| 摘要 |
<p>A system for scrambling and descrambling complex signals, such as video signals, employs a system for encoding the decoding information, in the form of two security keys, directly onto the scrambled signal being transmitted, without the need of a second communications link for delivering one of the keys. In a video embodiment, several of the video lines during the vertical scan period are encoded with identification information which identifies a specific one of the multiple decoders at the receiving stations, and a scrambled security code (13). The security code can only be descrambled by the decoder which is specifically identified in the identification code. A security code descrambling algorithm which is specific to the respectively associated decoder is permanently installed in the decoder along with the identification information (14). The relationship between the security code descrambling algorithm and the identification code for each of the decoders is stored in a memory at the transmitting station. A field code (16) is transmitted in the scrambled complex signal which, when used in conjunction with the unscrambled security code, provides the decoder with the information needed to identify the scrambling distortion which had been introduced into the complex signal.</p> |
