title: Hack a Bike date: 2004-12-17 00:00:00 updated: 2012-02-19 23:21:04 author: 46halbe tags: update, hack a bike, call a bike previewimage: /images/01.jpg The "Call a Bike" system of the german railway company "Deutsche Bahn" offers bikes for self-hire in Berlin and other german cities. Sophisticated technology enables customers to rent a bike using their mobile phone. The system is advertised as being "unbreakable" but an article in our latest edition of our magazine "Die Datenschleuder" demonstrates the opposite: "Hack a Bike" uses advanced reengineering to turn the system upside down. The blinking bikes of "Deutsche Bahn" are part of the cityscape in Germany for quite some time now. An intricate system named ["Call a Bike"](http://www.callabike.de/) offers the option to rent a bicycle whereever you find one. The bikes themselves are not connected "online" but expect an unlock code that a customer can retrieve by calling a central number using his mobile phone. An article in our magazine [Datenschleuder](http://ds.ccc.de/) that has been passed along from an anonymous source details how the the system can be circumvented to gain free access to the bikes without calling anybody: ["Hack a Bike"](/hackabike/index.html) is a fine example of a true hack.