Security, Symmetric Encryption, Cryptography, Encryption.
x[4], x[ 9], x[14]); // diagonal 4 } for (i = 0; i < 16; ++i) out[i] = x[i] + in[i]; // Last Block of addition } Note the last Block. Here the Block is added to itself after 20 rounds. This ensures just reversibility of the rounds would not break ChaCha.If this were not there one would just reverse