Two level encripting of RF signals

• US 4,531,021 A
• Filed: 08/13/1984
• Issued: 07/23/1985
• Est. Priority Date: 06/19/1980
• Status: Expired due to Term

• Current Assignee: TV/Com International, Inc.
• Original Assignee: Oak Industries, Inc. (Corning Incorporated)
• Inventors: Drake, David A., Bluestein, Leo I., Simpson, Larry W., Jedynak, Leo, Crandell, Paul E.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US06/640,212
• Time in Patent Office: 344 Days
• Field of Search: 176/1.5 R, 178/22.08, 178/22.09, 178/22.1, 375/2.1, 375/2.2, 358/123, 358/122
• US Class Current: 380/239
• CPC Class Codes: H04L 2209/601 Broadcast encryption
• CPC Class Codes: H04L 2209/80 Wireless
• 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

Abstract

A system for enciphering information bearing RF signals in digital form utilizes a first key common to all receivers. There are means to change the first key which means include, at the transmitter, means to send individual messages to each receiver, each message being itself enciphered in a second key which is peculiar to only one receiver or small group of receivers and which message includes a change of the first enciphering key. At each receiver there are means responsive to the correct address in a key change message which will thereafter permit the deciphering of the key change message in the key peculiar to the particular receiver or small group of receivers. The new first key is then used at the receiver to decipher subsequent information bearing messages.

Claims

1. In a subscription television system for broadcasting enciphered digital information bearing signals, means for using a first key to encipher the digital signals, means for simultaneously broadcasting the first key enciphered digital signals to multiple subscription television subscribers,

means for changing said first enciphering key applied to said digital signals, means for enciphering, in a second enciphering key, an information message as to the change in said first enciphering key, said second enciphering key being different for each of said multiple subscription television subscribers, with said information message including an address for each of said plurality of receivers, and means for transmitting said enciphered information message, separately to each of said subscription television subscribers, each such enciphered information message being enciphered in a different second key.

2. In a subscription television receiver for deciphering enciphered digital information bearing signals broadcast to multiple television subscribers, first deciphering means responsive to a subscriber common first deciphering key for deciphering said digital signals, means for changing said subscriber common first key including second deciphering means responsive to a message enciphered in a second key and which message includes a change in said first key, address means responsive to an address portion of said key change message for enabling said second deciphering means, said second deciphering means being responsive to a key peculiar to only one subscription television receiver, with each of the multiple subscription television receivers having a different second key.