WO2011052180A1

WO2011052180A1 - Encrypted message transmission device, program, encrypted message transmission method and authentication system

Info

Publication number: WO2011052180A1
Application number: PCT/JP2010/006304
Authority: WO
Inventors: ハンケッセルス
Original assignee: Ｈａｎａｍａｒｕ株式会社
Priority date: 2009-10-27
Filing date: 2010-10-25
Publication date: 2011-05-05
Also published as: JP2011097192A

Abstract

In order to ensure the security of communication and easily detect the falsification of information, disclosed is an encrypted message transmission device provided with a message determination unit for determining a message to be transmitted to a user, a server image generation unit for generating a server image which makes the message viewable by the user by being combined with a token image possessed by the user or a token image generated by the user, and a transmission unit for transmitting the server image to the user. The encrypted message transmission device may be further provided with a challenge key generation unit for randomly generating a challenge key, the server image generation unit may generate the server image on the basis of a token pre-shared with the user and the challenge key, and the transmission unit may transmit the challenge key together with the server image.

Description

Encrypted message transmission device, program, encrypted message transmission method, and authentication system

The present invention relates to an encrypted message transmission device, a program, an encrypted message transmission method, and an authentication system.

An image encryption technique for encrypting an original image by dividing an image composed of black or white (transparent) pixels into two pieces of randomized pixel information is known (Non-Patent Document 1). In the image encryption technique, each pixel of the two divided images (shares) is randomized with black or white, and the original image cannot be viewed with only one share. However, you can see the original image by overlapping the two shares. In this specification, a pixel that does not transmit light is expressed as “black”, and a pixel that transmits light is expressed as “white”.

When communicating messages securely using image encryption technology, one share is kept secret for both sending and receiving, and the other share is sent using an insecure transmission path. On the receiving side, the message can be read by superimposing the confidential share and the received share. However, it is not preferable to use a share once used repeatedly. That is, it becomes possible to reveal the information of the securely held share from a plurality of intercepted shares, and it becomes difficult to ensure the safety of communication. Moreover, even if the intercepted share is falsified, the receiver cannot easily detect the falsification of the information.

In order to solve the above-described problem, in the first aspect of the present invention, a message determination unit that determines a message to be transmitted to the user is combined with a token image owned by the user or a token image generated by the user. Thus, an encrypted message transmission device is provided that includes a server image generation unit that generates a server image that makes a message visible to the user, and a transmission unit that transmits the server image to the user. The server image generation unit may generate a server image that makes the message visible to the user by performing an exclusive OR or OR operation on the token image with the bit unit.

The encrypted message transmitting apparatus further includes a receiving unit that receives user identification information, and a token storage unit that stores a token for generating a token image in association with the user identification information, and a server image generation unit May generate the server image based on the token image generated from the token stored in the token storage unit in association with the user identification information received by the reception unit. The message determination unit may determine the message as a combination of symbols in which the overlapped portions have the same shape when a plurality of symbols respectively included in the plurality of server images transmitted by the transmission unit are overlapped. The server image generation unit generates a server image as an image made up of a plurality of cells, places one of the symbols in each of some of the cells, and overloads in each cell in which one symbol is placed. You may arrange | position a symbol so that the wrapped part may become the same position. The color of all pixels in one cell, including the pixel occupied by the symbol and the pixels other than the pixel occupied by the symbol, is the same as the color of the corresponding pixel in any other cell; The one cell and the other cell may be at the same position in a plurality of different server images generated based on the same token image. The server image generation unit generates an image in each cell as an image composed of a plurality of pixels. The plurality of pixels are white or black. In each cell, each pixel other than the pixel occupied by the symbol is The color of each pixel may be determined by random number generation using a token, a cell position, and a symbol shared in advance as a seed. You may arrange | position the false symbol which does not comprise a message in any of the other cells except the one part cell where the symbol which comprises the message is arrange | positioned among several cells.

The token image and the server image have a plurality of pixels, and the server image generation unit is configured such that when the token image and the server image are combined, the pixels forming the message have different colors in the token image and the server image. A server image may be generated. The server image generation unit may generate a server image having a substantially equal number of black pixels and white pixels. When the token image and the server image are combined, the server image generation unit may generate the server image so that approximately 75% of pixels other than the part forming the message are black and approximately 25% are white. .

Alternatively, the apparatus further includes a challenge key generation unit that randomly generates a challenge key, and the server image generation unit generates a server image based on the token shared with the user in advance and the challenge key, and the transmission unit May send a challenge key along with the server image. The transmission unit may further transmit a server image and a message authentication code (MAC) of the challenge key. The encrypted message transmission device and the user terminal may generate a token image for each user request, and the server image generation unit may generate a different server image for each request from the user. A target image generation unit that generates a target image that is a color image or a black and white image based on the message is further included. The server image generation unit generates a server image from the target image and the token image. An image in which the message is visible to the user may be generated by performing an exclusive OR operation on the image and the server image in bit units.

Note that the encrypted message transmitting apparatus can be grasped as a program for causing the encrypted message transmitting apparatus to function, and can be grasped as an encrypted message transmitting method. Alternatively, a message determination unit that determines a message to be transmitted to the user and a token image owned by the user or a token image generated by the user are combined to generate a server image that makes the message visible to the user. An encrypted message transmission device including a server image generation unit and a transmission unit that transmits a server image to a user, and a reception device that receives the server image and decrypts the message by combining the server image and the token image It can be understood as an authentication system. In this case, based on each of two tokens or token images owned by the user (two tokens, two token images, or one token and one token image), Message sending device Therefore the first information and second information is decoded from each of the generated two servers images, and based on two information selected from the third information based on the password selected by the user, to authenticate the user. The above summary of the present invention does not enumerate all necessary features of the present invention. Also, a sub-combination of these feature groups can be an invention.

1 shows an example of a network system 100 to which the encrypted message transmission apparatus of the present embodiment is applicable. 1 shows a communication system 200 using the encrypted message transmitting apparatus of the present embodiment. An example of the communication method in the communication system 200 is shown. An example of a symbol is shown. An example of a symbol is shown. An example of a symbol is shown. An example when symbols are superimposed is shown. An example of an image when different server images Is are superimposed is shown. An example of an image when different server images Is are overlaid when the same symbol is arranged in a cell at the same position is shown. A state in which the server image Is and the static token image Its are combined is shown. A state in the middle of combining the server image Is and the static token image Its is shown. The overlap image Io in which the combination of the server image Is and the static token image Its is completed is shown. 9 shows a communication system 900 using an encrypted message transmission apparatus according to another embodiment. An example of the communication method in the communication system 900 is shown. An example of the communication method in the communication system 900 is shown. An example of the mode which displays message M is shown. An example of the mode which displays message M is shown.

Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

In the following embodiments, when expressed as “image”, image data that is processed by a computer system or the like and displayed on a liquid crystal display panel or the like as well as an image printed on paper or the like is also “image”. Include in concept. In this case, even if the image data represents one image as a group of digital data having a predetermined number of bits, all the image data is stored as long as the group of data can be sequentially processed and recognized as a series of image data. It need not be stored for storage. That is, some data may be generated for processing as image data, sequentially processed, and then discarded without being recorded.

FIG. 1 shows an example of a network system 100 to which the encrypted message transmitting apparatus of this embodiment can be applied. The network system 100 includes a remote authentication server 110, a service server 120, a client group 130, and a network 140, which are examples of encrypted message transmission devices. The client group 130 may include a personal computer 132, an information mobile terminal 134, and a mobile phone 136. Each device included in the remote authentication server 110, the service server 120, and the client group 130 has a communication function and can exchange messages with each other via the network 140.

The remote authentication server 110 generates a one-time password in response to a password request from the client group 130, generates an encrypted image incorporating the one-time password, and returns it to the requester of the client group 130. The request source reads the one-time password using the encrypted image and the key image, and inputs the read one-time password to the login screen of the service server 120 to request authentication. The service server 120 transmits a remote authentication request to the remote authentication server 110 together with the inputted one-time password, and delegates authentication of the request source to the remote authentication server 110. The remote authentication server 110 authenticates the transmitted one-time password and notifies the service server 120 whether the authentication has succeeded or failed. In another example, the service server 120 may redirect (redirect) the authentication request from the request source to the remote authentication server 110. In this case, the remote authentication server 110 redirects the request source to the service server 120 after the authentication of the input one-time password is completed.

The service server 120 transmits whether the authentication has succeeded or failed to the request source that issued the password request, and provides a service in response to the service request from the request source. The remote authentication server 110 and the service server 120 may be one system, and the service server 120 may authenticate instead of remote authentication. The service of the service server 120 is arbitrary, and may not provide the service as long as authentication is requested.

FIG. 2 shows a communication system 200 using the encrypted message transmitting apparatus of this embodiment. In the example of the communication system 200, a case where a secret key image used for encryption and decryption is static will be described.

The communication system 200 includes an encrypted message transmission device 210 provided as a partial function of the remote authentication server 110 and a reception device 250 provided as a partial function of the client group 130. The encrypted message transmission apparatus 210 includes a reception unit 212, a message determination unit 214, a target image generation unit 216, a token storage unit 218, a server image generation unit 220, a transmission unit 222, and a random number generation unit 224. The reception device 250 includes a transmission unit 252, a reception unit 254, a token image storage unit 256, an image overlay unit 258, and a message display unit 260.

The receiving unit 212 receives a challenge request from the receiving device 250. The challenge request may include identification information of a user who uses the receiving device 250, for example, a user ID. That is, the receiving unit 212 receives user identification information. Here, the challenge request can be exemplified by a request for transmitting a one-time password for authentication.

The message determination unit 214 determines a message M to be transmitted to the user in response to a challenge request from the user. The message M is information intended to be securely transmitted to the receiving device 250, and can be exemplified by a one-time password used for user authentication, for example. The target image generation unit 216 generates a target image It based on the determined message M.

The token storage unit 218 stores the static token image Its in association with a user ID that is an example of user identification information. The token storage unit 218 may store an image shared with the user as a static token image Its. In another example, instead of the static token image Its, a token previously shared with the user, for example, a random number sequence is stored, and the token is used as a seed for random number generation. May be generated.

The server image generation unit 220 generates a server image Is that makes the message M visible to the user by being superimposed and combined with the static token image Its owned by the user. The server image generation unit 220 generates a server image Is based on the static token image Its stored in the token storage unit 218 in association with the user ID received by the reception unit 212. The transmission unit 222 transmits the server image Is to the user.

The transmission unit 252 transmits a challenge request together with the user ID. The receiving unit 254 receives the server image Is. The token image storage unit 256 stores the user's static token image Its. The static token image Its stored in the token image storage unit 256 is the same as the static token image Its stored in the token storage unit 218 of the encrypted message transmission apparatus 210.

The image superimposing unit 258 superimposes the server image Is received by the receiving unit 254 and the static token image Its stored in the token image storage unit 256. The message display unit 260 displays an overlap image Io in which the server image Is and the static token image Its are superimposed.

FIG. 3 shows an example of a communication method in the communication system 200. In the following description, the process performed by the encrypted message transmission apparatus 210 will be described as a server process, and the process performed by the reception apparatus 250 will be described as a client process.

The client and server share the static token image Its as a secret token for each user. Instead of the static token image Its, a seed for generating the static token image Its may be held.

The server may generate the message M using a symbol. The symbol is selected from a symbol set consisting of a plurality of symbols. The symbol set is configured such that if any two symbols are selected, the overlapping pixel regions of the selected symbol pair are always the same. For example, if the symbol set is “o”, “8”, “g”, “p”, “q”, “b” and “d”, the overlapping symbols are “o” and are always equal . 4, 5 and 6 show “p”, “q” and “8” which are examples of symbols where the overlapping pixel regions are always the same. Each symbol has a pixel region corresponding to “o”, and when this region is overlapped, the result is as shown in FIG. That is, all symbols have “o” which is a common overlap region. By using such a symbol set, it is possible to prevent an attacker who tries to break the encryption from estimating a part of the secret static token image Its.

The target image It, the static token image Its and the server image Is have the same size and are divided into i × j cells. Each cell is composed of n × m pixels. Each pixel may be either black or white.

First, the client transmits a challenge request to the server (step 302). The request includes a user ID. The server receives the request (step 304) and determines the message M (step 306).

The server further generates a target image It from the message M (step 308). The target image It is generated by arranging each symbol constituting the message M in each cell of i × j. Cells in which no symbol is placed may be left blank.

The server acquires the static token image Its (step 310). The static token image Its is read if it is recorded in the token storage unit 218, and if a seed necessary for generating the static token image Its is recorded, a pseudo random number is generated from the seed. Thus, the static token image Its can be generated.

The server generates a server image Is from the target image It and the static token image Its (step 312). The server generates a server image Is for each cell. When the target cell of the target image It does not include a symbol, black or white is randomly set for each pixel in the cell of the server image Is. When the target cell of the target image It includes a symbol, the server image Is in each cell is generated by the following procedure for each pixel. When the pixel of interest in the target image It is white, the pixel is randomly set to either black or white using a pseudo-random number generated by the random number generator 224. When the pixel of interest in the target image It is black, if the corresponding pixel of the static token image Its is white, the corresponding pixel of the server image Is is set to black. If the corresponding pixel of the static token image Its is black, the server image Is Set the pixel to white.

That is, the static token image Its and the server image Is have a plurality of pixels, and the plurality of pixels are white or black. In the server image generation unit 220, the server image Is is converted into the static token image Its and the server image Is. The server image Is is generated so that the pixels of the part that forms the message M when they are overlaid have different colors in the static token image Its and the server image Is.

Note that the symbols are arranged so that the overlapping portions of the symbols are always in the same position in each cell. As a result, even if a plurality of server images Is are overlapped, only the common portion where the symbols overlap as shown in FIG. 8, and no other knowledge is given to the attacker. In addition, the random number generation unit 224 can be set with a seed that combines the symbol identifier, the position of the cell in the image, and the bits of the static token image Its. Thereby, when different server images Is in which the same symbol is arranged at the same position of the corresponding cell are overlaid, either the pixel that becomes a part of the symbol or the pixel that becomes a part of the background , The pixel pattern generated in that cell will be exactly the same. As a result, an image obtained by superimposing a plurality of server images Is only shows 50% transmittance in the portion as shown in FIG. 9, and does not give useful knowledge to the attacker.

It should be noted that a fake message fake symbol may be incorporated into a cell of the server image Is where the message M symbol is not arranged. A fake symbol of a fake message can be generated by randomly selecting a symbol again from the symbol set. The fake symbols that make up the fake message can be placed in empty cells of the target image It. In this case, the random number generation for the cell in which the false symbol is arranged is performed by using the random number generator 224 to store the random key for the false message stored in association with the symbol identifier, the cell position in the image, and the static token image Its. This can be achieved by setting a combined seed. Such a fake message can provide stronger encryption strength. Further, in the above encryption method, even if the server image Is is tampered during communication, in many cases, a continuous black area is generated in the symbol formation area, so that the fact of tampering can be easily visually confirmed. Can be detected.

The server transmits the server image Is to the client (step 314). The client superimposes the received server image Is and the held static token image Its (step 316).

10 to 12 show a state in which the server image Is and the static token image Its are superimposed. FIG. 10 is a server image Is and a static token image Its before being superimposed, each having an aperture ratio of approximately 50% (ratio of the number of white pixels to the total number of pixels), and each pixel of white or black is random Is arranged. Therefore, information cannot be read only from the server image Is.

FIG. 11 shows a state in the middle of superimposing the server image Is and the static token image Its. Pixels in the overlapped region are white when both the server image Is and the static token image Its are white, and are black when either is black. Therefore, the aperture ratio of the overlapped region is approximately 25%.

FIG. 12 shows the overlap image Io that has been superposed. Since 100% of the pixels in the message M portion of the target image It are black, the character “qpg88g” that is the message M can be easily visually recognized. That is, when the static token image Its and the server image Is are superimposed, the server image Is is generated so that approximately 75% of the pixels other than the part forming the message M are black and approximately 25% are white. .

The client displays the overlap image Io generated by the superposition (step 318) and causes the user to read the message M (step 320). The user can receive the service from the service server or the like by inputting the read message M as a password, for example (step 322).

FIG. 13 shows a communication system 900 using an encrypted message transmission apparatus according to another embodiment. In the example of the communication system 900, a case where a secret key image used for encryption and decryption changes dynamically will be described. The communication system 900 includes an encrypted message transmission device 910 provided as a partial function of the remote authentication server 110 and a reception device 950 provided as a partial function of the client group 130.

The encrypted message transmission device 910 includes a reception unit 912, a server challenge key generation unit 914, a token storage unit 916, a seed generation unit 918, a random number generation unit 920, a message determination / target image generation unit 922, a server image generation unit 924, a MAC A calculation unit 926 and a transmission unit 928 are included. The receiving device 950 includes a client challenge key generation unit 952, a transmission unit 954, a reception unit 956, a MAC calculation unit 958, a MAC verification unit 960, a token storage unit 962, a seed generation unit 964, a random number generation unit 966, an image combination unit 968, and A message display unit 970 is provided. A dynamic token may be read out by providing a storage unit that stores the dynamic token.

The receiving unit 912 receives a challenge request from the receiving device 950. The challenge request includes the client challenge key CKc generated by the client challenge key generation unit 952 of the receiving device 950. The challenge request can include user identification information such as a user ID.

The server challenge key generation unit 914 randomly generates server challenge keys CKs. The server challenge key CKs is an encryption parameter used together with the client challenge key CKc during a series of operations for processing a challenge request from the user. The server challenge key CKs and the client challenge key CKc are randomly determined for each series of processes. The server challenge key CKs may be dynamically changed every predetermined lifetime, for example, every minute.

The token storage unit 916 stores the dynamic token Td. The dynamic token Td is shared between the encrypted message transmission device 910 that is a server and the reception device 950 that is a client.

The seed generation unit 918 generates a seed S for generating pseudorandom numbers using the server challenge key CKs, the client challenge key CKc, and the dynamic token Td.

The random number generation unit 920 generates a pseudo random number using the seed S generated by the seed generation unit 918 as an initial value. The bit stream output from the random number generator 920 has a length obtained by multiplying the number of pixels of the width of the target image, the number of pixels of the height, and the number of color depths that each pixel can indicate, and If converted into pixels of a predetermined color depth, it becomes visible as one image and is used as a dynamic token image Itd.

The message determination / target image generation unit 922 determines the message M and generates a target image It based on the message M. The message M does not need to be selected from the symbol set as in the communication system 200. Arbitrary characters, images, etc. can be selected as the message M. Further, if the number of color depths of the target image It and the dynamic token image Itd is the same, the target image It (message M) does not necessarily need to be composed of white and black. The target image It is not limited at all, and can be a color image composed of a large number of colors.

The server image generation unit 924 generates a server image Is from the target image It and the dynamic token image Itd that is a bit stream generated by the random number generation unit 920. Specifically, the server image generation unit 924 generates the server image Is by performing an exclusive OR (XOR) on the target image It and the dynamic token image Itd in bit units. Since the bitstream is formed based on the seed S generated from the dynamic token Td, the server challenge key CKs, and the client challenge key CKc, the server image generation unit 924 has a token (dynamic A server image Is is generated based on the token Td) and the challenge key (server challenge key CKs or client challenge key CKc).

The MAC calculation unit 926 calculates a message authentication code (MAC) of the server image Is and the server challenge key CKs to be communicated. For example, it can be calculated by applying a keyed hash function using the dynamic token Td as a key to a message obtained by adding the client challenge key CKc to the server image Is and the server challenge key CKs. The transmission unit 928 transmits the server challenge key CKs together with the server image Is. Moreover, you may transmit MAC. The MAC may also be calculated for the client challenge key CKc. The MAC is not limited to a keyed hash function.

The client challenge key generation unit 952 randomly generates a client challenge key CKc. The client challenge key CKc is used together with the server challenge key CKs during a series of operations for processing a challenge request from the user.

The transmission unit 954 transmits a challenge request together with the user ID and the client challenge key CKc. The receiving unit 956 receives the server image Is, the server challenge key CKs, and the MAC.

The MAC calculation unit 958 calculates a message including the received server image Is and server challenge key CKs and a held client challenge key CKc by applying a keyed hash function using the dynamic token Td as a key. The MAC verification unit 960 compares the MAC calculated by the MAC calculation unit 958 and the MAC received by the reception unit 956, and interrupts the processing if they are different. As a result, it is possible to detect message tampering during communication.

The token storage unit 962 stores the dynamic token Td. The seed generation unit 964 generates a seed S. The random number generation unit 966 generates a pseudo random number bit stream having the seed S as an initial value as a dynamic token image Itd. The token storage unit 962, the seed generation unit 964, and the random number generation unit 966 are the same as the token storage unit 916, the seed generation unit 918, and the random number generation unit 920.

The image combination unit 968 generates a combination image Ic from the server image Is received by the reception unit 956 and the dynamic token image Itd generated by the random number generation unit 966. Specifically, the image combination unit 968 generates a combined image Ic by performing exclusive OR (XOR) on the server image Is and the dynamic token image Itd in units of bits. The message display unit 970 displays the combination image Ic. In this case, the combination image Ic is the same as the target image It. Note that the image combination unit 968 may generate the combination image Ic by superimposing the server image Is and the dynamic token image Itd by performing a logical OR (OR) on a bit basis. In this case, the combined image Ic is composed of only white or black pixels, 100% of the pixels forming the message M are black, and approximately 50% of the pixels other than the parts forming the message M are black. Become.

14 and 15 show an example of a communication method in the communication system 900. FIG. In the following description, the processing by the encrypted message transmission device 910 will be described as server processing, and the processing by the reception device 950 will be described as client processing. The client and server share a dynamic token Td that is a random character string for each user. The dynamic token Td is kept secret. The client and server use a pseudo-random number generation (PRNG) algorithm and a message authentication code (MAC) independently. Client and server must agree to use the same PRNG algorithm and the same MAC algorithm (eg, HMAC-SHA256), and PRNG must be cryptographically secure and deterministic .

The client generates a client challenge key CKc that is a random character string (step 1002). The client requests a challenge with the user ID and client challenge key CKc from the server (step 1004).

When the server receives the request (step 1006), it generates a server challenge key CKs (step 1008). The server further calls the dynamic token Td (step 1010) and generates a seed S from the client challenge key CKc, the server challenge key CKs and the dynamic token Td (step 1012). The seed S is set to the initial value of the random number generator 920 (step 1014). The server operates the random number generation unit 920 to generate a bit stream of pseudo random numbers, and generates a dynamic token image Itd (step 1016).

The server determines the message M (step 1018) and generates the target image It (step 1020). The server further generates a server image Is by performing an exclusive OR (XOR) on the target image It and the dynamic token image Itd in units of bits (step 1022).

The server calculates the MAC by, for example, HMAC-SHA256 from the server image Is, the server challenge key CKs, and the client challenge key CKc using the dynamic token Td as a key (step 1024). The server transmits the server image Is, the server challenge key CKs, and the MAC to the client (step 1026).

The client receives the server image Is, the server challenge key CKs, and the MAC from the server (step 1028), and uses the dynamic token Td as a key, and holds the client challenge key CKc held as the received server image Is and the server challenge key CKs. The MAC is calculated from the above and is compared with the received MAC (step 1030). If the collation does not match, the process is interrupted. If the collation matches, the process proceeds to step 1032 and the process is continued.

The client generates a seed S from the client challenge key CKc, the server challenge key CKs, and the dynamic token Td, sets the seed S to an initial value of the random number generation unit 966 (step 1032), and generates a pseudo-random bit stream. Then, the dynamic token image Itd is generated (step 1034).

The client performs exclusive OR (XOR) on the received server image Is and dynamic token image Itd in bit units (step 1036), displays the generated combined image Ic (step 1038), and sends a message M to the user. Read (step 1040). The user can receive the service from the service server or the like by inputting the read message M as a password, for example (step 1042). The personal identification number PIN can be added to the read message M as the password.

According to the example of the communication system 900, both the dynamic token image Itd and the server image Is are dynamically changed for each challenge request. By using a cryptographically secure random number generator, it can be ensured that the dynamic token image Itd and the server image Is cannot be predicted based on the leaked or intercepted past server image Is. Further, since the server and the client generate the random server challenge key CKs and the client challenge key CKc, respectively, and use them for encryption, it is possible to prevent a replay attack in which communication data is intercepted and reproduced. In addition, since the MAC is sent together with the server image Is, the communication data cannot be falsified.

The static token image Its described in the communication system 200 can be combined with the dynamic token image Itd used in the communication system 900. In such a case, it is possible to add a password selected by the user, for example, a personal identification number PIN, and perform personal identification with three elements. For example, authentication is normally performed with two of the three elements. It can be operated as follows. In normal operation, if authentication is performed using the dynamic token images Itd and PIN, or the static token images Its and PIN, it becomes impossible to log in if the PIN is lost. However, if authentication can be performed by combining the three elements, it is possible to authenticate with the dynamic token image Itd and the static token image Its, permit login, and issue a new PIN to the login user. Also, two of the three elements may be used to regenerate the dynamic token Td. For example, in the case of a new PC or mobile device, or when the PC or mobile device is lost or stolen, the dynamic token Td needs to be regenerated. So what is your favorite pet name? Or what is your mother's maiden name? Compared to a system that authenticates a user by a predetermined personal question such as the above and reissues the dynamic token Td, or a system that makes a phone call to the help desk and reissues the dynamic token Td. A highly functional system can be provided.

16 and 17 show an example of a mode for displaying the message M. FIG. The example of FIG. 16 is a display example of a browser, for example, and a message M is displayed on the browser together with a password input field. The user can request authentication by reading the message M and typing the read message M in the password input field. In addition to the message M, a simple personal identification number PIN may be requested for the password required for authentication. If the communication system 900 of this embodiment is used, a secure one-time password can be provided as the message M, and the user does not need to memorize a complicated password.

FIG. 17 shows an example of displaying the message M on the portable information terminal. For example, when service login is performed via a personal computer, a one-time password for login authentication can be provided through a communication path of the portable information terminal different from the communication path used for login and service. Thereby, security can be further enhanced.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

The execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior”. It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for the sake of convenience, it means that it is essential to carry out in this order. is not.

DESCRIPTION OF SYMBOLS 100 Network system 110 Remote authentication server 120 Service server 130 Client group 132 Personal computer 134 Information portable terminal 136 Cellular phone 140 Network 200 Communication system 210 Encrypted message transmission apparatus 212 Receiving part 214 Message determination part 216 Target image generation part 218 Token storage part 220 server image generation unit 222 transmission unit 224 random number generation unit 250 reception device 252 transmission unit 254 reception unit 256 token image storage unit 258 image superposition unit 260 message display unit 900 communication system 910 encrypted message transmission device 912 reception unit 914 server challenge Key generation unit 916 Token storage unit 918 Seed generation unit 920 Random number generation unit 922 Message determination / target image generation unit 924 server image generation unit 926 MAC calculation unit 928 transmission unit 950 reception apparatus 952 client challenge key generation unit 954 transmission unit 956 reception unit 958 MAC calculation unit 960 MAC collation unit 962 token storage unit 964 seed generation unit 966 Random number generator 968 Image combination unit 970 Message display unit CKc Client challenge key CKs Server challenge key Ic Combined image Io Overlap image Is Server image It Target image Itd Dynamic token image Its Static token image M Message PIN Personal identification number S Seed Td Dynamic token

Claims

A message determination unit for determining a message to be transmitted to the user;
A server image generation unit that generates a server image that is visible to the user by being combined with a token image owned by the user or a token image generated by the user;
An encrypted message transmission device comprising: a transmission unit that transmits the server image to the user.
2. The encrypted message according to claim 1, wherein the server image generation unit generates the server image that makes the message visible to the user by performing an exclusive OR or an OR operation on the token image in bit units. Transmitter device.
A receiving unit for receiving user identification information;
A token storage unit that stores a token for generating the token image in association with the user identification information;
The server image generation unit generates the server image based on the token image generated from the token stored in the token storage unit in association with the user identification information received by the reception unit. Item 3. The encrypted message transmitting device according to Item 1 or 2.
The message determination unit determines the message as a combination of symbols in which the overlapped portions have the same shape when a plurality of symbols respectively included in the plurality of server images transmitted by the transmission unit are overlapped. The encrypted message transmission apparatus according to claim 3.
The server image generation unit generates the server image as an image composed of a plurality of cells,
Placing one of the symbols in each of some of the plurality of cells;
The encrypted message transmitting apparatus according to claim 4, wherein the symbols are arranged so that the overlapped portions are located at the same position in each cell in which one symbol is arranged.
The color of all pixels of one cell including the pixel occupied by the symbol and the pixels other than the pixel occupied by the symbol are the same as the color of the corresponding pixel of any other cell;
The other cell includes the same symbol as the one cell,
6. The encrypted message transmission device according to claim 5, wherein the one cell and the other cell are in the same position in a plurality of different server images generated based on the same token image.
The server image generation unit generates an image in each cell as an image composed of a plurality of pixels,
The plurality of pixels are white or black;
In each cell, for each pixel other than the pixel occupied by the symbol, the color of each pixel is determined by generating a random number using the token, the position of the cell, and the symbol as a seed. The encrypted message transmitting apparatus according to claim 6, wherein the encrypted message transmitting apparatus is determined.
The false symbol that does not constitute the message is arranged in any one of the plurality of cells other than the partial cell in which the symbol that constitutes the message is arranged. The encrypted message transmitting device described in 1.
The token image and the server image have a plurality of pixels,
The server image generation unit generates the server image in which pixels of a part forming the message have different colors between the token image and the server image when the token image and the server image are combined. The encrypted message transmission device according to any one of claims 1 to 8.
The encrypted message transmission device according to claim 9, wherein the server image generation unit generates the server image having a substantially equal number of black pixels and white pixels.
When the token image and the server image are combined, the server image generator generates the server image so that approximately 75% of pixels other than the part forming the message are black and approximately 25% are white. The encrypted message transmitting apparatus according to claim 10, which generates a message.
It further includes a challenge key generation unit that randomly generates a challenge key,
The server image generation unit generates the server image based on a token shared in advance with the user and the challenge key,
The encrypted message transmission device according to claim 3, wherein the transmission unit transmits the challenge key together with the server image.
The encrypted message transmission device according to claim 12, wherein the transmission unit further transmits a message authentication code (MAC) of the server image and the challenge key.
The encrypted message transmission device and the user terminal generate the token image for each user request,
The encrypted message transmission device according to claim 13, wherein the server image generation unit generates a different server image for each request from the user.
A target image generating unit that generates a target image that is a color image or a black and white image based on the message;
The server image generation unit generates the server image from the target image and the token image,
The encrypted message transmission device according to claim 14, wherein the user terminal generates an image in which the message is visible to the user by performing an exclusive OR of the token image and the server image in bit units. .
A program for causing a computer to function as the encrypted message transmission device according to any one of claims 1 to 15.
A message determination stage for determining a message to be communicated to the user;
A server image generation step of generating a server image that is visible to the user by being combined with a token image owned by the user or a token image generated by the user;
An encrypted message transmission method comprising: a transmission step of transmitting the server image to the user.
In relation to each of two tokens or token images owned by a user, from each of the two server images generated by the encrypted message sending device according to any one of claims 1 to 15. An authentication system for authenticating the user based on two pieces of information selected from the decrypted first information and second information and third information based on a password selected by the user.