[PATCH v2 2/7] nest: Add Blake2s and Blake2b hash functions

[Ondrej Zajicek]

On Mon, Nov 16, 2020 at 11:31:14PM +0100, Toke Høiland-Jørgensen wrote:
> Toke Høiland-Jørgensen <toke at toke.dk> writes:
> 
> > @@ -169,6 +170,12 @@ const struct mac_desc mac_table[ALG_MAX] = {
> >    [ALG_SHA256] = 	HASH_DESC("Keyed SHA-256",	sha256,	SHA256),
> >    [ALG_SHA384] = 	HASH_DESC("Keyed SHA-384",	sha384,	SHA384),
> >    [ALG_SHA512] = 	HASH_DESC("Keyed SHA-512",	sha512,	SHA512),
> > +  [ALG_BLAKE2S] = 	{"Blake2s", BLAKE2S_SIZE, sizeof(struct blake2s_context),
> > +                         blake2s_bird_init, blake2s_bird_update,
> > +                         blake2s_bird_final, BLAKE2S_SIZE, BLAKE2S_BLOCK_SIZE},
> > +  [ALG_BLAKE2B] = 	{"Blake2b", BLAKE2B_SIZE, sizeof(struct blake2b_context),
> > +                         blake2b_bird_init, blake2b_bird_update,
> > +                         blake2b_bird_final, BLAKE2B_SIZE, BLAKE2B_BLOCK_SIZE},
> 
> Note that there's an ongoing discussion on the babel at ietf list about
> whether the output size of Blake2s ought to be truncated to 128 bits.
> 
> See:
> https://mailarchive.ietf.org/arch/msg/babel/9EIUxXvaGj-Zm9uktF0v1Zavb-g/
> 
> If anyone here has an opinion on this, please weigh in on that list;
> otherwise I plan to respin this series with an option to have both
> 128-bit and 256-bit outputs from Blake2s.

Hi

Well, if Blake2 has variants with reduced hash lengths, than these
lengths should be part of the hash name (like in SHA-2), even if only one
would be implemented. So they should have keywords like blake2s256.

Like in OpenSSL:
blake2b512        blake2s256        gost              md4
md5               rmd160            sha1              sha224
sha256            sha3-224          sha3-256          sha3-384
...

Or like in RFC 7693 section 4.

Also, even if Babel WG have selected 128-bit reduced hash length variant
as suggested variant, it would make sense to have full-length variants
implemented in BIRD as they are basic variants of that hash.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."