Method and apparatus for synchronizing encrypting and decrypting systems

Abstract From the Canadian patent

A synchronization method and corresponding apparatus for transmitting or storing encrypted data breaks the data into blocks and appends to each block an error detection code which is calculated from the encrypted data block plus a unique sequence number. The sequence number is generated by a local counter and may be the number of bits, bauds or, characters transmitted and received since a previous resynchronization. The error correcting code is transmitted or stored with the encrypted data block but although the sequence number is appended to the data block for error code calculation purposes it, is not actually transmitted or stored with the encrypted data and error correcting code. When …