Verfahren und Gerät zur Verschlüsselung/Entschlüsselung von digitalen multiplexen Tonsignalen bei der Fernsehübertragung.

摘要

The present invention relates to methods and apparatus for encryption and decryption, respectively, of digital sound in television. The decryption takes place in two steps. The first step, encryption with running key, is achieved by adding modulo 2 a pseudo random sequence to the digital signal containing a sound information. The pseudo random sequence is preferably generated by a non-linear feedback register initialized by the control word. The second step involves encryption of the control word, thereby being transmitted to the receiver in ciphered form. The encryption is preferably achieved by a microprocessor also performing coding of the control word for forward error correction. The control word in turn is generated by a true random sequence generator. The invention enables an encryption that is secure against breaking without deteriorating the sound quality and also enables efficient handling of the key of the encryption.