-bool digest_open_by_name(struct digest *, const char *);
-bool digest_open_by_nid(struct digest *, int);
-bool digest_open_sha1(struct digest *);
-bool digest_create(struct digest *, void *indata, size_t inlen, void *outdata);
-bool digest_verify(struct digest *, void *indata, size_t inlen, void *digestdata);
-int digest_get_nid(struct digest *);
+extern digest_t *digest_open_by_name(const char *name, int maclength) __attribute__((__malloc__));
+extern digest_t *digest_open_by_nid(int nid, int maclength) __attribute__((__malloc__));
+extern void digest_close(digest_t *);
+extern bool digest_create(digest_t *, const void *indata, size_t inlen, void *outdata) __attribute__((__warn_unused_result__));
+extern bool digest_verify(digest_t *, const void *indata, size_t inlen, const void *digestdata) __attribute__((__warn_unused_result__));
+extern bool digest_set_key(digest_t *, const void *key, size_t len) __attribute__((__warn_unused_result__));
+extern int digest_get_nid(const digest_t *);
+extern size_t digest_keylength(const digest_t *);
+extern size_t digest_length(const digest_t *);
+extern bool digest_active(const digest_t *);
+
+#endif