A method of validating a passcode in a telephone network comprises using a hash function to hash the directory number of a subscriber to a passcode-controlled service and comparing an entered passcode with the output of the hash function. Each subscriber to a passcode-controlled service is provided with...http://www.google.de/patents/US6788775?utm_source=gb-gplus-sharePatent US6788775 - System and method for passcode validation during telephone call processing
