Ostiary!

Ostiary ClientOstiary uses a secure challenge/ response mechanism to run arbitrary scripts on a server. One particular use is opening ports in firewall configurations similar to port knocking tools but without the risk of replay attacks (e.g. in a public WiFi network. The source code for Ostiary can be found here:http://ingles.homeunix.net/software/ost/index.html(c) Ray Ingles (Ostiary)(c) Ulrich Drepper (SHA256-based Unix crypt implementation)(c) Christian Mueller (iOS Client)