typedef struct { ... } SilcHashObject;

    This structure represents one hash function.  The hash function's
    name, digest length and block length are defined in the structure.
    This structure is then given as argument to the silc_hash_register.
    That function is used to register all hash functions into SILC.
    They can be then allocated by the name found in this structure by
    calling the silc_hash_alloc.