ossl_curve448_scalar_mul
ossl_curve448_scalar_mul(challenge_scalar, challenge_scalar, secret_scalar);
void ossl_curve448_scalar_mul(curve448_scalar_t out,
ossl_curve448_scalar_mul(s, s, ossl_curve448_scalar_one); /* ham-handed reduce */
ossl_curve448_scalar_mul(s, t1, ossl_curve448_scalar_one);