SilcBuffer
    silc_auth_public_key_auth_generate_wpub(SilcPublicKey public_key,
                                            SilcPrivateKey private_key,
                                            const unsigned char *pubdata,
                                            SilcUInt32 pubdata_len,
                                            SilcHash hash,
                                            const void *id,
                                            SilcIdType type);

    Same as silc_auth_public_key_auth_generate but takes the public data
    (usually random data) as argument.  This function can be used when
    the public data must be something else than purely random or its
    structure mut be set before signing.