SECURE CODING AND DECODING SYSTEM AND METHOD FOR TELEVISION PROGRAM SIGNALS

摘要

Parts of a composite video signal, such as segments (Fig. 2A) of each horizontal scan line, are stored in analog storage devices (52) and retrieved therefrom in a cyclic manner to rearrange them (Fig. 2B) and thereby encode the signal. The cyclic retrieval of the information from the storage devices is carried out on a selective basis in accordance with the binary state of a pseudo-random signal that is generated (46) independently at each of the encoding and decoding stations. Synchronization of the two independently generated signals is provided by a control word and an initialization word that are transmitted with (via 16) the encoded video signal, one of which is encrypted (26). Decryption of the word is carried out with a master key at each of the encoding and decoding stations (Fig. 3B).