Cryptographic system using interchangeable key blocks and selectable key fragments

Abstract From the Canadian patent

A cryptographic system is used for the secure transmission of digitized signals to a plurality of receivers. At the transmission end a key consisting of two blocks, each including a plurality of key fragments, is generated For each, transmission session, different sets of key fragments may be periodically selected from one of the key blocks and used to encrypt the signals. Data indicative of the set selection is generated. The key is distributed to each receiver. The set selection data is transmitted to all receivers along with the encrypted signals and used to construct the key fragment set for decryption of the transmitted signals. During the transmission session, the other key block may …