A method for authenticating at least one subscriber during a data interchange between at least two subscribers is described. In the method, a first subscriber transmits a first data item (a challenge signal) to a second subscriber, the second subscriber processes the first data item using an algorithm...http://www.google.co.uk/patents/US20010021975?utm_source=gb-gplus-sharePatent US20010021975 - Method for authenticating at least one subscriber during a data interchange
