ChaCha20 Algorithm

ChaCha20 is a symmetric stream cipher that generates a pseudorandom keystream from a 256 bit key, a nonce and a block counter through twenty rounds of addition, rotation and XOR operations arranged in a 4x4 matrix of 32 bit words, which is then combined with the plaintext to produce ciphertext. It was designed by Daniel J. Bernstein in 2008 as a variant of his earlier Salsa20 cipher offering improved diffusion per round. It is widely deployed today, notably paired with the Poly1305 authenticator in the ChaCha20-Poly1305 construction used by TLS and several major software products for its speed on hardware without dedicated AES instructions.