Patent ID: 7539315
Filing Date: 2009-05-26
Classification: H04L

Abstract:
1. A cryptographic communication system comprising: a key distribution server for distributing a key used to decrypt encrypted information; and a specific number of subscriber terminals using said information, wherein said key distribution server distributes: an encrypted first group key used to decrypt said information; individual decryption information respectively corresponding to each one of said specific number of subscriber terminals and used to perform decryption of said first group key; and individual terminal unique key update information respectively corresponding to each one of said specific number of subscriber terminals and used to perform a part of decryption of a second group key, said second group key being updated after a group key is updated, and wherein said specific number of subscriber terminals decrypt said first group key distributed from said key distribution server by use of results obtained by processing operations performed based on said terminal unique key update information previously obtained and used to decrypt said first group key, as well as by use of said decryption information distributed from said key distribution server.