Method to secure a broadcasted event

• US 20060023876A1
• Filed: 03/09/2005
• Published: 02/02/2006
• Est. Priority Date: 03/10/2004
• Status: Abandoned Application

• Current Assignee: Nagracrad S.A. (Kudelski SA)
• Original Assignee: Nagracrad S.A. (Kudelski SA)
• Inventors: Kudelski, Henri, Ksontini, Rached
• Application Number:
  US11/074,688
• Publication Number:
  US 20060023876A1
• Time in Patent Office: Days
• US Class Current: 380/28
• CPC Class Codes: H04N 21/26606 for generating or managing entitlement messages, e.g. Entitlement Control Message [ECM] or Entitlement Management Message [EMM] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/4623 Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 7/167 Systems rendering the television signal unintelligible and subsequently intelligible
• 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

The aim of this invention is to propose a solution to prevent the modification of access conditions to an encrypted multimedia content. This aim is achieved by a method to secure an event with control words (CW), the use of this event by user units being subjected to access conditions (AC), said method comprising the following steps: generation of a pseudo-random number (RNG), formation of a control block (CB) by the association of the pseudo-random number (RNG) and the access conditions (AC), calculation of the control word (CW) by the application of a unidirectional function (F) on the control block (CB), use of the control word (CW) to encrypt the event, transmission of the control block (CB) to the user units.

Claims

1. Method to secure an event with control words, the use of this event by user units being subjected to access conditions, said method comprising the following steps:

generation of a pseudo-random number,

formation of a control block by the association of the pseudo-random number and the access conditions,

calculation of the control word by the application of a unidirectional function on the control block,

use of the control word to encrypt the event,

transmission of the control block to the user units.

2. Method according to claim 1, wherein the unidirectional function is initialized by an encryption key.

3. Method according to claim 1, wherein the current date is added at the control block and participates in the formation of the control word.

4. Method according to claim 2, wherein the control message includes the data block in clear.

5. Method according to claim 1, wherein the control message includes the data block in the form encrypted with a transmission key.

6. Method according to claim 1, wherein the control message includes two variables, which in combination with the access conditions and the unidirectional function, allow the generation of two control-words respectively.