System And Method For Decryption Of Content Including Disconnected Encryption Chains

• US 20130129079A1
• Filed: 05/27/2011
• Published: 05/23/2013
• Est. Priority Date: 05/27/2011
• Status: Active Grant

• Current Assignee: Adobe Inc.
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Swaminathan, Viswanathan, Mitra, Saayan
• Granted Patent: US 8,687,809 B2
• Time in Patent Office: Days
• US Class Current: 380/28
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/06 the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
• CPC Class Codes: H04L 9/0637 Modes of operation, e.g. cipher block chaining [CBC], electronic codebook [ECB] or Galois/counter mode [GCM]
• CPC Class Codes: H04L 9/50 using hash chains, e.g. blockchains or hash trees

Abstract

Embodiments may include receiving a protected version of content including different encryption chains including encrypted blocks of content. The protected version of content may include decryption information for decrypting the encrypted chains; the decryption information may include initialization vectors that are distinct from the content. Embodiments may also include performing chained decryption on a particular sequence of data blocks including multiple encryption chains from the protected version of the content and at least some of the initialization vectors. Some of the initialization vectors may be positioned between the encryption chains within the particular sequence such that during the chained decryption the initialization vectors are decrypted in sequence with the data blocks of the encryption chains. The chained decryption may result in a sequence of decrypted data blocks including decrypted initialization vectors. Embodiments may include generating a decrypted version of the content by excluding the decrypted initialization vectors from that sequence.

Claims

1. A computer-implemented method, comprising:

receiving a protected version of content that comprises different encryption chains each including encrypted blocks of content, wherein the protected version of content also includes decryption information for decrypting the encrypted chains, the decryption information including at least some initialization vectors that are distinct from the content;

performing chained decryption on a particular sequence of data blocks including multiple encryption chains from the protected version of the content and at least some of the initialization vectors, wherein said at least some of the initialization vectors are positioned between the encryption chains within the particular sequence such that during the chained decryption the initialization vectors are decrypted in sequence with the data blocks of the encryption chains, the chained decryption resulting in a sequence of decrypted data blocks including decrypted initialization vectors; and

generating a decrypted version of the content by excluding the decrypted initialization vectors from the sequence of decrypted data blocks.

2. The computer-implemented method of claim 1, wherein the protected version of content comprises one or more unencrypted data blocks representing content, wherein said chained decryption is not performed on said one or more unencrypted data blocks.

3. The computer-implemented method of claim 2, wherein said generating the decrypted version of the protected content further comprises inserting the one or more unencrypted data blocks into the sequence of decrypted data blocks.

4. The computer-implemented method of claim 1, wherein the content includes information representing one or more of audio and video.

5. The computer-implemented method of claim 1, wherein performing said chained decryption on the particular sequence of blocks comprises decrypting each of said multiple blocks with a block cipher and a cryptographic key.

6. The computer-implemented method of claim 5, wherein to perform said chained decryption on the particular sequence of blocks comprises:

using the block cipher to decrypt a first block of the particular sequence with the cryptographic key and an initialization vector from the decryption information of the protected version of the content; and

using the block cipher to decrypt each subsequent block in the sequence with the cryptographic key and an initialization vector that is equal to the previous encrypted block in the particular sequence.

7. A system, comprising:

a memory; and

one or more processors coupled to the memory, wherein the memory comprises program instructions executable by the one or more processors to;

receive a protected version of content that comprises different encryption chains each including encrypted blocks of content, wherein the protected version of content also includes decryption information for decrypting the encrypted chains, the decryption information including at least some initialization vectors that are distinct from the content;

perform chained decryption on a particular sequence of data blocks including multiple encryption chains from the protected version of the content and at least some of the initialization vectors, wherein said at least some of the initialization vectors are positioned between the encryption chains within the particular sequence such that during the chained decryption the initialization vectors are decrypted in sequence with the data blocks of the encryption chains, the chained decryption resulting in a sequence of decrypted data blocks including decrypted initialization vectors; and

generate a decrypted version of the content by excluding the decrypted initialization vectors from the sequence of decrypted data blocks.

8. The system of claim 7, wherein the protected version of content comprises one or more unencrypted data blocks representing content, wherein said chained decryption is not performed on said one or more unencrypted data blocks.

9. The system of claim 8, wherein to generate the decrypted version of the protected content the program instructions are configured to insert the one or more unencrypted data blocks into the sequence of decrypted data blocks.

10. The system of claim 7, wherein the content includes information representing one or more of audio and video.

11. The system of claim 7, wherein to perform said chained decryption on the particular sequence of blocks the program instructions are configured to decrypt each of said multiple blocks with a block cipher and a cryptographic key.

12. The system of claim 11, wherein to perform said chained decryption on the particular sequence of blocks, the program instructions are configured to:

use the block cipher to decrypt a first block of the particular sequence with the cryptographic key and an initialization vector from the decryption information of the protected version of the content; and

use the block cipher to decrypt each subsequent block in the sequence with the cryptographic key and an initialization vector that is equal to the previous encrypted block in the particular sequence.

13. The system of claim 7, wherein said protected version of content that comprises different encryption chains is encrypted according to AES-128 bit CBC mode.

14. A computer-readable storage medium, storing program instructions computer-executable on a computer to:

receive a protected version of content that comprises different encryption chains each including encrypted blocks of content, wherein the protected version of content also includes decryption information for decrypting the encrypted chains, the decryption information including at least some initialization vectors that are distinct from the content;

perform chained decryption on a particular sequence of data blocks including multiple encryption chains from the protected version of the content and at least some of the initialization vectors, wherein said at least some of the initialization vectors are positioned between the encryption chains within the particular sequence such that during the chained decryption the initialization vectors are decrypted in sequence with the data blocks of the encryption chains, the chained decryption resulting in a sequence of decrypted data blocks including decrypted initialization vectors; and

generate a decrypted version of the content by excluding the decrypted initialization vectors from the sequence of decrypted data blocks.

15. The computer-readable storage medium of claim 14, wherein the protected version of content comprises one or more unencrypted data blocks representing content, wherein said chained decryption is not performed on said one or more unencrypted data blocks.

16. The computer-readable storage medium of claim 15, wherein to generate the decrypted version of the protected content the program instructions are configured to insert the one or more unencrypted data blocks into the sequence of decrypted data blocks.

17. The computer-readable storage medium of claim 14, wherein the content includes information representing one or more of audio and video.

18. The computer-readable storage medium of claim 14, wherein to perform said chained decryption on the particular sequence of blocks the program instructions are configured to decrypt each of said multiple blocks with a block cipher and a cryptographic key.

19. The computer-readable storage medium of claim 18, wherein to perform said chained decryption on the particular sequence of blocks, the program instructions are configured to:

use the block cipher to decrypt a first block of the particular sequence with the cryptographic key and an initialization vector from the decryption information of the protected version of the content; and

use the block cipher to decrypt each subsequent block in the sequence with the cryptographic key and an initialization vector that is equal to the previous encrypted block in the particular sequence.

20. The computer-readable storage medium of claim 14, wherein said protected version of content that comprises different encryption chains is encrypted according to AES-128 bit CBC mode.