out[:len(plaintext)], additionalData) copy(out[len(plaintext):], tag[:]) } func open(out []byte, g *GCM, nonce, ciphertext, data []byte) error { switch { case useGCM: return openKMA(out, g, nonce, ciphertext, data) case useGHASH: return openAsm(out, g, nonce, ciphertext, data) default: return openGeneric(out, g, nonce, ciphertext, data) } } func openAsm(out []byte, g *GCM, nonce, ciphertext, additionalData []byte) error { var counter, tagMask [gcmBlockSize]byte deriveCounter(&g.hashKey, &counter, nonce) counterCrypt(g,...