derive_key
void derive_key(u_int32_t, int, u_int8_t *, size_t,
derive_key(kdfhint->generic.type, kdfhint->rounds,
derive_key(kdfinfo->pbkdf.generic.type, kdfinfo->pbkdf.rounds,
if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,