+/**
+ * Hash the @a port and @a initiator and @a listener to
+ * calculate the "challenge" @a h_port we send to the other
+ * peer on #GNUNET_MESSAGE_TYPE_CADET_CHANNEL_OPEN.
+ *
+ * @param[out] h_port set to the hash of @a port, @a initiator and @a listener
+ * @param port cadet port, as seen by CADET clients
+ * @param listener peer that is listining on @a port
+ */
+void
+GCCH_hash_port (struct GNUNET_HashCode *h_port,
+ const struct GNUNET_HashCode *port,
+ const struct GNUNET_PeerIdentity *listener);
+
+