Television signal scrambling system and method

• US 4,995,080 A
• Filed: 07/16/1990
• Issued: 02/19/1991
• Est. Priority Date: 08/04/1988
• Status: Expired due to Term

• Current Assignee: Zenith Electronics Corporation (LG Corporation)
• Original Assignee: Zenith Electronics Corporation (LG Corporation)
• Inventors: Citta, Richard W., Bestler, Caitlin B., Long, Michael E.
• Primary Examiner(s): Buczinski, Stephen C.
• Assistant Examiner(s): GREGORY, BERNARR E
• Application Number:
  US07/552,375
• Time in Patent Office: 218 Days
• Field of Search: 380/5, 380/10-17, 380/19, 380/20, 380/21, 380/49, 358/349, 358/145, 358/147
• US Class Current: 380/239
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 21/2543 Billing , e.g. for subscription services payment schemes, architectures or protocols G06Q20/00; e-commerce G06Q30/00; arrangements for billing for the use of broadcast information or broadcast-related information H04H60/21
• CPC Class Codes: H04N 21/4627 Rights management associated to the content security in data switching network management H04L41/28; security management or policies for network security H04L63/20; access security in wireless networks H04W12/08
• CPC Class Codes: H04N 21/47211 for requesting pay-per-view content payment schemes payment architectures or payment protocols G06Q20/00, G07F
• CPC Class Codes: H04N 21/4753 for user identification, e.g. by entering a PIN or password cryptographic authentication protocols H04L9/32; networks authentication protocols H04L63/08
• CPC Class Codes: H04N 21/6582 Data stored in the client, e.g. viewing habits, hardware capabilities, credit card number arrangements where receivers interact with the broadcast H04H20/38
• 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
• CPC Class Codes: H04N 7/17327 with deferred transmission or handling of upstream communications

Abstract

A method of operating a pay per view (PPV) television system includes transmitting global data packets alternately encrypted with two different session keys. Subscriber terminals store three session keys, and automatically sequence through the session keys in an ateempt to decrypt the data packets. A program tag in the global data packet identifies a television program and a memory location in the subscriber authorization memory and may also include a tag identifying an upcoming program for which the subscriber may self-authorize his terminal by accessing the memory location identified by the PPV tag. The program tag is required to enable the subscriber terminal descrambling means to descramble the accompanying television program. Subscriber terminals are periodically polled by addressed data packets whereupon the contents of their authorization memories are sent to the cable heat-end for billing purposes. After successful polling, a new session key is downloaded to the subscriber in an addressed data packet. After polling of all subscribers, the memory location identified by the PPV tag is cleared by means of a global data packet encrypted in the new session key which only polled subscriber terminals have. An unpolled subscriber terminal needs to be polled before it receives the new session key.

Claims

1. A method of operating a television scrambling system including a plurality of subscriber terminals having selectively controllable descrambling means and a first session key comprising the steps of:

alternately transmitting a scrambled television signal with a data packet encrypted with said first session key and transmitting said scrambling television signal with said data packet encrypted with a second session key, to all subscriber terminals to permit operation of said descrambling means to descramble the television signal by subscriber terminals having said first session key or said second session key;

transmitting said second session key to authorized subscriber terminals only; and

alternately transmitting said scrambled television signal with a data packet encrypted with said second session key and transmitting said scrambled television signal with said data packet encrypted with a third session key to all subscriber terminals, whereby subscriber terminals with said first session key and without said second session key or said third session key cannot descramble said television signal.

2. The method of claim 1 wherein said second session key is downloaded in data packets addressed to individual subscribers.

3. The method of claim 2 wherein each subscriber terminal stores two session keys that are changeable by means of addressed data packets;

and

wherein each subscriber terminal sequentially tries its two session keys in an attempt to decrypt the encrypted data packets.

4. The method of claim 3, further including the steps of:

attempting to poll subscriber terminals to determine their status; and

downloading said second session key only to subscriber terminals that have been successively polled.

5. A method of operating a pay per view television signal system including a plurality of subscriber terminals, each having an authorization memory comprising a plurality of memory locations for storing authorization data, unscrambling means for unscrambling a received television program in response to authorization data stored in a memory location identified by a simultaneously received program tag and a first session key for decrypting data packets, comprising the steps of:

transmitting a program tag, identifying a memory location of said authorization memory corresponding to a selected pay per view television program, in a data packet alternately encrypted with said first session key and a second session key;

permitting subscriber terminals having said first session key to input authorization data to said memory location;

transmitting said pay per view television program together with a program tag identifying said memory location;

polling each subscriber terminal to read the status of said memory location;

transmitting said second session key in individually addressed data packets to successfully polled subscriber terminals only;

clearing the authorization data at said memory location by a transmitted data packet encrypted in said second session key; and

transmitting a program tag identifying a memory location corresponding to a selected pay per view television program in a data packet alternately encrypted with said second session key and a third session key.

6. The method of claim 5 wherein said television signal has two fields and wherein the alternate encryption of said data packets occurs in said two fields of the transmitted television signal.