SilcBuffer silc_auth_public_key_auth_generate(SilcPublicKey public_key,
                                                  SilcPrivateKey private_key,
                                                  SilcRng rng,
                                                  SilcHash hash,
                                                  const void *id,
                                                  SilcIdType type);

    Generates Authentication Payload with authentication data. This is used
    to do public key based authentication. This generates the random data
    and the actual authentication data. Returns NULL on error and the
    encoded Authentication Payload on success.

    The `private_key' is used to sign the payload.  The `public_key', the
    and the `id' is encoded in the payload and signed.  If the `rng' is
    NULL then global RNG is used, if non-NULL then `rng' is used as
    random number generator.  Also random number is encoded in the
    payload before signing it with `private_key'.