SilcBool silc_dh_compute_key(SilcDH dh, const SilcMPInt **z);

    Computes the secret key z = y' ^ x mod p, and returns the key to the
    `z' pointer sent as argument, unless the `z' is NULL. Returns FALSE if
    the computation could not be performed. The returned `z' must not be
    freed by the caller.