crypto: poly1305 - add Poly1305 core API
Expose a low-level Poly1305 API which implements the ε-almost-∆-universal (εA∆U) hash function underlying the Poly1305 MAC and supports block-aligned inputs only. This is needed for Adiantum hashing, which builds an εA∆U hash function from NH and a polynomial evaluation in GF(2^{130}-5); this polynomial evaluation is identical to the one the Poly1305 MAC does. However, the crypto_shash Poly1305 API isn't very appropriate for this because its calling convention assumes it is used as a MAC, with a 32-byte "one-time key" provided for every digest. But by design, in Adiantum hashing the performance of the polynomial evaluation isn't nearly as critical as NH. So it suffices to just have some C helper functions. Thus, this patch adds such functions. Acked-by: NMartin Willi <martin@strongswan.org> Signed-off-by: NEric Biggers <ebiggers@google.com> Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
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