let mut chacha = ChaCha20Poly1305RFC::new(key, &nonce, h);
if !chacha.decrypt(&cyphertext[0..cyphertext.len() - 16], res, &cyphertext[cyphertext.len() - 16..]) {
let mut chacha = ChaCha20Poly1305RFC::new(key, &nonce, h);
if !chacha.decrypt(&cyphertext[0..cyphertext.len() - 16], res, &cyphertext[cyphertext.len() - 16..]) {