Method and System for Ensuring Sequential Playback of Digital Media

• US 20100082970A1
• Filed: 09/30/2008
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lindahl, Aram, James, Bryan J.
• Granted Patent: US 9,077,526 B2
• Time in Patent Office: Days
• US Class Current: 713/150
• CPC Class Codes: G06F 21/107 License processing; Key processing
• CPC Class Codes: H04L 2209/603 Digital right managament [DRM]
• CPC Class Codes: H04L 9/08 Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords network architectures or network communication protocols for supporting key management in a packet data network H04L63/06
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

Techniques for ensuring that media playback proceeds sequentially through media content of a digital media asset are disclosed. In one embodiment, distinct portions (e.g., segments) of a digital media asset can be separately encrypted such that on playback decoded data being output from at least one prior portion can be used to derive a cryptographic key that is used in decrypting a subsequent portion of the digital media asset.

Claims

1. A method for requiring sequential playback of a digital media asset, said method comprising:

(a) accessing decryption instructions associated with the digital media asset;

(b) accessing a first segment of the digital media asset;

(c) decrypting the first segment of the digital media asset with a decryption key;

(d) decoding the decrypted first segment to obtain decoded media data;

(e) outputting the decoded media data pertaining to the decrypted first segment to an output device;

(f) determining a sequential key for a next segment of the digital media asset based on at least a portion of the decoded media data pertaining to the decrypted first segment;

(g) accessing the next segment of the digital media asset; and

(h) decrypting the next segment of the digital media asset based on at least the sequential key.

2. A method as recited in claim 1, wherein said method further comprises:

(i) decoding the decrypted next segment to obtain decoded next media data; and

(j) outputting the decoded next media data pertaining to the decrypted next segment to the output device.

3. A method as recited in claim 2, wherein said decrypting (h) of the next segment of the digital media asset is further based on the decryption key.

4. A method as recited in claim 2, wherein said decrypting (h) of the next segment of the digital media asset is further based on another decryption key.

5. A method as recited in claim 1, wherein said determining (f) of the sequential key for the next segment of the digital media asset is based on at least a portion of the decoded media data pertaining to the decrypted first segment.

6. A method as recited in claim 1, wherein said determining (f) of the sequential key for the next segment of the digital media asset is based on at least a portion of the decoded media data pertaining to the decrypted first segment and a sequential key pertaining to an earlier segment.

7. A method as recited in claim 1, wherein the first segment and the next segment pertain to sequential segments of a video or audio asset.

8. A method as recited in claim 1, wherein said determining (f) is performed after the decoded media data pertaining to the decrypted first segment is output to the output device.

9. A method as recited in claim 1,

wherein said method further comprises:

temporarily storing the sequential key in a cache store, and

wherein said determining (f) comprises;

(f1) checking the cache store to determined whether the sequential key is available from the cache store; and

(f2) if said checking (f1) indicates that the sequential key is available from the cache store, generating the sequential key for the next segment of the digital media asset based on at least a portion of the decoded media data pertaining to the decrypted first segment.

10. A method as recited in claim 1, wherein said method further comprises:

decrypting the digital media asset prior to said accessing (a) of the decryption instructions and prior to said accessing (b) of the first segment of the digital media asset.

11. A media playback device, comprising:

a storage device configured to store encrypted digital media content;

a decryption engine configured to decrypt the encrypted digital media content to obtain encoded media content, the decryption of the encrypted digital media content requiring a content access key and a sequential key;

a decoder configured to produce decoded data from the encoded media content;

an output device configured to output the decoded data; and

a sequential key generator operatively connected to said decoder and said decryption engine, said sequential key generator being configured to produce different sequential keys for use by said decryption engine in decoding each of a plurality of different segments of the encrypted digital media content.

12. A media playback device as recited in claim 11, wherein the decoded data from an earlier segment is used to produce the sequential key for a subsequent segment.

13. A media playback device as recited in claim 11, wherein the decoded data from an earlier segment and the sequential key for at least one earlier segment are used to produce the sequential key for a subsequent segment.

14. A media playback device as recited in claim 11, wherein said media playback device further comprises a cache store configured to temporarily store the different sequential keys produced by said sequential key generator.

15. A system for cryptographically ensuring sequential playback of a digital media asset, said system comprising:

means for accessing an nth segment of a digital media asset having a plurality of segments;

means for decrypting at least the nth segment of the digital media asset with a decryption key;

means for decoding the decrypted nth segment to obtain decoded media data;

means for outputting the decoded media data pertaining to the decrypted nth segment to an output device;

means for determining a sequential key for a n+1th segment of the digital media asset based on at least a portion of the decoded media data pertaining to the nth segment;

means for accessing the n+1th segment of the digital media asset; and

means for decrypting the n+1th segment of the digital media asset based on at least the sequential key.

16. A system as recited in claim 15, wherein said system further comprises:

means for decoding the decrypted next segment to obtain decoded next media data; and

means for outputting the decoded next media data pertaining to the decrypted next segment to the output device.

17. A system as recited in claim 15, wherein said system further comprises:

means for accessing decryption instructions associated with the digital media asset.