SPHINCS: practical stateless hash-based signatures

Preliminary ref and avx2 implementations of SPHINCS-256 appear in the crypto_sign/sphincs256 directory inside the SUPERCOP benchmarking framework. The ref implementation is portable, and the avx2 implementation takes advantage of 256-bit vector instructions on Intel Haswell processors.

Version: This is version 2017.12.05 of the Software web page.