ML_DSA_RHO_PRIME_BYTES
uint8_t rho_prime[ML_DSA_RHO_PRIME_BYTES];
uint8_t derived_seed[ML_DSA_RHO_PRIME_BYTES + 2];
memcpy(derived_seed, rho_prime, ML_DSA_RHO_PRIME_BYTES);
derived_seed[ML_DSA_RHO_PRIME_BYTES] = index & 0xFF;
derived_seed[ML_DSA_RHO_PRIME_BYTES + 1] = (index >> 8) & 0xFF;