Method and a device for encryption of images

• US 6,931,534 B1
• Filed: 11/19/1999
• Issued: 08/16/2005
• Est. Priority Date: 11/20/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Larsson, Mathias, Jändel, Magnus
• Primary Examiner(s): Morse, Gregory
• Assistant Examiner(s): Baum, Ronald
• Application Number:
  US09/443,813
• Time in Patent Office: 2,097 Days
• Field of Search: 380/54, 380200-203, 380210-217, 713/176, 713/180, 713/160
• US Class Current: 713/176
• CPC Class Codes: H04N 1/32776 using an interactive, user-operated device, e.g. a computer terminal, mobile telephone H04N1/32782, H04N1/32784 take precedence
• CPC Class Codes: H04N 1/4486 using digital data encryption
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object

Abstract

In a method and a device for partial encryption and progressive transmission of images, a first section of the image file is compressed at reduced quality without decryption, and a second section of the image file is encrypted. Users having access to appropriate decryption keywords can decrypt this second section. The first section together with the decrypted second section can then be viewed as a full quality image. The storage space required for storing the first and section together is essentially the same as the storage space required for storing the unencrypted full quality image. By using the method and device as described herein storage and bandwidth requirements for partially encrypted images is reduced. Furthermore, object based composition and processing of encrypted objects are facilitated, and ROIs can be encrypted. Also, the shape of a ROI can be encrypted and the original object can be decrypted and restored in the compressed domain.

Claims

1. A method of decoding image data of an image comprising the steps of:

receiving an image bit stream comprising header information and independently decodable coding units of said image, said header information identifying first image data of said image as not encrypted and second image data of said image as encrypted;

decoding all of at least one independently decodable coding unit of said first image data identified by said header information as not encrypted;

sending a request for a decryption key for decrypting at least one independently decodable coding unit of said second image data identified by said header information as encrypted;

receiving a decryption key upon said request;

decrypting the at least one independently decodable coding unit of said second image data with said received decryption key.

3. A method according to claim 1 comprising the further step of:

receiving condition information that includes a cost for decrypting at least one independently decodable coding unit of said second image data identified by said header information in said image bit stream as encrypted.

4. A method according to claim 1, wherein the first image data identified by said header information in said image bit stream as not encrypted corresponds to a low resolution version of said image.

5. A method according to claim 1, wherein different independently decodable coding units are decoded using different decoding methods.

6. A method according to claim 1, wherein said header information in said image bit stream comprises an encryption flag identifying image data as encrypted first image data or as not encrypted second image data.

7. A method according to claim 6, wherein said encryption flag identifies an individual independently decodable coding unit of said image as encrypted first image data or as not encrypted second image data.

8. A method according to claim 1, wherein said second image data identified in said image bit stream as encrypted constitutes a region of interest in a cloaking shape.

9. A method according to claim 8, wherein said cloaking shape is a bounding box.

10. A method according to claim 1, further comprising:

using the at least one independently decodable coding unit of said first image data to obtain a partial resolution version of the image;

then

obtaining a decryption key for decrypting at least one independently decodable coding unit of said second image data; and

using the at least one independently decodable coding unit of said second image data to obtain a higher resolution version of the image than the partial resolution version.

2. A method of decoding image data of an image comprising the steps of:

receiving an image bit stream comprising header information and independently decodable coding units of said image, said header information identifying first image data of said image as not encrypted and second image data of said image as encrypted;

decoding all of at least one independently decodable coding unit of said first image data identified by said header information as not encrypted;

sending a request for a decryption key for decrypting at least one independently decodable coding unit of said second image data identified by said header information as encrypted;

receiving a decryption key upon said request;

receiving upon said request at least one independently decodable coding unit of said second image data;

decrypting said at least one upon said request received independently decodable coding unit of said second image data with said received decryption key.

11. A device for decoding image data of an image comprising:

means for receiving an image bit stream of header information and independently decodable coding units of said image, said header information identifying first image data of said image as not encrypted and second image data of said image as encrypted;

means for decoding all of at least one independently decodable coding unit of said first image data identified by said header information as not encrypted;

means for sending a request for a decryption key for decrypting at least one independently decodable coding unit of said second image data identified by said header information as encrypted;

means for receiving a decryption key upon said request; and

means for decrypting at least one independently decodable coding unit of said second image data with said received decryption key.

13. A device according to claim 11, further comprising:

means for receiving condition information that includes a cost for decrypting at least one independently decodable coding unit of said second image data identified by said header information in said image bit stream as encrypted.

14. A device according to claim 11, further comprising means for decoding different independently decodable coding units using different decoding methods.

19. A device according to claim 11, further comprising:

means for using the at least one independently decodable coding unit of said first image data to obtain a partial resolution version of the image;

then

means for obtaining a decryption key for decrypting at least one independently decodable coding unit of said second image data; and

means for using the at least one independently decodable coding unit of said second image data to obtain a higher resolution version of the image than the partial resolution version.

12. A device for decoding image data of an image comprising:

means for receiving an image bit stream of header information and independently decodable coding units of said image, said header information identifying first image data of said image as not encrypted and second image data of said image as encrypted;

means for decoding all of at least one independently decodable coding unit of said first image data identified by said header information as not encrypted;

means for sending a request for a decryption key for decrypting at least one independently decodable coding unit of said second image data identified by said header information as encrypted;

means for receiving a decryption key upon said request; and

means for receiving upon said request at least one independently decodable coding unit of said second image data;

means for decrypting said at least one received independently decodable coding unit of said second image data with said received decryption key.

15. A device for encoding image data of an image comprising:

means for sending encoded image data of said image in a bit stream;

means for inserting header information in said image data bit stream, said header information identifying first image data as not encrypted, said header information identifying second image data as encrypted;

means for sending condition information that includes a cost for decrypting second image data of said image;

means for receiving a request for a decryption key for decrypting second image data of said image;

means for sending a decryption key for decrypting the second image data of said image.

16. A device according to claim 15, further comprising:

means for sending encrypted second image data of said image upon said request.

17. A device according to claim 15, further comprising:

means for inserting an encryption flag as header information for identifying image data of said image as not encrypted first image data or as encrypted second image data.

18. A device according to claim 15, further comprising:

means for inserting an encryption flag as header information for identifying an individual independently decodable coding unit of said image as not encrypted first image data or as encrypted second image data.