US 6,714,649 B1 · Pay broadcasting system with enhanced security against illegal access to a down loaded program in a subscriber terminal

Abstract

In a pay broadcasting system, data of a broadcast program is scrambled with a scramble key updated in a short period. The scramble key is encrypted with a first key assigned to the subscriber terminal. The first key is encrypted with a first master key set in the subscriber terminal. The security of a broadcast program stored for subsequent use in the subscriber terminal is enhanced as follows. A central station generates a second key-encrypted scramble key by encrypting the scramble key with a second key different from the first key and changeable in an interval shorter than a update interval of the first key; generates an encrypted second key by encrypting the second key with a second master key which has been commonly issued to subscriber terminals of the system; and broadcast the second key-encrypted scramble key and the encrypted second key together with the scrambled data of the program, the first key-encrypted scramble key and the encrypted first key in a multiplexed manner. When a broadcast program is to be stored, the subscriber terminal stores the scrambled data of the broadcast program and the second key-encrypted scramble key; decrypt the encrypted second key with the second master key into the second key, which is added to a stored program second key list. If the stored program is to be executed, the second key-encrypted scramble key is decrypted with a corresponding one of the second keys in the stored program second key list into a decrypted scramble key; and the scrambled data of the broadcast program is unscrambled with the decrypted scramble key.

Claims17

Dependent claims

In a pay broadcasting system including a central station and a subscriber terminal wherein data of a broadcast program is scrambled with a scramble key updated in a short period, the scramble key being encrypted with a first key assigned to the subscriber terminal, the first key being encrypted with a first master key set in the subscriber terminal, a method of enhancing security of a broadcast program stored for subsequent use in the subscriber terminal, the method including the steps of:

the central station
generating a second key-encrypted scramble key by encrypting said scramble key with a second key, said second key being different from said first key and changeable in an interval shorter than a update frequency of said first key;
generating an encrypted second key by encrypting said second key with a second master key which has been commonly issued to subscriber terminals served by said central station;
and
broadcasting said second key-encrypted scramble key and said encrypted second key together with said scrambled data of said broadcast program, said first key-encrypted scramble key and said encrypted first key in a multiplexed manner, and
the subscriber terminal in storing said broadcast program, storing said scrambled data of said broadcast program and said second key-encrypted scramble key, decrypting said encrypted second key with said second master key into said second key and adding said second key to a stored program second key list;
if said stored program is to be executed, decrypting said second key-encrypted scramble key with a corresponding one of said second keys in said stored program second key list into a decrypted scramble key;
and
unscrambling said scrambled data of said broadcast program with said decrypted scramble key.

6 more elements

A subscriber terminal capable of storing a received program and executing one of the stored programs later with an enhance security against illegal access to the stored programs in a pay broadcasting system, wherein data of the received program has been scrambled with a scramble key, the subscriber terminal including:

means for demultiplexing said received program into scrambled program data, first encrypted scramble keys encrypted with first keys for subscriber terminals in the broadcasting system and encrypted first keys encrypted with respective first master keys;
means for using said scrambled program data, said first encrypted scramble keys and said encrypted first keys to present said received program to a user in real time;
said demultiplexing means further providing a second encrypted scramble key encrypted with a second key different from said first key and changeable in an time interval shorter than a update interval of said first key and an encrypted second key encrypted with a second master key which has been commonly issued to said subscriber terminals;
means, responsive to a recording command to store said received program from said user, for storing said scrambled program data and said second encrypted scramble key;
means, responsive to said recording command, for decrypting said encrypted second key with said second master key into said second key and adding said second key to a stored program second key list;
means, responsive to a execution command to execute said stored program, for decrypting said second encrypted scramble key with a corresponding one of said second keys in said stored program second key list into a decrypted scramble key;
and
means for unscrambling said scrambled program data with said decrypted scramble key.

5 more elements

Dependencies are inferred from the claim text.

Pay broadcasting system with enhanced security against illegal access to a down loaded program in a subscriber terminal

Life of this patent

Pay broadcasting system with enhanced security against illegal access to a down loaded program in a subscriber terminal

Life of this patent

Abstract

Claims17