ENCIPHERING KEY DISTRIBUTION SYSTEM FOR SUBSCRIPTION TV BROADCAST OR CATV SYSTEM

摘要

An enciphering key distribution system for use with a subscription television broadcast or cable television system is described. In the transmitter an address generator generates addresses of subscribers to which a first enciphering key for enciphering a TV signal is to be distributed and an enciphering key generator generates second enciphering keys in response to the addresses. The second keys are assigned a one-to-one correspondence with the subscribers. A multiplier produces the product of the second keys associated with all the subscribers and an adder adds the first key to that product. In the receiver of a subscriber, the received signal is divided by the particular second key assigned to the subscriber which reveals the first enciphering key which is then used to decipher the TV signal. The system simplifies receiver structure as data selectors for finding out the subscriber address are not necessary.