JP2014098773A - Encryption system, decryption server, encryption method, and decryption program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of decrypting data encrypted in a terminal by a server without exchanging an encryption key between the server and the terminal.SOLUTION: A decryption server 20 includes a database for storing a value generated by applying a different input value to a unidirectional function formed by applying a plurality of initial values to a polynomial with symmetry between the input value and a generated value, the input value, the initial values, and the polynomial in association with each other. A digital broadcasting receiver 10 generates a generation value by providing a different input value to a unidirectional function formed by applying an optional initial value to the polynomial, generates an encrypted data by providing data divided correspondingly to the number of digits of the input value to the unidirectional function and transmits the generated encryption data to the decryption server 20. The decryption server 20 retrieves a polynomial and an initial value respectively overlapped out of polynomials and initial values related to the received plurality of generation values and input values and reads out the retrieved polynomial and initial value and the generation value from the database and decrypts the encrypted data.

Description

  The present application relates to an encryption system, a decryption server, an encryption method, and a decryption program.

  In recent years, with the development of communication networks such as the Internet, opportunities for exchanging personal information via communication lines have increased. Under such circumstances, leakage of personal information and data alteration due to data interception on a communication line are problematic. In order to solve this problem, various cryptographic processing algorithms have been proposed. Among them, a representative technique is a technique for encrypting personal information transmitted and received between a server and a terminal using a hash function (for example, Patent Document 1).

  Patent Document 1 shares the hash function and the initial value between the terminal and the server, and maintains the confidentiality of the position of the terminal serving as personal information by using the generated value calculated using these. . Furthermore, when the terminal has moved, the server to which the terminal has moved receives the hash count from the server that shares the hash function and the initial value, and the server to which the terminal and the terminal have moved has the hash count, By calculating the hash, the same generated value is calculated and used by the terminal and the server, and the confidentiality of the terminal is maintained.

JP 2009-094940

  In the technique described in Document 1, a fixed authentication key (encryption key) is set between the server and the terminal and exchanged between the server and the terminal in advance. Therefore, if the authentication key itself leaks, the meaning of encryption itself will not be achieved.

  Therefore, the present invention is to provide a technique capable of decrypting encrypted data without exchanging an encryption key between a server and a terminal.

  The present invention for solving the above-mentioned problem is an encryption system, and is different for each one-way function obtained by applying a plurality of initial values to each of polynomials having symmetry between an input value and a generated value. A database in which a generated value generated by giving an input value and an input value used to generate the generated value, an initial value, and a polynomial are stored in association with each other, and an arbitrary polynomial in the polynomial has an arbitrary A different input value is given to the one-way function to which the initial value is applied to generate a generated value from each input value, and the one-way function used to generate the generated value is set to the number of digits of the input value. A plurality of generated values transmitted in the database based on a generating means for generating encrypted data by giving the data divided together as input values, and a plurality of generated values and input values transmitted When A search means for searching for a polynomial and an initial value in which the polynomial associated with the force value and the initial value overlap each other, and the polynomial and initial value searched by the search means, and generated by the generation means And decrypting means for decrypting the encrypted data by reading out a generated value associated with the encrypted data from the database.

  The present invention for solving the above problem is a decryption server for decrypting encrypted data, wherein a plurality of initial values are applied to each of a symmetric polynomial between an input value and a generated value. A generated value generated by giving different input values to each one-way function and the input value, initial value, and polynomial used to generate the generated value are stored in association with each other and transmitted. The generation value generated from each input value by giving different input values to the one-way function obtained by applying an arbitrary initial value to an arbitrary polynomial in the polynomial, and the generation value generated Based on the input value, a search is made for a polynomial and an initial value in which the generated value and the input value associated with the plurality of generated values and input values that are transmitted in the database overlap each other. And the encrypted data generated by giving, as an input value, data divided according to the number of digits of the input value to the one-way function used for generating the generated generated value, And a decryption means for decrypting the encrypted data by reading out a generated value associated with the polynomial and the initial value retrieved by the retrieval means from the database.

  The present invention for solving the above-described problem is an encryption method, which is a one-way function obtained by applying an arbitrary initial value to an arbitrary polynomial in a polynomial symmetric between an input value and a generated value. A generated value generation step for generating a generated value from each input value by giving different input values to the input, a dividing step for dividing the data according to the number of digits of the input value, and a generated value generated by the generated value generating step Based on the encrypted data generation step of generating the encrypted data by giving the data divided in the division step as an input value to the one-way function used in the above, and the plurality of sets of generated values and input values transmitted Generated values obtained by giving different input values to each one-way function obtained by applying a plurality of initial values to each of the polynomials having symmetry between the input value and the generated value, and the generated value Used to generate In the database in which the input value, the initial value, and the polynomial are stored in association with each other, the polynomial and the initial value that are associated with the plurality of generated values and the input value that are transmitted overlap each other. A retrieval step for retrieving a polynomial and an initial value, and a generated value associated with the polynomial and initial value retrieved in the retrieval step and the encrypted data generated in the generated value generation step are read from the database. And a decrypting step for decrypting the encrypted data.

  The present invention for solving the above problem is a decryption server program for decrypting encrypted data, wherein the program uses the decryption server as a polynomial having symmetry between an input value and a generated value. Receives a generated value generated from each input value by giving different input values to a one-way function that applies an arbitrary initial value to an arbitrary polynomial in it, and the input value given when generating this generated value Then, based on the received generated value and the input value, a different input is applied to each one-way function obtained by applying a plurality of initial values to each of the polynomials having symmetry between the input value and the generated value. A plurality of generated values and input values transmitted in a database in which a generated value generated by giving a value and an input value, an initial value, and a polynomial used to generate the generated value are stored in association with each other; Retrieval means for retrieving a polynomial and an initial value, each of which is associated with an associated polynomial and an initial value, and a one-way function used to generate the generated generated value, Encrypted data by reading from the database the encrypted data generated by giving the data divided according to the number of digits as an input value, and the generated value associated with the polynomial and initial value searched by the search means It is made to function as a decoding means which decodes.

  According to the present invention, the encrypted data can be decrypted without exchanging the encryption key between the server and the terminal.

It is a schematic diagram of a 1st embodiment. It is a block diagram of the digital broadcast receiver in 1st Embodiment. It is a block diagram of the decoding server in 1st Embodiment. It is an example of a database. It is a flowchart for demonstrating the operation | movement in 1st Embodiment. It is a flowchart for demonstrating the operation | movement in 2nd Embodiment. It is a schematic diagram of 3rd Embodiment. It is a block diagram of the digital broadcast receiver in 3rd Embodiment. An example of a material image pattern of 1 cell × 9 cells is shown. It is the figure which showed the example of a 4 type two-dimensional code image (33 cells x 33 cells). It is a schematic diagram of 4th Embodiment. It is a block diagram of the terminal in 4th Embodiment.

  In the present invention, an input value (INPUT) is given to an irreversible one-way function H uniquely defined by a polynomial (P) and an initial value (I) to calculate a generated value (OUTPUT). System. In the present invention, collision is avoided by using a polynomial and an initial value that are symmetrical between the input value and the generated value. In the following description, a hash function is used as the one-way function. However, a hash function other than the hash function may be used as long as it is a one-way function that can avoid collision.

<First Embodiment>
In order to explain the features of the present invention, it will be specifically described below with reference to the drawings.

(Constitution)
As shown in FIG. 1, the communication system according to the present invention includes a digital broadcast receiver 10, a decryption server 20 that decrypts data encrypted by the digital broadcast receiver 10, and a broadcast station 30. The machine 10 and the decryption server 20 are connected via the Internet.

(Digital broadcast receiver)
As shown in FIG. 2, the digital broadcast receiver 10 includes a broadcast side transmission / reception unit 101, a memory 102, a generation unit 103, a random number generation unit 104, a network side transmission / reception unit 105, and a data unit 106.

  The broadcast-side transmitting / receiving unit 101 receives a command description transmitted from the broadcast station 30 via a broadcast wave through data broadcasting, and executes it on its own device. In the instruction description, an instruction sentence of a hash function is described. In addition, the instruction description declares the radix and the number of digits of the input value, and the radix and the number of digits of the input value used in the digital broadcast receiver are predetermined. Further, the broadcast-side transmitting / receiving unit 101 receives a plurality of polynomials that can be used for the hash function via the broadcast wave and stores them in the memory 102.

  The generation unit 103 randomly selects one from a plurality of polynomials stored in the memory 102. An initial value is randomly generated from the random number generation unit 104 and one is selected. Next, the generation unit 103 randomly generates two different input values from the random number generation unit 104, and gives them to a hash function made up of a polynomial and an initial value to generate generated values.

  Finally, the generation unit 103 divides the data in the data unit 106 in accordance with the number of digits of the input value, and gives the data divided into hash functions composed of the selected polynomial and initial value as the input value to generate An encrypted data group that is an aggregate of encrypted data that is a value is created. When the number of digits of data in the data portion 106 is the same as the number of digits of the input value, it is not necessary to divide the data.

  The network side transmitting / receiving unit 105 transmits two sets of input values and generated values, and an encrypted data group to the decryption server 20. In this embodiment, the case where two sets of input values are given will be described. However, it is not necessary to limit the number of sets, and two sets or more may be used.

(Decryption server)
The decoding server 20 is a server prepared on the broadcasting station side. The decryption server 20 includes a transmission / reception unit 201, a database 202, a search unit 203, and a decryption unit 204.

  The transmission / reception unit 201 receives two sets of input values and generated values and an encrypted data group from the digital broadcast receiver 10.

  As shown in FIG. 4, the database 202 is generated by giving different input values to each one-way function obtained by applying a plurality of initial values to each of the polynomials having symmetry between the input values and the generated values. The generated value and the input value, initial value, and polynomial used to generate the generated value are stored in association with each other. The input value is a value in which a base number and a digit number used in advance with the digital broadcast receiver are determined. The generated value is a value calculated in advance by a hash function using an input value, an initial value, and a polynomial associated with each other.

  Based on the received two sets of input values and generated values, the search unit 203 is a polynomial in which the polynomials associated with the received two sets of input values and generated values and the initial values overlap in the database. And initial values are searched. In addition, the search unit 203 confirms whether the polynomial selected by the digital broadcast receiver 10 is one of the polynomials changed at a predetermined time.

  The decrypting unit 204 decrypts the received encrypted data into data that is an input value using the polynomial and the initial value searched by the searching unit 203. The decryption of the encrypted data is performed by reading from the database 202 the input value associated with the encrypted data, the searched polynomial and the initial value.

  In addition, although the said database may prepare the huge database which linked | related the input value, the initial value, and the production | generation value beforehand for every polynomial, it is not realistic. Therefore, the polynomial that can be selected by the generation unit 103 of the digital broadcast receiver is determined in advance, the polynomial that can be selected is changed every predetermined time, and the database range that the search unit 203 searches is limited accordingly. desirable. At this time, a polynomial that can be selected by the generation unit 103 of the digital broadcast receiver is transmitted from the broadcast station 30 described later to the digital broadcast receiver 10 via a broadcast wave as a data broadcast. And a configuration in which the search unit 203 confirms whether the searched polynomial corresponds to one of the polynomials that can be selected at a predetermined time. Become.

(Broadcaster)
As described above, the broadcast station 30 transmits to the digital broadcast receiver 10 the command description in which the hash function command statement, the decimal number of the input value, and the number of digits are declared by data broadcasting via the broadcast wave. Further, a plurality of polynomials that can be used for the hash function are transmitted by data broadcasting via a broadcast wave. The broadcast station 30 changes a usable polynomial with the digital broadcast receiver 10 every predetermined time. This predetermined time is preferably set according to the number of digits between the input value and the initial value. This is because the polynomial used and the initial value may be found when calculating by brute force.

(Operation)
Next, the operation of the present embodiment will be described. In the following description, it is assumed that a plurality of polynomials that can be used from the broadcast station 30 to the digital broadcast receiver 10 have already been transmitted and stored in the memory 102. Further, it is assumed that an initial value to be similarly used is generated by the random number generation unit 104 and stored in the memory 102. In the following description, the case where the input value is 2 hexadecimal digits, the initial value is 4 hexadecimal digits, and the polynomial is 4 hexadecimal digits is explained. However, the decimal number and the number of digits need not be limited to these. Shall.

  The generation unit 103 selects one polynomial and an initial value used in the hash function from the memory 102 (step 501). Here, it is assumed that the polynomial “0x1001” and the initial value “0x95FA” are selected.

  The generation unit 103 randomly extracts two different input values generated by the random number generation unit 104 (step 502). Here, it is assumed that “0x96” and “0xFC” are extracted.

  The input values “0x96” and “0xFC” are given to the hash function composed of the selected polynomial “0x1001” and the initial value “0x95FA” to generate respective generated values (step 503). It is assumed that the generated value generated here is the generated value “0x6096” for the input value “0x96” and the generated value “0xCD13” for the input value “0xFC”.

  Further, the generation unit 103 divides the data in the data unit 106 into two hexadecimal digits and gives each to a hash function composed of the selected polynomial and initial value, and is a set of four hexadecimal hexadecimal generation values. Is created (step 504). Here, it is assumed that the encrypted data group is “0x7197, 0xDC12,...”. Note that “,” in this description indicates a delimiter of the data group, and is not a part of the encrypted data or the decrypted data.

  The network-side transmitting / receiving unit 105 of the digital broadcast receiver 10 transmits two sets of input values, generated values, and an encrypted data group to the decryption server 20 (step 505). Here, the two sets of input values and generated values are “0x96, 0x6096” and “0xFC, 0xCD13”, and the encrypted data group is “0x7197, 0xDC12,...”.

  The transmission / reception unit 201 of the decryption server 20 receives the two sets of input values and generated values and the encrypted data group from the digital broadcast receiver 10 (step 506). Two sets of input values and generated values received here are “0x96, 0x6096” and “0xFC, 0xCD13”, and the encrypted data group is “0x7197, 0xDC12,...”.

  The search unit 203 uses the received two sets of input values and generated values, and in the database, the polynomials associated with the received two sets of input values and generated values and the initial values overlap each other. And the initial value are searched (step 507). Here, a polynomial having a record having the same initial value associated with each of “0x96, 0x6096” and “0xFC, 0xCD13” is searched. In FIG. 4, a record in which “0x96” and “0x6096” are associated with each other and a record in which “0xFC” and “0xCD13” are associated are underlined. In FIG. 4, the initial value “95FA” of the polynomial “0x1001” is duplicated. As a result, the decryption server 20 can know the polynomial used by the digital broadcast receiver 10 and the encryption key that is the initial value.

  The decryption unit 204 uses the polynomial and the initial value searched by the search unit 203 to calculate the encrypted data group transmitted by the digital broadcast receiver 10, that is, calculated by the generation unit 103 of the digital broadcast receiver 10. 0x7197, 0xDC12, ... "is decoded (step 508). In FIG. 4, since the input values associated with the polynomial “0x1001”, the initial value “95FA”, and the generated values “0x7197, 0xDC12...” Are “97, FB. , FB... Are recognized as data before being encrypted.

  According to the present invention described above, the encrypted data can be decrypted without exchanging the encryption key between the server and the terminal.

  In the first embodiment, the digital broadcast receiver has been described. However, the present invention is not limited to the digital broadcast receiver. Any terminal can be used as long as it can receive an instruction description and a polynomial of a one-way function executed by its own device via a broadcast wave and transmit an input value, a generated value, and an encrypted data group via a communication line.

<Second Embodiment>
In the first embodiment, the operation in which the digital broadcast receiver 10 transmits two sets of input values and generated values and the encrypted data group to the decryption server 20 at the same time has been described. However, an operation of sending a plurality of generated values as an encrypted data group after sending two sets of input values and generated values first and authenticating an encryption key composed of a polynomial and an initial value may be performed. In the present embodiment, an operation of sending an encrypted data group after sending and authenticating two sets of input values and generated values first will be described. In the following description, since the operation is different from that of the first embodiment, only the operation is described, and the detailed description of the configuration is omitted.

(Operation)
The operation of this embodiment will be described. In the following description, it is assumed that a plurality of polynomials that can be used from the broadcast station 30 to the digital broadcast receiver 10 are transmitted by data broadcasting via a broadcast wave and stored in the memory 102. Further, it is assumed that an initial value to be similarly used is generated by the random number generation unit 104 and stored in the memory 102. In the following description, as in the description of the operation of the first embodiment, the case where the input value is hexadecimal 2 digits, the initial value is hexadecimal 4 digits, and the polynomial is hexadecimal 4 digits is used. However, it is not necessary to limit the decimal number and the number of digits to these.

  The generation unit 103 of the digital broadcast receiver 10 selects one polynomial and an initial value used in the hash function from the memory 102 (step 601). Here, it is assumed that the polynomial “0x1001” and the initial value “0x95FA” are selected.

  The generation unit 103 randomly extracts two different input values generated by the random number generation unit 104 (step 602). Here, it is assumed that “0x96” and “0xFC” are extracted.

  The input values “0x96” and “0xFC” are given to the hash function composed of the selected polynomial “0x1001” and the initial value “0x95FA” to generate respective generated values (step 603). It is assumed that the generated value generated here is the generated value “0x6096” for the input value “0x96” and the generated value “0xCD13” for the input value “0xFC”.

  The network side transmitting / receiving unit 105 transmits two sets of input values and generated values to the decoding server 20 (step 604). The two sets of input values and generated values transmitted here are “0x96, 0x6096” and “0xFC, 0xCD13”.

  The transmitting / receiving unit 201 of the decoding server 20 receives two sets of input values and generated values from the digital broadcast receiver 10 (step 605). Two sets of input values and generated values received here are “0x96, 0x6096” and “0xFC, 0xCD13”.

  The search unit 203 uses the received two sets of input values and generated values, and in the database, the polynomials associated with the received two sets of input values and generated values and the initial values overlap each other. And an initial value are searched (step 606). Here, a polynomial having a record having the same initial value associated with each of “0x96, 0x6096” and “0xFC, 0xCD13” is searched. In FIG. 4, a record in which “0x96” and “0x6096” are associated with each other and a record in which “0xFC” and “0xCD13” are associated are underlined. In FIG. 4, the initial value “95FA” of the polynomial “0x1001” is duplicated. Thereby, the decryption server 20 can know the encryption key composed of the polynomial and the initial value used by the digital broadcast receiver 10.

  The search unit 203 manages the searched polynomial and initial value in a temporary memory (not shown) in association with an ID that is valid only once (step 607).

  The transmission / reception unit 201 transmits this ID to the digital broadcast receiver (step 608). Even if information is intercepted during the transmission of the ID, only the ID leaks, and there is no problem because the encryption key consisting of the polynomial and the initial value is not specified.

  The transmission / reception unit 105 on the network side of the digital broadcast receiver 10 receives the ID from the decryption server 20, and divides the ID, CHKDIGIT, and the data into two hexadecimal digits and gives the hash function to the encrypted data group generated. And transmitted to the decryption server (step 609). Here, it is assumed that the encrypted data group is “0x7197, 0xCD13,...”. Further, CHKDIGIT is a set of an input value selected at random to check illegal use of an ID and a generated value calculated by giving the input value to a hash function. Even if the information to be transmitted here is intercepted, only the ID, CHKDIGIT, and encrypted data group are known, and the polynomial and initial value used to derive them are not specified.

  The transmission / reception unit 201 of the decryption server 20 receives the ID, CHKDIGIT, and the encrypted data group “0x7197, 0xCD13,...”, And the search unit 203 has a polynomial associated with the ID managed in the temporary memory. An initial value is specified (step 610).

  Next, the search unit 203 reads the generated value from the CHKDIGIT included in the received data, reads the input value specified by the polynomial, the initial value, and the generated value of the CHKDIGIT from the database 202 and matches the input value of the CHKDIGIT. The received data is determined to have been transmitted from a genuine digital broadcast receiver that is not impersonated, and the encrypted data included in the received data is decrypted using the specified polynomial and initial value (step 611). Here, when receiving an ID that is not managed in the temporary memory, the search unit 203 determines that the spoofing has been transmitted. Further, when the input value specified from the database 202 by the polynomial associated with the ID, the initial value, and the generated value of CHKDIGIT does not match the input value of CHKDIGIT, or the polynomial and initial value associated with the ID If the input values associated with the encrypted data group cannot be identified from the database 202, it is determined that the spoofed transmission has been performed.

  When the decryption is completed, the search unit 203 of the decryption server treats this ID as invalid in order to prevent unauthorized use of the ID.

  According to the present embodiment, the encrypted data can be decrypted without exchanging the encryption key between the server and the terminal.

<Third Embodiment>
In the first and second embodiments, two sets of input values and generated values and the encrypted data group are transmitted from the digital broadcast receiver 10 to the decryption server 20 via the Internet. There may be a case where the machine 10 is not connected to the Internet. Therefore, in the present embodiment, a configuration in which encrypted data is transmitted to the decryption server 20 using a mobile terminal will be described. In addition, the same number is demonstrated about the structure similar to the said embodiment, and detailed description is abbreviate | omitted.

  In the present embodiment, as shown in FIG. 7, the mobile terminal 40 is further connected to the Internet. It is assumed that the mobile terminal 40 has a function of reading a two-dimensional barcode such as a QR code (registered trademark).

  As shown in FIG. 8, the digital broadcast receiver 10 further includes a two-dimensional code image generation unit 107.

  The broadcast station 30 transmits a command description for causing the digital broadcast receiver 20 to execute the generation of the two-dimensional code image data by data broadcasting via a broadcast wave. The two-dimensional code image generation unit 107 of the digital broadcast receiver 20 converts two sets of input values, generated values, and encrypted data groups into two-dimensional code data based on the received instruction description, and generates two-dimensional code data. Is generated by combining the material image patterns. The digital broadcast receiver 20 displays the generated two-dimensional code image on the screen.

  Here, as a material image pattern for generating a two-dimensional code image, a total number of n (n = 6, 7, 8, 9) cells is one material, and all 2 n black and white binary values are used. A material image pattern representing a two-dimensional array pattern is used. Note that a cell is a white or black square image constituting a two-dimensional code image.

Examples of the material include, for example, 1 cell × 6 cell, 1 cell × 7 cell, 1 cell × 8 cell, 1 cell × 9 cell horizontally long material, 2 cell × 3 cell, 3 cell × 3 cell material. is there. In the case of the material of 1 cell × 6 cells, there are 2 ⁶ = 64 material image patterns, and in the case of the material of 1 cell × 7 cells, there are 2 ⁷ = 128 material image patterns. In the case of a material of × 8 cells, there are 2 ⁸ = 256 material image patterns, and in the case of a material of 1 cell × 9 cells, there are 2 ⁹ = 512 material image patterns.

  1 cell x 6 cell, 1 cell x 7 cell, 1 cell x 8 cell, 1 cell x 9 cell horizontally long material is the 2D code data that is the source of the 2D code, and the corresponding material image pattern When the image is replaced with the next image, the data can be divided into horizontally long cells from the beginning of the data. Therefore, the processing load on the receiver side is larger than the material image pattern of 2 cells × 3 cells, 3 cells × 3 cells. Can be reduced.

  FIG. 9 shows an example of a material image pattern of 1 cell × 9 cells. The material image pattern is composed of file name information and image data. The image data is an aggregate of binary pixel data (white pixels or black pixels) combined.

  In the example of FIG. 9, white cells or black cells are arranged in 1 cell × 9 cells, and file names associated with the values of the arranged binary pixels are given. For example, if the value of the white cell is “1” and the value of the black cell is “0”, since the first material image pattern has nine white cells arranged, the file name Is “111111111.png”. Since the second image pattern has black cells arranged only at the beginning, the file name is “0111111111.png”. Then, 512 such material image patterns are prepared.

  Next, the two-dimensional code data converted from the two sets of input values and generated values and the encrypted data group are replaced with the corresponding material image pattern images. For example, if the two-dimensional code data is “0111111111”, the two-dimensional code data “0111111111” is an image with the file name “0111111111.png” “black, white, white, white, white, white, white, white, white , White ”. This process is performed until all the cells of the two-dimensional code image are filled, and a two-dimensional code image is generated.

  FIG. 10 is a diagram showing an example of a 4 type two-dimensional code image (33 cells × 33 cells). In the case of a 4 type two-dimensional code image, a material image pattern of 1 cell × 9 cells is used and is filled with images of a total of 132 material image patterns, 33 in the row direction and 4 in the column direction. . Two-dimensional code data “000000100” corresponding to (9 rows, 1 column) to (9 rows, 9 columns) of the two-dimensional code data is “black,” which is an image of the file name “000000100.png” of the material image pattern. Replace with "black, black, black, black, black, white, black, black".

  In the case of a 4 type two-dimensional code image (33 cells × 33 cells), there are only 33 cells per side, and there is no two-dimensional code data in the 34th cell, 35th cell and 36th cell. If four material image pattern images are arranged in the row direction, three cells are left (9 cells × 4 cells−33 cells = 3 cells). Therefore, the last material image pattern in the row direction is a material image pattern in which the last three cells are “white”. For example, in the example of FIG. 10, the two-dimensional code data “000000” corresponding to (1 row, 28 columns) to (1 row, 33 columns) is used, and this two-dimensional code data “000000” is changed to “00000011”. And “black, black, black, black, black, black, white, white, white”, which is an image of “00000011.png”.

  When the QR code image is created by the digital broadcast receiver from the two sets of input values and generated values and the encrypted data group and displayed on the display screen by the method described above, the camera of the portable terminal 40 reads the QR code. As a result, two sets of input values, generated values, and an encrypted data group are transmitted to the decryption server 20.

  According to the present embodiment, even if the digital broadcast receiver 10 is not connected to the Internet, the encrypted data generated by the digital broadcast receiver can be decrypted by the decryption server without exchanging the encryption key.

<Fourth embodiment>
In the first to third embodiments, the configuration in which the digital broadcast receiver 10 receives a polynomial through a broadcast wave has been described. In the present embodiment, a configuration will be described in which a plurality of polynomials are received from an authentication server provided on the Internet via a communication line.

  In the present embodiment, as shown in FIG. 11, a terminal 50 is provided instead of the digital broadcast receiver 10. The terminal 50 is, for example, a smart TV or a mobile terminal. Further, an authentication server 60 is provided instead of the broadcasting station 30. The terminal 50, the decryption server 20, and the authentication server 60 are connected to each other via the Internet.

(Terminal)
As illustrated in FIG. 12, the terminal 50 has a configuration that does not include the broadcast-side transmission / reception unit 101 as compared to the digital broadcast receiver 10 described above.

  In the present embodiment, a program in which an instruction execution command statement is described as a hash function is received from an arbitrary public server provided on the Internet by the network side transmission / reception unit 105 of the terminal 50 or stored in the terminal 50 in advance. ing. In addition, the instruction description declares the decimal number and the number of digits of the input value, and the decimal number and the number of digits of the input value used in the terminal 50 are determined in advance. Further, in order to change a plurality of polynomials that can be used for the hash function at every predetermined time, a command statement for transmitting a transmission request for the plurality of polynomials to the authentication server 60 every predetermined time is described. . In this description, a case where a plurality of polynomials are transmitted from the authentication server 60 will be described. However, they may be received from an arbitrary server on the network or stored in the terminal 50 in advance.

(Authentication server)
In response to a transmission request from the terminal 50, the authentication server 60 transmits a plurality of polynomials that can be selected by the terminal 50.

(Operation)
Since the operation of this embodiment is the same as that of the above embodiment, a detailed description thereof is omitted. Note that this embodiment may be applied to any of the first to third embodiments.

  According to the present embodiment, the encrypted data can be decrypted without exchanging the encryption key between the server and the terminal.

  The terminal of the present invention described above can be configured by hardware as is apparent from the above description, but can also be realized by a computer program.

  The terminal has a processor and a program memory, and realizes functions and operations similar to those of the above-described embodiment by a processor that operates with a program stored in the program memory. Note that only a part of the functions of the above-described embodiment can be realized by a computer program.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not necessarily limited to the above-described embodiments and examples, and various modifications can be made within the scope of the technical idea. I can do it.

10 Digital Broadcasting Receiver 20 Decoding Server 30 Broadcasting Station 40 Mobile Terminal 50 Terminal (Mobile Terminal, Smart TV)
60 Authentication server

Claims (7)

A cryptographic system,
Generated values generated by giving different input values to each one-way function obtained by applying multiple initial values to each of the polynomials that are symmetric between the input value and the generated value, and for generating this generated value A database in which used input values, initial values, and polynomials are stored in association with each other;
The unidirectionality used to generate a generated value from each input value by giving different input values to a unidirectional function obtained by applying an arbitrary initial value to an arbitrary polynomial in the polynomial. Generating means for generating encrypted data by giving, as an input value, data divided according to the number of digits of the input value to the function;
Based on a plurality of sets of generated values and input values that have been transmitted, the polynomials and initial values associated with the plurality of generated values and input values that have been transmitted in the database overlap. A search means for searching for a polynomial and an initial value;
A decoding unit that decrypts the encrypted data by reading out the generated value associated with the polynomial and the initial value searched by the searching unit and the encrypted data generated by the generating unit from the database; Feature cryptographic system. The generation means selects an arbitrary polynomial from polynomials changed at a predetermined time set according to the number of digits of the input value,
2. The cryptographic system according to claim 1, wherein the search means checks whether the searched polynomial is one of the polynomials changed at the predetermined time.   The cryptographic system according to claim 1 or 2, wherein the generation unit selects an arbitrary polynomial from among polynomials transmitted via broadcast waves.   The cryptographic system according to claim 1 or 2, wherein the generation unit selects an arbitrary polynomial from among polynomials transmitted via a communication line. A decryption server for decrypting encrypted data,
Generated values generated by giving different input values to each one-way function obtained by applying multiple initial values to each of the polynomials that are symmetric between the input value and the generated value, and for generating this generated value A database in which used input values, initial values, and polynomials are stored in association with each other;
A generated value generated from each input value by giving a different input value to a one-way function obtained by applying an arbitrary initial value to an arbitrary polynomial in the polynomial, and the generated value Based on the given input value, a search is made for a polynomial and an initial value in which the polynomial and the initial value associated with the plurality of generated values and input values transmitted in the database overlap each other. Search means;
The search means searches for encrypted data generated by giving, as an input value, data that is divided according to the number of digits of the input value to the one-way function used to generate the generated generated value. A decryption server comprising decryption means for decrypting the encrypted data by reading out a generated value associated with a polynomial and an initial value from the database. An encryption method,
A generated value is generated from each input value by giving a different input value to a one-way function in which an arbitrary initial value is applied to an arbitrary polynomial in a polynomial symmetric between the input value and the generated value. Generation value generation step;
A dividing step of dividing data according to the number of digits of the input value;
An encrypted data generating step for generating encrypted data by giving the data divided in the dividing step as an input value to the one-way function used for generating the generated value in the generated value generating step;
Based on a plurality of sets of generated values and input values that have been transmitted, each unidirectional function is formed by applying a plurality of initial values to each of the polynomials that are symmetric between the input value and the generated value. A plurality of generated values transmitted in a database in which generated values generated by giving different input values, and input values, initial values, and polynomials used to generate the generated values are stored in association with each other; A search step for searching for a polynomial and an initial value in which a polynomial associated with the input value and the initial value overlap each other; and
A decryption step of decrypting the encrypted data by reading out the generated value associated with the polynomial and the initial value searched in the searching step and the encrypted data generated in the generated value generating step from the database; An encryption method comprising: A decryption program of a decryption server for decrypting encrypted data, the decryption program comprising:
A generated value generated from each input value by giving a different input value to a one-way function obtained by applying an arbitrary initial value to an arbitrary polynomial in a polynomial symmetric between the input value and the generated value , Receiving the input value given in generating the generated value, and, based on the generated generated value and the input value, a plurality of initial values for each of the polynomials having symmetry between the input value and the generated value. A database in which generated values generated by applying different input values to each one-way function to which values are applied, and input values, initial values, and polynomials used to generate the generated values are stored in association with each other A search means for searching for a polynomial and an initial value, each of which is overlapped with an initial value and a polynomial associated with the plurality of generated values and input values transmitted in
The search means searches for encrypted data generated by giving, as an input value, data that is divided according to the number of digits of the input value to the one-way function used to generate the generated generated value. A decryption program that functions as decryption means for decrypting encrypted data by reading a generated value associated with a polynomial and an initial value from the database.

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