I haven't benchmarked TweetNaCl's performance yet, but I think that goes way too far into making the code completely unreadable. The 80%/10% number I gave is against the ref10 implementation.
Please note that like BearSSL, my implementations are alpha-quality. Further, I'm not suggesting anyone use these in production. If I do so myself and it blows up in my face, it'll only have harmed me, and I'll only have myself to blame.
(Also, I'm really bad when it comes to source code comments, sorry. The why really needs you to read the research papers; the how is mostly self-evident. The remaining one-letter variable names were used to match the papers, and because I couldn't think of more descriptive terms.)
If you're using modern C++ you might consider using SaferCPlusPlus[1] for improved memory safety. Safe, fast compatible direct substitutes for C++'s unsafe elements (pointers, arrays, vectors, even references are technically unsafe). Small, easy to use, no dependency risk, and can be optionally "disabled" with a compile-time directive. It's the best answer to the Rust crowd who (justifiably) point out the inevitability of memory bugs in large enough C++ code bases.
Compare theirs: https://tweetnacl.cr.yp.to/20140427/tweetnacl.c
To mine:
https://gitlab.com/higan/higan/blob/master/nall/elliptic-cur...
https://gitlab.com/higan/higan/blob/master/nall/elliptic-cur...
https://gitlab.com/higan/higan/blob/master/nall/cipher/chach...
https://gitlab.com/higan/higan/blob/master/nall/mac/poly1305...
https://gitlab.com/higan/higan/blob/master/nall/hash/sha256....
Please note that like BearSSL, my implementations are alpha-quality. Further, I'm not suggesting anyone use these in production. If I do so myself and it blows up in my face, it'll only have harmed me, and I'll only have myself to blame.
(Also, I'm really bad when it comes to source code comments, sorry. The why really needs you to read the research papers; the how is mostly self-evident. The remaining one-letter variable names were used to match the papers, and because I couldn't think of more descriptive terms.)