Trick play of encrypted data in a conditional access signal

• US 20050201556A1
• Filed: 05/27/2003
• Published: 09/15/2005
• Est. Priority Date: 06/12/2002
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Verslegers, Rudi Jaak Jozef, Rijckaert, Albert Maria Arnold
• Application Number:
  US10/517,480
• Publication Number:
  US 20050201556A1
• Time in Patent Office: Days
• US Class Current: 380/37
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00231 wherein the key is obtained from a local external medium, e.g. a card
• CPC Class Codes: G11B 20/00333 the key being stored in header data, e.g. in sector headers
• CPC Class Codes: G11B 20/00507 wherein consecutive physical data units of the record carrier are encrypted with separate encryption keys, e.g. the key changes on a cluster or sector basis
• CPC Class Codes: G11B 27/005 Reproducing at a different information rate from the information rate of recording for television signals H04N5/783
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: H04N 2005/91364 the video signal being scrambled
• 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 21/4334 Recording operations recording of a television signal H04N5/76; arrangements for recording or accumulating broadcast information or broadcast-related information H04H60/27
• CPC Class Codes: H04N 21/440281 by altering the temporal resolution, e.g. by frame skipping television signal recording using magnetic recording on tape for reproducing at a rate different from the recording rate H04N5/783
• CPC Class Codes: H04N 5/783 Adaptations for reproducing at a rate different from the recording rate
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• 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

An incoming data stream contains a stream of encrypted data and a stream of messages. Data in successive segments of the stream of encrypted data is decryptable with successive decryption information from the messages. The stream of encrypted data is stored and items with decryption information from the stream of messages are stored. Synchronization information is stored that links respective points in the stored stream of encrypted data to respective ones of the items with decryption information. The synchronization is stored so that it is retrievable independent of the stream. During trick replay a stored part of the stream of encrypted data is replayed in an abnormal temporal pattern. The items with decryption information are retrieved for the points in said stored part during said replaying. The retrieved items are combined with decryption information of the stream during replay at times selected under control of the synchronization information, the items which are combined being selected and/or a time when the items are combined with the stream being selected, dependent on the synchronization information and the abnormal temporal pattern.

Claims

1. A method of processing an incoming data stream that contains a stream of encrypted data and a stream of messages, data in successive segments of the stream of encrypted data being decryptable with successive decryption information from the messages, the method comprising

storing the stream of encrypted data;

storing items with decryption information from the stream of messages;

storing synchronization information linking respective points in the stored stream of encrypted data to respective ones of the items with decryption information, the synchronization being stored so that it is retrievable independent of the stream;

replaying a stored part of the stream of encrypted data in an abnormal temporal pattern;

retrieving the items with decryption information for the points in said stored part during said replaying;

combining the retrieved items with decryption information with the stream during replay at times selected under control of the synchronization information, the items which are combined being selected and/or a time when the items are combined with the stream being selected, dependent on the synchronization information and the abnormal temporal pattern.

2. A method according to claim 1, wherein the stream of messages contains a plurality of messages that repeat the same decryption information, the method comprising

subsampling messages from said stream of messages, only items with decryption information from subsampled ones of the messages being stored, and

the synchronization information linking groups of points in the stored stream of encrypted data to respective ones of the subsampled items.

3. A method according to claim 2, the method comprising

detecting a transition after which the messages contain decryption information different from decryption information in messages before the transition;

subsampling at least one of the subsampled messages at a predetermined position relative to the transition.

4. A method according to claim 1, wherein the method comprises

constructing a list of data pointers to selected parts of the stream of encrypted data, each data pointer being associated with a selected one of the items of decryption information that enables decryption of the encrypted data pointed at by the pointer;

determining, during replay, whether replay will access encrypted data in the part pointed at by a particular pointer in said list;

upon said determining using the list to supply decryption information from the item associated with the particular pointer.

5. A method according to claim 1, wherein the encrypted data contains image frames, and update information for deriving additional image frames by updating the image frames, the method comprising

constructing a list of data pointers to selected parts of the stream of encrypted data that contain image frames, each data pointer being associated with a selected one of the items of decryption information that enables decryption of the encrypted data pointed at by the pointer;

selecting, during replay, the parts of the stream pointed at by pointers in the list;

using the list to supply decryption information from the item associated with each pointer.

6. A method according to claim 1, the method comprising

decrypting the items of decryption information from the incoming data stream and re-encrypting the items of decryption information with a recording key prior to storage;

storing the reencrypted items of decryption information separately from the stream of encrypted data.