Cryptographic and scrambling system utilising a shared medium passive optical network.

摘要

An improved method and apparatus encrypts and scrambles information cells transmitted on a telephone system local loop (11') from a central office to a plurality of user premises networks (14') via a shared medium passive optical network. Prior to transmission, the information cell is encrypted for security purposes and scrambled to improve its transmission properties by modulo 2 addition (218) of the information cell and a combined (214) encryption (211) and scrambling sum (212) pattern. At the other end of the passive optical network which is connected to user premises networks, the received encrypted and scrambled information cells are used to generate a processed cell by the modulo 2 addition of the received cell and a combined decryption and descramble sum pattern.