MPEG-4 ENCRYPTION ENABLING TRANSCODING WITHOUT DECRYPTION

• US 20060282665A1
• Filed: 05/19/2006
• Published: 12/14/2006
• Est. Priority Date: 05/20/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Zhu, Bin, Li, Shipeng, Yang, Yang, Chen, Chang Wen
• Granted Patent: US 7,953,224 B2
• Time in Patent Office: Days
• US Class Current: 713/160
• CPC Class Codes: H04N 19/20 using video object coding
• CPC Class Codes: H04N 19/34 Scalability techniques involving progressive bit-plane based encoding of the enhancement layer, e.g. fine granular scalability [FGS]
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• CPC Class Codes: H04N 21/8451 using Advanced Video Coding [AVC]
• 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

A method and system for encrypting a video compressed with MPEG-4 FGS compression with minimal overhead is provided. The encryption system encrypts the video into independently encrypted segments that can be either a video packet or a video block. When the encryption system encrypts based on video packets, it encrypts the data to ensure that the encrypted data does not emulate any video packet delimiting markers. When the encryption system encrypts based on video blocks, it encrypts the coded bitstream for each video block independently, from the most significant bitplane to the least significant bitplane, using either a stream or a block cipher. After all the video blocks are independently encrypted, the encryption system partitions the encrypted data into video packets and adds a buffering bit, if necessary, to prevent emulation of video packet delimiting markers. The encryption system may generate an initialization vector for each independently encrypted segment.

Claims

1. A method for encrypting a video, the method comprising:

identifying independent encryption segments of the video; and

for each identified independent encryption segment,

generating an initialization vector for the independent encryption segment; and

encrypting data of the independent encryption segment using the generated initialization vector.

2. The method of claim 1 wherein an independent encryption segment is a video packet of MPEG-4 Fine Grain Scalability compression.

3. The method of claim 1 wherein an independent encryption segment is a video block of MPEG-4 Fine Grain Scalability compression.

4. The method of claim 1 wherein the encrypting of an independent encryption segment applies an encryption scheme that generates syntax-compliant ciphertext.

5. The method of claim 4 wherein the encryption scheme is a locally iterative encryption scheme.

6. The method of claim 5 wherein the locally iterative encryption scheme in cipher block chaining mode is applied to full encryption blocks and the locally iterative encryption scheme in cipher feedback mode is applied to a last partial encryption block.

7. The method of claim 4 wherein the encryption scheme is a ciphertext switching scheme.

8. The method of claim 1 wherein the initialization vector for an independent encryption segment is generated from an initialization vector of the video and a unique identifier of the independent encryption segment.

9. The method of claim 8 wherein the unique identifier for a video block is a VOP-specific number, a video block number, and an identifier of a color component.

10. The method of claim 8 wherein the unique identifier for a video packet is a VOP-specific number, a number of the first macroblock, and a bitplane identifier.

11. The method of claim 1 wherein buffering bits are added to encrypted data to stop emulation of delimiting markers.

12. A system for encrypting video data, comprising:

a component that identifies segments of the video data;

a component that encrypts each segment so that the encrypted data in each segment does not include any delimiters of a video packet; and

a component that packetizes the encrypted segments into an encrypted video codestream.

13. The system of claim 12 wherein a segment is a video block and encrypted data from multiple video blocks are stored in a video packet.

14. The system of claim 12 wherein a segment is a video packet.

15. The system of claim 14 wherein when the segment is a video packet, the component that encrypts applies a locally iterative encryption scheme.

16. The system of claim 14 wherein when the segment is a video packet, the component that encrypts applies a ciphertext switching scheme.

17. The system of claim 12 wherein the component for encrypting

generates an initialization vector from a global initialization vector and a unique identifier of an independent encryption segment;

and

encrypts the independent encryption segment using the generated initialization vector.

18. The system of claim 12 wherein the packetizing component adds buffering bits to stop emulation of delimiter markers in encrypted data.

19. A computer-readable medium containing encryption of video data that is compressed using an MPEG-4 FGS based compression, the encryption being generated by a method comprising:

identifying independent encryption segments from the video data; and

for each identified independent encryption segment,

providing an initialization vector for the independent encryption segment;

encrypting the video data in the independent encryption segment using the provided initialization vector to generate ciphertext; and

packetizing encrypted segments into an encrypted codestream without emulation of delimiting markers in the encrypted data.

20. The computer-readable medium of claim 19 wherein the initialization vector for an independent encryption segment is provided based on a global initialization vector and a unique identifier of the segment.