Add salt/personalisation strings for Blake2b

[namelessjon]

They are exposed as options on the hash constructor. Strings are
zero-padded out to 16 bytes. If they are not provided then a blank
string is passed into the hash.

Need to add some tests, but I've checked against the sodium vectors at least.

[namelessjon]

I realise this needs a version check, because the function doesn't exist in older libsodiums, too

[tarcieri]

@namelessjon in the scrypt code, rather than an explicit version check, I was rescuing FFI::NotFoundError

[tarcieri]

@namelessjon perhaps you could use crypto_generichash_blake2b_salt_personal if available and fall back on crypto_generichash_blake2b for older versions of libsodium?

[namelessjon]

It's a little more complex, as that also needs to modify the calls and raise if salt/personal is passed in to a non-supporting implementation

[tarcieri]

Yep, it should only raise NotImplementedError if you pass in an unsupported parameter

[tarcieri]

@namelessjon mind if I release 3.1.0 with scrypt without this? I'd like to start using scrypt support

[tarcieri]

Well, I went ahead and shipped 3.1.0, so... 😉

[namelessjon]

I do take slightly longer than 6 minutes to reply, especially while asleep. 👅

That said, was the right call.

[namelessjon]

I will land this before you release 4.0.0. We can use that as an excuse to bump up the required library version up to 0.7.0 (as we'll need that for the SecretBuffer anyway). That way, there's no need to define the whole class two ways, to allow for sodium versions without the personal_salt blake variant.

[tarcieri]

Cool, added it to the 4.0 milestone

[namelessjon]

This has now been updated for the size_t fix I made in the mainline.

[tarcieri]

Plan on adding some tests?

[namelessjon]

Tests? What are those? ;)

More seriously, need to find some test vectors (probably from the sodium tests)

[namelessjon]

There now with some tests. The vectors I generated myself using the reference implementation of blake2.

[tarcieri]

Nice! Looking good from here

[namelessjon]

Merged!

[tarcieri]

w00p