CHACHA20_CONSTANT_LEN
iv = nonce + CHACHA20_CONSTANT_LEN;
iv = nonce + CHACHA20_CONSTANT_LEN;
#define CHACHA20_NONCE_LEN (CHACHA20_CONSTANT_LEN + CHACHA20_IV_LEN)
iv = cpx->nonce + CHACHA20_CONSTANT_LEN;