+/* Compute Hashed Message Authentication Code with SHA-1, over BUFFER
+ data of BUFLEN bytes using the KEY of KEYLEN bytes, writing the
+ output to pre-allocated 20 byte minimum RESBUF buffer. Return 0 on
+ success. */
+int
+hmac_sha1 (const void *key, size_t keylen,
+ const void *in, size_t inlen, void *resbuf);
+