Method and apparatus for encryption/decryption of digital multisound in television

DETAILED DESCRIPTION The invention allows a simple and secure encryption through a method, wherein the digital signal transmitted on the channel is scrambled by adding a binary pseudo random sequence modulo 2 to the digital sound, i.
e.
encryption with a running key.
To reproduce the original signal the same sequence is added on the receiver side.
The binary pseudo random sequence is generated by a pseudo random sequence generator.
The sequence is controlled by a so called control word, randomly generated on the transmitter side and changed at suitable intervals.
The control word is encrypted and transmitted to the receiver, where it is decrypted and transmitted to the pseudo random sequence generator of the receiver.
The invention also relates to apparatus for encryption and decryption, respectively, for carrying out the method.
Further embodiments of the invention are set forth in the accompanying claims.