A scramble system can effectively prevent a scrambled broadcast from being viewed illegally. In a scramble system in which a video signal scrambled by a scrambling apparatus (10) is descrambled by a decoding apparatus (20), an identification code that specifies the decoding apparatus (20) is inserted...http://www.google.com.au/patents/US5579391?utm_source=gb-gplus-sharePatent US5579391 - TV scramble system for preventing illegal reception
