JP2000066593A - Encryption apparatus, encryption method, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make forgery and cryptoanalysis by inference, etc., difficult by embedding an authentication code to authenticate the person himself or herself into a digital image and subjecting the entire part of the digital image to encryption. SOLUTION: Digest data is prepared by subjecting the digital image data over the entire part including the authentication data and other image data to encryption. Unidirectional functions can be used for the encryption. The formed digest data an further encrypted by a receiver's password, etc., to prepare the encrypted digest data. The encrypted digest data are recorded into the original region, thereby, a hardly forgeable digital card including the authentication code and the encrypted digest data in a part of the original image data can be prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an encryption device, an encryption method, and a recording medium.

[0002]

2. Description of the Related Art Conventionally, protocols such as SSL (Secure Sockets Layer) or personal authentication methods such as digital signatures or digital certificates have been developed to prevent information tampering and identity impersonation on networks such as the Internet. ing. Generally, a digital certificate is obtained by encrypting a text data document that proves the identity of a person, and sends the digital certificate to a recipient together with data to be sent to the recipient.

[0003] However, since the above-mentioned digital certificate is a document, there has been a problem that the forgery of the certificate itself is easy by analogy or the like, and the decryption of the encrypted document is relatively easy.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problem. An authenticator for authenticating a person is embedded in a digital image, and the entire digital image is encrypted. Accordingly, an object of the present invention is to provide an encryption device, an encryption method, and a recording medium that are difficult to forge and decipher by analogy or the like.

[0005]

According to the first aspect of the present invention,
An encryption device for encrypting and embedding an authenticator in a part of digital image data, comprising: authentication data recording means for recording authentication data including the authenticator instead of a part of the digital image data; Encrypting means for encrypting the entire digital image data on which the authentication data is recorded by a recording means to obtain encrypted data of a length excluding the authenticator from the authentication data; and Is recorded in a portion of the authentication data excluding the authenticator.

According to a second aspect of the present invention, in the first aspect, the authentication data recording means includes means for designating a part of the digital image data, and a predetermined bit in the designated part of the digital image data. Means for designating data corresponding to a position and means for recording the authentication data instead of the data corresponding to the designated predetermined bit position can be provided.

According to a third aspect of the present invention, in the first aspect, the encryption performed by the encryption means can be encryption performed by using a one-way function on the entire digital image data. .

According to a fourth aspect of the present invention, there is provided an encryption method for encrypting and embedding an authenticator in a part of digital image data, wherein a step of designating a part of the digital image data, Specifying data corresponding to a predetermined bit position in a part of the image data; recording authentication data including the authenticator in place of the data corresponding to the specified predetermined bit position; Encrypting the entire digital image data on which data is recorded by using a one-way function to obtain encrypted data of a length excluding the authenticator from the authentication data; and Recording the encrypted data in a portion of the authentication data excluding the authenticator.

According to a fifth aspect of the present invention, there is provided a computer-readable recording medium recording a program for executing the encryption method according to the fourth aspect.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an embodiment of the encryption method of the present invention. FIG. 1A shows an embodiment of image data targeted by the encryption apparatus or method of the present invention.
(B), (C) and (D) show an embodiment of the encryption method of the present invention in this order.

In FIG. 1A, digital image data 100 is issued by an organization or the like that has issued an image-type digital certificate (hereinafter referred to as a “digital card”) encrypted by the encryption device of the present invention. It includes institution data 102, image data 104 such as a photograph of the person, expiration date data 106 indicating the expiration date of the digital card, and other person data 108 such as the person's e-mail address. The size of the digital image data 100 is 4800 dots (4800 bytes) of 60 dots vertically by 80 dots horizontally.
However, this is merely an example for explanation, and the present invention is not limited to this size.

In FIG. 1B, an arbitrary part 110 of the digital image data 100 is designated. A part 110 of the digital image data 100 is cut out as a digital stripe of 10 dots vertically × 80 dots horizontally,
It can also be temporarily stored in a storage device (not shown) such as a register or a memory.

FIG. 1C shows a part 110 of the digital image data 100 shown in FIG. 1B, including its gradation. In the present embodiment, 8-bit 256-level gradation is exemplarily used. Therefore, corresponding to each dot of a part 110 of the digital image data 100, data 120 corresponding to the D0 bit position and corresponding to data D0 to D7 bit position. 8 bits of data 127 are shown. Generally, an image can be expressed relatively clearly if the gradation is 64 steps of 6 bits. Therefore, in the encryption device of the present invention, the data 120 corresponding to the least significant bit (D0 bit) position that hardly affects the gradation among the 8 bits is used as authentication data for authenticating the user.

FIG. 1D shows a case where data 120 corresponding to the least significant D0 bit position, that is, authentication data is designated. When the data is temporarily cut out to a storage device (not shown) as described above, it can be temporarily cut out from the storage device to another storage device (not shown).
In the data 120 corresponding to the D0 bit position, that is, in the authentication data, an authenticator indicating the identity is recorded in the portion of A150. Encrypted data is recorded in a portion of B160 other than the portion A150 where the authenticator is recorded in the authentication data, as described later. When the data is temporarily cut out in the storage device (not shown) as described above, it is written back to the original position in the digital image data 100. In any case, the authentication data can be embedded in the original digital image data 100 without substantially impairing the original gradation. In FIG. 1 (D), A150 is 80 bytes,
B160 is 20 bytes and the authentication data is exemplified as 100 bytes, but this is only for the purpose of explanation and is not limited to this number of bytes.

FIG. 2 is a flowchart showing one embodiment of the digital card creation in the encryption method of the present invention.

In FIG. 2, an area of 100 bytes, that is, an area of data 120 corresponding to the D0 bit position is defined as an area A150 of 80 bytes and an area B1 of 20 bytes.
60 (step S210).

An authenticator is recorded in an area A150, and an area B1 is recorded.
60 is cleared by data such as 0 bits. If the data is temporarily cut out to a storage device (not shown) as described above, A
Authentication data combining 150 and B160, that is, D
The area of the data 120 corresponding to the 0-bit position is written back to the original position in the digital image data 100 (step S220). At this point, you have a digital card that has not yet been encrypted.

The entire digital image data 110 including the authentication data and other image data is encrypted.
As a result of the encryption, encrypted data (hereinafter, referred to as “digest data”) equal to the length (20 bytes) of the area B160 is created (step S230). For this encryption, for example, a one-way function (one-way function) can be used. The one-way function is easy to encrypt, difficult to decrypt by a third party, and decrypts a legitimate recipient. It is desirable to use a trapdoor oneway function having a structure that is easy to perform, for example, RSA (Rivest Shamir Adlema).
n) Encryption or the like can be used.

The created digest data (length 2
0 byte) may be immediately recorded in the area B160,
This digest data can be further encrypted with, for example, the password of the receiver of the data destination to create encrypted digest data (length 20 bytes) (step S240). Thus, the length of the encrypted digest data is equal to the length of the original digest data (20 bytes). Various types of encryption such as public key encryption can be used for this encryption.

The encrypted digest data is stored in area B16.
0 is recorded (step S250). As a result, a digital card including an authenticator and encrypted digest data in part of the original image data is completed. As described above, the encrypted digest data is obtained by encrypting the entire digital image data including the image data and the authenticator with a one-way function, so that the digital card is falsified or decrypted. Is extremely difficult.

The completed digital card is sent to the receiver by the above-mentioned SSL protocol or the like. The digital card decrypted on the receiver side is easy to visually comprehend because the digital card includes image data 104 such as a photograph unlike a conventional digital certificate using only a document. As another embodiment of the image data 104, an image such as a seal stamp can be used. Further, a watermark pattern or the like can be used as the background of the entire image.

As an application of the digital card, various certificates such as an identification card, a license, a membership card, a copy of a family register, a copy of a registry, etc., as well as an invoice, a receipt, a payment form, a request form, and an order form. It can be used for a wide range of purposes, such as invoices, purchase applications, purchase (transaction) confirmations, contracts, postal orders, checks, bills, stock securities, and traveler's checks. Various cards such as credit card, charge card, revolving card, debit card, cash card, bank deposit (ATM)
Needless to say, it can be applied as a substitute for cards, postal savings cards, ID (identification) cards, various IC cards, and the like.

A recording medium on which a computer program for realizing the functions of the above-described embodiments is recorded is supplied to an encryption device having a computer, and the computer reads and executes the computer program stored on the recording medium. It goes without saying that the object of the present invention is also achieved by this. In this case, the computer program itself read from the recording medium implements the novel functions of the present invention, and the recording medium on which the computer program is recorded constitutes the present invention. Examples of the recording medium on which the computer program is recorded include a CD-ROM, a floppy disk,
A hard disk, ROM, memory card, optical disk, or the like can be used.

[0025]

As described above, according to the encrypting apparatus, the encrypting method and the recording medium of the present invention, an authenticator for authenticating a person is embedded in a digital image, and the entire digital image is encrypted. Accordingly, it is possible to provide an encryption device, an encryption method, and a recording medium that are difficult to forge and decipher by analogy or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an encryption method of the present invention.

FIG. 2 is a flowchart showing one embodiment of digital card creation in the encryption method of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 digital image data 102 issuing agency data 104 image data 106 expiration date data 108 other principal data 110 digital stripes 120, 121, 122, 123, 124, 125, 1
Data corresponding to bit positions 26 and 127 150 area A 160 area B

Claims (5)

[Claims] An encryption device for encrypting and embedding an authentication code in a part of digital image data, wherein the authentication data recording means records authentication data including the authentication code instead of a part of the digital image data. Encrypting means for encrypting the entire digital image data in which the authentication data is recorded by the authentication data recording means, and obtaining encrypted data of a length excluding the authenticator from the authentication data; And an encrypted data recording means for recording the encrypted data in a portion of the authentication data excluding the authenticator. 2. The encryption apparatus according to claim 1, wherein said authentication data recording means comprises: means for designating a part of said digital image data; and a predetermined bit position in said designated part of said digital image data. An encryption device comprising: means for designating data corresponding to the specified bit position; and means for recording the authentication data in place of the data corresponding to the designated predetermined bit position. 3. The encryption apparatus according to claim 1, wherein the encryption performed by the encryption means is encryption performed on the entire digital image data using a one-way function. Encryption device. 4. An encryption method for encrypting and embedding an authenticator in a part of digital image data, the method comprising: specifying a part of the digital image data; A step of specifying data corresponding to a predetermined bit position; a step of recording authentication data including the authenticator instead of the data corresponding to the specified predetermined bit position; Encrypting the entire image data using a one-way function to obtain encrypted data of a length excluding the authenticator from the authentication data; and encrypting the encrypted data with the authentication data. Recording an encrypted data in a portion excluding the authenticator therein. 5. A computer-readable recording medium on which a program for executing the encryption method according to claim 4 is recorded.