Watermark With Data Integrity Verification

• US 20150200773A1
• Filed: 01/13/2014
• Published: 07/16/2015
• Est. Priority Date: 01/13/2014
• Status: Active Grant

• Current Assignee: Synamedia Limited
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Sella, Yaron, CAIN, Harel, DEVIR, Michal
• Granted Patent: US 9,137,010 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04L 2209/24 Key scheduling, i.e. generating round keys or sub-keys for block encryption
• CPC Class Codes: H04L 2209/30 Compression, e.g. Merkle-Damgard construction
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/0816 Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation
• CPC Class Codes: H04N 2201/3281 Encryption; Ciphering
• CPC Class Codes: H04N 2201/3284 for error correction

Abstract

In one embodiment, a system including a processor is operative to receive a content item including a watermark encoding a series of encrypted bits deriving from encrypting an information element multiple times, extract at least some encrypted bits from at least part of the watermark, decrypt a series of N bits using a first key yielding a first value, the series of N bits including Q bits of the encrypted bits and K, greater than, or equal to zero, guessed bits, re-encrypt the first value using a second key yielding a second value, and compare at least part of the second value to M bits of the encrypted bits to determine if at least part of the second value matches the M bits in order to provide a level of confidence that the first value is the information element which was encrypted and embedded as the watermark.

Claims

1. A system comprising:

a processor; and

a memory to store data used by the processor, wherein the processor is operative to;

receive a media content item including a watermark embedded in the media content item, the watermark encoding a series of encrypted bits deriving from encrypting an information element multiple times with a plurality of cryptographic keys such that each of the times the encryption of the information element uses a different one of the cryptographic keys yielding a plurality of encrypted instances of the information element in the series of encrypted bits, the order of the cryptographic keys used in the series of encrypted bits being defined such that an i^th encrypted instance of the information element in the series of encrypted bits being encrypted with an i^th one of the cryptographic keys K_i, the information element consisting of N bits;

identify at least part of the watermark in the media content item;

extract at least some of the encrypted bits from the at least part of the identified watermark;

decrypt a series of N bits using a first one of the cryptographic keys yielding a first value, the series of N bits including Q bits of the encrypted bits as ordered in the series of the encrypted bits and K guessed bits, K being greater than, or equal to, zero, K plus Q equaling N;

re-encrypt the first value using a second one of the cryptographic keys yielding a second value, the second cryptographic key being different from the first cryptographic key; and

compare at least part of the second value to M bits of the encrypted bits as ordered in the series of the encrypted bits to determine if the at least part of the second value matches the M bits as ordered in the series of the encrypted bits in order to provide a level of confidence that the first value is indeed the information element which was encrypted and embedded as the watermark in the media content item, the Q bits and the M bits being selected from different bits of the encrypted bits, M being greater than zero.

2. The system according to claim 1, wherein:

the first cryptographic key is a j^th one of the cryptographic keys;

j is an integer;

the M bits and the Q bits are positioned in the series of encrypted bits in adjacent encrypted instances of the information element; and

the second cryptographic key is a j+1^th or a j−

1^th one of the cryptographic keys.

3. The system according to claim 2, wherein:

the media content stream does not indicate which of the cryptographic keys were used to encrypt the encrypted instances of the information element; and

the processor is operative, via a process of trial and error, to perform the decryption of the series of N bits and the re-encryption of the first value and the comparison of the at least part of the second value to the M bits using different values of j until it is determined that the at least part of the second value matches the M bits as ordered in the series of the encrypted bits.

4. The system according to claim 1, wherein:

the media content stream does not indicate which of the cryptographic keys were used to encrypt the encrypted instances of the information element; and

the processor is operative, via a process of trial and error to perform the decryption of the series of N bits and the re-encryption of the first value and the comparison of the at least part of the second value to the M bits using different combinations of the cryptographic keys until it is determined that at least part of the second value matches the M bits as ordered in the series of the encrypted bits.

5. The system according to claim 1, wherein the watermark includes at least one indicator to indicate positioning of each of the encrypted instances of the information element within the watermark and which ones of the cryptographic keys were used to encrypt each of the encrypted instances.

6. The system according to claim 1, wherein the processor is operative to:

re-encrypt the first value using a third one of the cryptographic keys yielding a third value, the third cryptographic key being different from the first cryptographic key and the second cryptographic key; and

compare the at least part of the third value to P bits of the encrypted bits as ordered in the series of the encrypted bits to determine if the at least part of the third value matches the P bits as ordered in the series of the encrypted bits in order to provide a further level of confidence that the first value is the information element which was encrypted and embedded as the watermark in the media content item, the Q bits and the M bits and the P bits being selected from different bits of the encrypted bits, the M bits and the P bits corresponding to different parts of the information element.

7. The system according to claim 6, wherein M plus P is equal to N.

8. The system according to claim 6, wherein M plus P is less than N.

9. The system according to claim 6, wherein:

the first cryptographic key is a j^th one of the cryptographic keys;

j is a integer;

the M bits and the P bits are positioned in encrypted instances of the information element which are either side of one of the encrypted instances of the information element which includes the Q bits;

the second cryptographic key is a j+1^th one of the cryptographic keys; and

the third cryptographic key is a j−

1^th one of the cryptographic keys.

10. The system according to claim 9, wherein:

the media content stream does not indicate which of the cryptographic keys were used to encrypt the encrypted instances of the information element; and

the processor is operative, via a process of trial and error, to perform the decryption of the first N bits and the re-encryption of the first value and the comparison of the at least part of the second value to the M bits and the at least part of the third value to the P bits using different values of j until it is determined that the at least part of the second value matches the M bits as ordered in the series of the encrypted bits and that the at least part of the third value matches the P bits as ordered in the series of the encrypted bits.

11. The system according to claim 6, wherein:

the media content stream does not indicate which of the cryptographic keys were used to encrypt the encrypted instances of the information element; and

the processor is operative, via a process of trial and error, to perform the decryption of the first N bits and the re-encryption of the first value and the comparison of the at least part of the second value to the M bits and the at least part of the third value to the P bits using different combinations of the cryptographic keys until it is determined that the at least part of the second value matches the M bits as ordered in the series of the encrypted bits and that the at least part of the third value matches the P bits as ordered in the series of the encrypted bits.

12. The system according to claim 1, wherein:

the position of the encrypted instances of the information element in the at least some encrypted bits extracted from the at least part of the identified watermark is unknown; and

the processor is operative, by a process of trial and error, to perform the decryption of the series of N bits and the re-encryption of the first value and the comparison of the at least part of the second value to the M bits based on different positions of the series of N bits and the M bits within the series of encrypted bits until it is determined that the at least part of the second value matches the M bits as ordered in the series of the encrypted bits.

13. The system according to claim 1, wherein:

the series of encrypted bits derives from encrypting the information element multiple times, some of the times the information element is first processed by a first cryptographic function using a secret key as input yielding a secondary information element, each of the some times the secondary information element is then processed by a second cryptographic function using a different one of the cryptographic keys as input; and

the decryption of the series of N bits includes processing the series of N bits by a third cryptographic function using the first cryptographic key as input yielding an output and then processing the output by a fourth cryptographic function yielding the first value, the third cryptographic function being an inverse function of the second cryptographic function, the fourth cryptographic function being an inverse function of the first cryptographic function.

14. The system according to claim 13, wherein:

the information element is publically known and the secondary information element is not publically known;

or

the information element is not publically known and the secondary information element is publically known.

15. The system according to claim 1, wherein:

the series of encrypted bits derives from encrypting the information element multiple times, some of the times the information element is first processed by a first cryptographic function using a secret key as input yielding a secondary information element, each of the some times the secondary information element is then processed by a second cryptographic function using a different one of the cryptographic keys as input; and

the re-encryption of the first value includes processing the first value by the first cryptographic function using the secret key as input yielding an output and then processing the output by a third cryptographic function yielding the second value, the third cryptographic function being an inverse function of the second cryptographic function.

16. The system according to claim 15, wherein:

the information element is publically known and the secondary information element is not publically known;

or

the information element is not publically known and the secondary information element is publically known.

17. The system according to claim 1, wherein each of the cryptographic keys comprises a corresponding encryption key and decryption key to enable asymmetric encryption/decryption.

18. The system according to claim 1, wherein each of the cryptographic keys is a symmetric cryptographic key used in both encryption and decryption.

19. A method comprising:

receiving a media content item including a watermark embedded in the media content item, the watermark encoding a series of encrypted bits deriving from encrypting an information element multiple times with a plurality of cryptographic keys such that each of the times the encryption of the information element uses a different one of the cryptographic keys yielding a plurality of encrypted instances of the information element in the series of encrypted bits, the order of the cryptographic keys used in the series of encrypted bits being defined such that an i^th encrypted instance of the information element in the series of encrypted bits being encrypted with an i^th one of the cryptographic keys K_i, the information element consisting of N bits;

identifying at least part of the watermark in the media content item;

extracting at least some of the encrypted bits from the at least part of the identified watermark;

decrypting a series of N bits using a first one of the cryptographic keys yielding a first value, the series of N bits including Q bits of the encrypted bits as ordered in the series of the encrypted bits and K guessed bits, K being greater than, or equal to, zero, K plus Q equaling N;

re-encrypting the first value using a second one of the cryptographic keys yielding a second value, the second cryptographic key being different from the first cryptographic key; and

comparing at least part of the second value to M bits of the encrypted bits as ordered in the series of the encrypted bits to determine if the at least part of the second value matches the M bits as ordered in the series of the encrypted bits in order to provide a level of confidence that the first value is indeed the information element which was encrypted and embedded as the watermark in the media content item, the Q bits and the M bits being selected from different bits of the encrypted bits, M being greater than zero.

20. A system comprising:

a processor; and

a memory to store data used by the processor, wherein the processor is operative to;

receive a media content item including a watermark embedded in the media content item, the watermark encoding a series of encrypted bits, the encrypted bits deriving from encrypting an information element multiple times with a plurality of cryptographic keys such that each of the times the information element is encrypted with a different one of the cryptographic keys yielding a plurality of encrypted instances of the information element in the series of encrypted bits, the order of the cryptographic keys used in the series of encrypted bits being defined such that an i^th encrypted instance of the information element in the series of encrypted bits being encrypted with an i^th one of the cryptographic keys K_i;

identify at least part of the watermark in the media content item;

extract at least some of the encrypted bits from the at least part of the identified watermark;

decrypt one of the encrypted instances of the information element using a first one of the cryptographic keys yielding a first value;

decrypt a different one of the encrypted instances of the information element using a second one of the cryptographic keys yielding a second value, the second cryptographic key being different from the first cryptographic key; and

compare the first value and the second value to determine if the first value matches the second value in order to provide a level of confidence that the first value is indeed the information element which was encrypted and embedded as the watermark in the media content item.