quarterRound method
Performs a quarter round of ChaCha20 according to the documentation by RFC
Implementation
void quarterRound(int a, int b, int c, int d) {
Uint32List result = transformFourInputsByChaChaQuarterRound(
Uint32List.fromList(
[chaChaState[a], chaChaState[b], chaChaState[c], chaChaState[d]]));
chaChaState[a] = result[0];
chaChaState[b] = result[1];
chaChaState[c] = result[2];
chaChaState[d] = result[3];
}