An encryption arrangement for multiple encryption of television programs.
A system according to embodiments of the present invention multiple
encrypts only a portion of the data required for full presentation of a
television program to permit coexistence of multiple conditional access
encryption systems associated with multiple manufacturer's set-top boxes
within a single system. In one embodiment, a time slicing technique is
used to encrypt portions of a program on a time allocated basis. By only
encrypting a portion of the program, dramatically less bandwidth is
consumed than the alternative of multiple encryption of all program data,
thus permitting a larger number of programs to be carried over the same
bandwidth while permitting coexistence of multiple conditional access
systems in a single cable television system.