void silc_hash_make(SilcHash hash, const unsigned char *data,
                        SilcUInt32 len, unsigned char *return_hash);

    Computes the message digest (hash) out of the data indicated by
    `data' of length of `len' bytes.  Returns the message digest to the
    `return_hash' buffer which must be at least of the size of the
    message digest the `hash' produces.