I took some liberty here, but this is a straightforward derivation of XSalsa20. I trust XChacha20 just as strongly as I trust Chacha20. The same cannot be sai

I took some liberty here, but this is a straightforward derivation of XSalsa20. I trust XChacha20 just as strongly as I trust Chacha20. The same cannot be said about my implementation however. I haven't found test vectors for XChacha20, so for now I have to rely on code review (only my own eyes so far) to ascertain its correctness. Not ideal. Also I don't favour XChacha20 over Chacha20, because it is slightly slower to initialise. If a 64-bit nonce is enough, I'll use Chacha20. Maybe I should make this clear in my article.