) the same data twice.
> +void
> +salsa20_core (unsigned rounds,
> + uint32_t *dst,
> + const uint32_t *src)
> +{
> + uint32_t x[SALSA20_INPUT_LENGTH];
> + unsigned i;
> +
> + for (i = 0; i < SALSA20_INPUT_LENGTH; i++)
> + x[i] = src[i];
This should be plain memcpy.
Regards,
/Niels
--
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
Internet email is subject to wholesale government surveillance.
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