Pre-payment television system using a memory card associated with a decoder

• US 5,134,656 A
• Filed: 10/19/1990
• Issued: 07/28/1992
• Est. Priority Date: 02/22/1989
• Status: Expired due to Term

• Current Assignee: Nagra Plus SA (Kudelski SA)
• Original Assignee: Kudelski SA
• Inventors: Kudelski, Andre
• Primary Examiner(s): SWANN, TOD R
• Application Number:
  US07/598,689
• Time in Patent Office: 648 Days
• Field of Search: 380/16, 380/20, 380/21, 380/43, 380/45, 380/46, 380/48, 380/49, 380/50
• US Class Current: 380/228
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58

Abstract

According to the invention, on the emitter side, a number generator (10) delivers a random code (XAL) which is sent to the input of a master card (11) which ciphers such code according to a predetermined key (100), the code thus ciphered is broadcast with the video signal, a first device (17) receives, on the one hand, the random code (XA) and, on the other hand, the code ciphered by the master card (11) and effects a predetermined numerical combination of these two codes, such combination forming the initialization word of a pseudo-random generator (12) intended to provide a table of codes for scrambling the video signal and, on the receiver side, the ciphered code received is deciphered by a customer card (13), a second device (18) receives at the inputs, on the one hand, the ciphered code and, on the other hand, the code deciphered (XA) by the customer card (13) and effects a numerical combination of these two codes which is similar to the combination of the first device (17).

Claims

1. A pay-television system using a memory card associated with a decoder, wherein, on an emission side, a digital generator (10) supplies a random code (XA) which is sent to an input of a main card (11) which enciphers said random code, by using a predetermined key (100), and the enciphered code is included in a broadcasted video signal, a first device (17) has inputs and receives at its inputs, on the one hand, said random code (XA) and, on the other hand, the code (XB) enciphered by the main card (11) and carries out a determined digit combination of those two codes, this combination forming the initialization word of a pseudo-random generator (12) which is intended to supply a code table designed to scramble the video signal, and on the reception side, the decoder receives the enciphered code (XB) that is deciphered by a subscriber card (13), a second device (18) has inputs and receives at its inputs, on the one hand, the enciphered code (XB) and, on the other hand, the code deciphered (XB) by the subscriber card (13) and carries out a digital combination of those two codes, this combination being identical to the one of the first device (17), the result of this combination constituting the initialization word for another pseudo-random generator (14) supplying a code table identical to the one of the emission, this code table being designed to unscramble the video signal.

2. A pay-television system according to claim 1 wherein the first (17) nd the second (18) devices carry out the same digital combination whose function is such that the reciprocal function can be determined only by a complete test.

3. A pay-television system according to claim 2 wherein the first (17) and the second (18) devices carry out the same digital combination of binary numbers by way of using an exclusive or logical function.