+int write_datum_fd(int fd, const gnutls_datum_t* d);
+int write_datum_fd_with_length(int fd, const gnutls_datum_t* d);
+int write_data_fd_with_length(int fd, const gnutls_datum_t** d, unsigned int num);
+
+/* set up a datum from a null-terminated string */
+int datum_from_string(gnutls_datum_t* d, const char* str);
+
+/* keyid manipulations: */
+typedef unsigned char printable_keyid[16];
+
+void init_keyid(gnutls_openpgp_keyid_t keyid);
+void make_keyid_printable(printable_keyid out, gnutls_openpgp_keyid_t keyid);