pub fn hchacha20(key: &[u8; 32], nonce: &[u8; 16]) -> [u8; 32]Expand description
HChaCha20 (draft-irtf-cfrg-xchacha §2.2): the ChaCha20 rounds over key and a 128-bit nonce in
the counter-and-nonce words, without the final addition, returning the first and last rows — a
subkey as uniform as the key, one per nonce.