IMAGE ENCRYPTING DEVICE, IMAGE DECRYPTING DEVICE AND METHOD

• US 20100067706A1
• Filed: 11/23/2009
• Published: 03/18/2010
• Est. Priority Date: 05/30/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kuraki, Kensuke, Anan, Taizo, Nakagata, Shohei
• Granted Patent: US 8,571,212 B2
• Time in Patent Office: Days
• US Class Current: 380/285
• CPC Class Codes: G06F 21/608 Secure printing
• CPC Class Codes: G09C 5/00 Ciphering apparatus or methods not provided for in the preceding groups, e.g. involving the concealment or deformation of graphic data such as designs, written or printed messages
• CPC Class Codes: H04L 2209/88 Medical equipments
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04N 1/4486 using digital data encryption

Abstract

An encrypting device generates an encrypted image by converting an image of a specified region in an input image with an encryption key, by embedding information obtained by encrypting the encryption key with a public key pairing with the private key of a destination, and by performing pixel value conversion. Then, the encrypted image is transmitted to the destination as a printed matter or via a network. A decrypting device converts the encrypted image in the form of print data or electronic data into an image, and inputs it. Next, the decrypting device extracts a decryption key (the encryption key) from the image of the encryption region by executing a process reverse to that of the encrypting device for the encryption region of the converted encrypted image. Then, the decrypting device decrypts the original image of the encrypted region by using the decryption key, and restores the entire encrypted image.

Claims

1. An image encrypting device for encrypting an image, comprising:

input means for inputting image data to be encrypted;

encryption region specifying means for specifying a region to be encrypted in the image data input by the input means;

image converting means for converting the encryption region, which is specified by the encryption region specifying means, into a first image by using an encryption key;

public key obtaining means for obtaining a public key of a transmission destination of the data to be encrypted;

key encrypting means for encrypting the encryption key by using the public key obtained by the public key obtaining means;

information embedding means for embedding encryption key associated information, which is information about the encryption key encrypted by the key encrypting means, in the first image to convert the encryption region into a second image;

pixel value converting means for converting a pixel value of the second image to convert the encryption region into a third image so that the region specified by the encryption region specifying means is identifiable; and

output means for outputting an encrypted image, which is obtained by converting an image of the encryption region into the third image in the image input by the input means, in a predetermined method.

2. The image encrypting device according to claim 1, wherein:

the encryption region specifying means specifies a plurality of encryption regions;

the image converting means converts images of the plurality of encryption regions individually by using a plurality of encryption keys;

the public key obtaining means obtains a plurality of public keys; and

the key encrypting means encrypts the plurality of encryption keys, which the image converting means uses to convert the images of the plurality of encryption regions, individually by using the plurality of public keys obtained by the public key obtaining means.

3. The image encrypting device according to claim 2, wherein

the plurality of public keys obtained by the public key obtaining means is public keys of a plurality of transmission destinations.

4. The image encrypting device according to claim 1 wherein

the key encrypting means encrypts the encryption key by using the public key, and a private key of another party to which the transmission destination submits the encrypted image.

5. The image encrypting device according to claims 1, wherein

the public key obtaining means obtains the public key from a public key management server that manages the public key.

6. An image decrypting device for decrypting an encrypted image including an image encrypted into an original image, comprising:

input means for inputting the encrypted image as image data;

encryption position detecting means for detecting a position of an encryption region that is a region, in which an image is encrypted in the encrypted image, by analyzing the encrypted image input by the input means;

pixel value converting means for restoring a pixel value of the image of the encryption region to a pixel value before being converted in order to identify the position of the encryption region on the basis of information about the position of the encryption region detected by the encryption position detecting means;

information extracting means for extracting encryption key associated information, which is information about an encryption key embedded in the image of the encryption region, from the image of the encryption region, which is generated by the pixel value converting means;

key decrypting means for decrypting a decryption key, which is used to decrypt the image of the encryption region, from the encryption key associated information by using a first private key pairing with a first public key used to generate the encryption key associated information extracted by the information extracting means;

image converting means for decrypting an original image by decrypting the image of the encryption region by using the decryption key decrypted by the key decrypting means; and

output means for outputting the original image in a predetermined method.

7. The image decrypting device according to claim 6, wherein

the first private key is a private key that is possessed by a transmission destination of the encrypted image and pairs with a second public key used by another party, to which the transmission destination submits the encrypted image, to decrypt the encrypted image.

8. The image decrypting device according to claim 6 further comprising

public key obtaining means for obtaining a public key to obtain the second public key pairing with a second private key, if the encryption key associated information is encrypted with the first public key and the second private key, wherein

the key encrypting means decrypts the decryption key from the encryption key associated information by using the first private key and the second public key.

9. The image decrypting device according to claim 6, wherein:

each piece of encryption key associated information, which is included in an image of each of a plurality of encryption regions, is information about an individual encryption key;

the information extracting means extracts an individual piece of the encryption key associated information from each of the plurality of encryption regions; and

the key decrypting means decrypts, from each piece of the encryption key associated information extracted by the information extracting means, each decryption key used to decrypt the image of each of the plurality of encryption regions, in which each piece of the encryption key associated information is embedded, by using a public key pairing with a private key used to generate each piece of the encryption key associated information.

10. The image decrypting device according to claims 6, wherein

the public key obtaining means obtains the public key from a public key management server that manages the public key.

11. An image encrypting method for encrypting an image, comprising:

a step of inputting image data to be encrypted;

a step of specifying a region to be encrypted in the image data input by the input step;

a step of converting the specified encryption region into a first image by using an encryption key;

a step of obtaining a public key of a transmission destination of the data to be encrypted;

a step of encrypting the encryption key by using the obtained public key;

a step of embedding encryption key associated information, which is information about the encrypted encryption key, in the first image to convert the encryption region into a second image;

a step of converting a pixel value of the second image to convert the encryption region into a third image so that the region specified to be encrypted is identifiable; and

a step of outputting an encrypted image, which is obtained by converting an image of the encryption region into the third image in the input image to be encrypted, in a predetermined method.

12. The image encrypting method according to claim 11, wherein:

the encryption region specifying step specifies a plurality of encryption regions;

the image converting step converts image of the plurality of encryption regions individually by using a plurality of encryption keys;

the public key obtaining step obtains a plurality of public keys; and

the key encrypting step encrypts the plurality of encryption keys, which are used to convert the images of the plurality of encryption regions, individually by using the plurality of public keys, which are obtained by the public key obtaining step.

13. The image encrypting method according to claim 11, wherein

the plurality of public keys obtained by the public key obtaining step are public keys of a plurality of transmission destinations.

14. An image decrypting method for decrypting an encrypted image including an image encrypted into an original image, comprising:

a step of inputting the encrypted image as image data;

a step of detecting a position of an encryption region that is a region, in which an image is encrypted in the encrypted image, by analyzing the encrypted image input by the input step;

a step of restoring a pixel value of the image of the encryption region to a pixel value before being converted in order to identify the position of the encryption region on the basis of information about the detected position of the encryption region;

a step of extracting encryption key associated information, which is information about an encryption key embedded in the image of the encryption region, from the image of the encryption region generated by the pixel value converting step;

a step of decrypting a decryption key, which is used to decrypt the image of the encryption region, from the encryption key associated information by using a first private key pairing with a first public key used to generate the extracted encryption key associated information;

a step of decrypting the original image by decrypting the image of the encryption region by using the decrypted decryption key; and

a step of outputting the original image in a predetermined method.

15. The image decrypting method according to claim 14, wherein

the first private key is a private key that is possessed by a transmission destination of the encrypted image and pairs with a second public key used by another party, to which the transmission destination submits the encrypted image, to decrypt the encrypted image.

16. The image decrypting method according to claim 14, further comprising

a step of obtaining a public key to obtain the second public key pairing with a second private key, if the encryption key associated information is encrypted by using the first public key and the second private key, wherein

the key encrypting step decrypts the decryption key from the encryption key associated information by using the first private key and the second public key.

17. The image decrypting method according to claim 14, wherein:

each piece of encryption key associated information, which is included in an image of each of a plurality of encryption regions, is information about an individual encryption key;

the information extracting step extracts an individual piece of the encryption key associated information from each of the plurality of encryption regions; and

the key decrypting step decrypts each decryption key used to decrypt the image of each of the plurality of encryption regions, in which each piece of the encryption key associated information is embedded, is decrypted by using a public key pairing with a private key, which is used to generate each piece of the encryption key associated information, from each piece of the encryption key associated information, which is extracted in the information extracting step.

18. A storage medium storing an image encrypting program for causing a computer, in order to encrypt an image, to operate as:

input means for inputting image data to be encrypted;

encryption region specifying means for specifying a region to be encrypted in the image input by the input means;

image converting means for converting the encryption region specified by the encryption region specifying means into a first image by using an encryption key;

public key obtaining means for obtaining a public key of a transmission destination of the data to be encrypted;

key encrypting means for encrypting the encryption key by using the public key obtained by the public key obtaining means;

information embedding means for embedding encryption key associated information, which is information about the encryption key encrypted by the key encrypting means, in the first image to convert the encryption region into a second image;

pixel value converting means for converting a pixel value of the second image to convert the encryption region into a third image so that the region specified by the encryption region specifying means is identifiable; and

output means for outputting an encrypted image, which is obtained by converting an image of the encryption region into the third image in the image input by the input means, in a predetermined method.

19. The storage medium according to claim 18, wherein:

the encryption region specifying means specifies a plurality of encryption regions;

the image converting means converts images of the plurality of encryption regions individually by using a plurality of encryption keys;

the public key obtaining means obtains a plurality of public keys; and

the key encrypting means encrypts the plurality of encryption keys, which the image converting means uses to convert the images of the plurality of encryption regions, individually by using the plurality of public keys obtained by the public key obtaining means.

20. The storage medium according to claim 19, wherein

the image converting means individually converts an image in each of the plurality of encryption regions by using an individual encryption key.

21. The storage medium according to claim 19, wherein

the plurality of public keys obtained by the public key obtaining means are public keys of a plurality of transmission destinations.

22. A storage medium storing an image decrypting program for causing a computer, in order to decrypt an encrypted image including an image encrypted into an original image, to operate as:

input means for inputting the encrypted image as image data;

encryption position detecting means for detecting a position of an encryption region that is a region, in which an image is encrypted in the encrypted image, by analyzing the encrypted image input by the input means;

pixel value converting means for restoring a pixel value of an image of the encryption region to a pixel value before being converted in order to identify the position of the encryption region on the basis of information about the position of the encryption region detected by the encryption position detecting means;

information extracting means for extracting encryption key associated information, which is information about an encryption key embedded in the image of the encryption region, from the image of the encryption region generated by the pixel value converting means;

key decrypting means for decrypting a decryption key, which is used to decrypt the image of the encryption region, from the encryption key associated information by using a first private key pairing with a first public key used to generate the encryption key associated information extracted by the information extracting means;

image converting means for decrypting the original image by decrypting the image of the encryption region by using the decryption key decrypted by the key decrypting means; and

means for outputting the original image in a predetermined method.

23. The storage medium according to claim 22, wherein

the first private key is a private key that is possessed by a transmission destination of the encrypted image and pairs with a second public key used by another party, to which the transmission destination submits the encrypted image, to decrypt the encrypted image.

24. The storage medium according to claim 22, the image decrypting program causing the computer to further operate as

public key obtaining means for obtaining a public key to obtain the second public key pairing with a second private key, if the encryption key associated information is encrypted with the first public key and the second private key, wherein

the key encrypting means decrypts the decryption key from the encryption key associated information by using the first private key and the second public key.

25. The storage medium according to claim 22, wherein:

each piece of encryption key associated information, which is included in an image of each of the plurality of encryption regions, is information about an individual encryption key;

the information extracting means extracts an individual piece of the encryption key associated information from each of the plurality of encryption regions; and

the key decrypting means decrypts, from each piece of the encryption key associated information extracted by the information extracting means, each decryption key used to decrypt the image of each of the plurality of encryption regions, in which each piece of the encryption key associated information is embedded, by using a public key pairing with the private key used to generate each piece of the encryption key associated information.