SilcBool silc_pkcs_sign(SilcPrivateKey private_key,
                            unsigned char *src, SilcUInt32 src_len,
                            unsigned char *dst, SilcUInt32 dst_size,
                            SilcUInt32 *dst_len, SilcBool compute_hash,
                            SilcHash hash);

    Generates signature with the private key.  Returns FALSE on error.
    If `compute_hash' is TRUE the `hash' will be used to compute a
    digest over the `src'.  The `hash' must always be valid.