Communication server, communication method, and communication program

Abstract

To provide a communication system capable of realizing secure communication between mobile carriers having resistance against aggression using a quantum computer in mobile communication.SOLUTION: A communication server 1 comprises: a first encryption processing part 11 that encrypts a sharing key with a communications partner as a first value by a quantum resistant public key cryptography, and generates first encryption data; a second encryption processing part 12 that encrypts a second value by using the other public key cryptography and generates second encryption data; a synthesis processing part 13 that generates synthesis encryption data by an AONT by using the first and second encryption data as an input; a key sharing part 14 that transmits the synthesis encryption data to the communications partner, and decodes and shares the sharing key; and a communication processing part 15 that performs encryption data communication with the communications partner by a TSL-PSK protocol using the sharing key.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a secure communication method for connecting communication carriers in mobile communication.

Background Art

[0002] Conventionally, in mobile communication using mobile phones and smartphones, etc., for a roaming service that connects communication carriers, a security protection server (SEPP: Security Edge Protection Proxy) is installed in the part of the mutual connection of the communication carrier networks. Between SEPPs, in order to perform communication that requires security (secure communication), functions such as authentication of a communication partner, encryption of communication content, and detection of tampering are provided by a protocol called TLS (Transport Layer Security) (for example, see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=3,7]]However, there was concern about the resistance of the public key cryptosystem used by TLS against attacks using quantum computers.

[0005] An object of the present invention is to provide a communication system that can realize secure communication between communication carriers that has resistance against attacks using quantum computers in mobile communication. [Means for solving the problem]

[0006] The communication server according to the present invention comprises: a first encryption processing unit that encrypts a shared key with a communication partner as a first value using a post-quantum public-key cryptography scheme to generate first encrypted data; a second encryption processing unit that encrypts a second value using a public-key cryptography scheme different from the post-quantum public-key cryptography scheme to generate second encrypted data; a synthesis processing unit that generates synthesized encrypted data by AONT (All-Or-Nothing Transformation) using the first encrypted data and the second encrypted data as inputs; a key sharing unit that transmits the synthesized encrypted data to the communication partner and decrypts and shares the shared key using AONT and the post-quantum public-key cryptography scheme; and a communication processing unit that communicates encrypted data with the communication partner using the TSL-PSK (Transport Layer Security pre-shared key ciphersuites) protocol with the shared key.

[0007] The second value may be a random number.

[0008] The second value may be the same as the first value.

[0009] The second value may include information about the expiration date of the shared key.

[0010] The synthesis processing unit may combine a predetermined bit sequence with either the first encrypted data or the second encrypted data to make their lengths the same.

[0011] The key sharing unit may divide and transmit the synthesized encrypted data.

[0012] The communication method according to the present invention relates to a communication system equipped with communication servers for each network to connect the networks of telecommunications carriers to each other. In this system, one communication server encrypts a shared key with the other communication server as a first value using a post-quantum public-key cryptography scheme to generate first encrypted data, encrypts a second value using a public-key cryptography scheme different from the post-quantum public-key cryptography scheme to generate second encrypted data, generates composite encrypted data using AONT (All-Or-Nothing Transformation) with the first encrypted data and the second encrypted data as input, transmits the composite encrypted data to the other communication server, decrypts the shared key from the received composite encrypted data using AONT and the post-quantum public-key cryptography scheme and shares it with the one communication server, and the one communication server and the other communication server communicate encrypted data to each other using the TSL-PSK (Transport Layer Security pre-shared key ciphersuites) protocol with the shared key.

[0013] The communication program according to the present invention is for causing a computer to function as the aforementioned communication server. [Effects of the Invention]

[0014] According to the present invention, secure communication between telecommunications carriers can be realized in mobile communications, which is also resistant to attacks using quantum computers. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram shows the configuration for realizing secure communication between telecommunications carriers in the embodiment. [Figure 2] This figure shows the functional configuration of the communication server in the embodiment. [Figure 3] This figure illustrates the processing procedure by which a communication server in an embodiment generates synthesized encrypted data using AONT. [Figure 4]It is a sequence diagram showing the procedure of pre-shared key in the embodiment.

Mode for Carrying Out the Invention

[0016] Hereinafter, an example of an embodiment of the present invention will be described. The communication system of this embodiment is a system that includes a SEPP for mutually communicating and connecting between networks of communication carriers in mobile communication for each network. In this embodiment, when establishing a roaming connection between communication carriers, the protocol between SEPPs for establishing secure communication for privacy protection is conventionally changed.

[0017] FIG. 1 is a diagram showing a configuration for realizing secure communication between communication carriers in this embodiment. The communication method of this embodiment changes the conventional encrypted communication by TLS (Transport Layer Security) between SEPPs installed in the networks of different communication carriers A and B to TLS-PSK (pre-shared key ciphersuites) using a pre-shared key. Then, the SEPP pre-shares this shared key using a quantum-resistant public key cryptosystem such as CRYSTALS-Kyber. At this time, by combining a plurality of encryption methods and synthesizing encrypted data by AONT (All-Or-Nothing Transformation), the security is enhanced.

[0018] FIG. 2 is a diagram showing the functional configuration of the communication server 1 in this embodiment. The communication server 1 is an information processing device (computer) including a control unit 10, a storage unit 20, and a communication device, etc., and constitutes a security protection server (SEPP) for connecting (roaming) between networks of communication carriers.

[0019] The control unit 10 controls the entire communication server 1 and realizes each function in the present embodiment by appropriately reading and executing various programs stored in the storage unit 20. The control unit 10 may be a CPU. Moreover, the storage unit 20 is a storage area for various programs and various data for causing the hardware group to function as the communication server 1, and may be a ROM, a RAM, a flash memory, a hard disk drive (HDD), or the like.

[0020] The control unit 10 includes a first encryption processing unit 11, a second encryption processing unit 12, a synthesis processing unit 13, a key sharing unit 14, and a communication processing unit 15.

[0021] The first encryption processing unit 11 encrypts a shared key (first value) to be shared with the communication server 1A of the destination network, which is the communication partner, using the public key of the communication server 1A by a quantum-resistant public key encryption method, and generates first encrypted data.

[0022] The second encryption processing unit 12 encrypts a second value using the public key of the communication server 1A by another public key encryption method different from the quantum-resistant public key encryption method of the first encryption processing unit 11, and generates second encrypted data. Note that the public key encryption method used by the second encryption processing unit 12 is not limited to the quantum-resistant public key encryption method, and may be a conventional public key encryption method. Also, the second encryption processing unit 12 may generate a plurality of second encrypted data by a plurality of encryption methods.

[0023] Here, the second value to be encrypted may be, for example, a random number. Alternatively, the second value may be common with the first value in order to compare and verify with the decrypted first value. Also, the second value may include validity period information of the shared key (for example, validity period and current time). In this case, in the process of key sharing by the key sharing unit 14, key sharing is performed only when the conditions based on the validity period information decrypted together with the shared key are satisfied.

[0024] The synthesis processing unit 13 takes the first encrypted data and the second encrypted data as input and generates synthesized encrypted data using AONT. If it is required that the sizes of multiple input data to AONT be the same, or if the data length is specified, the synthesis processing unit 13 may align the lengths of either the first encrypted data or the second encrypted data by concatenating a predetermined bit sequence (for example, by appending "10000..." to the end).

[0025] Figure 3 illustrates the processing procedure by which the communication server 1 generates composite encrypted data using AONT in this embodiment.

[0026] Here, the first encrypted data is a ciphertext encrypted using a quantum-resistant public-key cryptography scheme (for example, a shared key encrypted with algorithm A), and the second encrypted data is a ciphertext encrypted using another public-key cryptography scheme (for example, a shared key encrypted with algorithm B) or its calculated value (for example, a hash value).

[0027] For AONT, the first encrypted data and the second encrypted data are input. The first encrypted data is masked (e.g., by an XOR operation) by the second encrypted data, which is padded with "0" or the like (Expansion function), and becomes the most significant bit (A) of the output. Furthermore, the second encrypted data is masked (for example, by an XOR operation) by the hash value of (A), becoming the lower bits of the output (B). Furthermore, in the case of post-quantum public-key cryptography, the size of the ciphertext is larger than in conventional cryptography, with at least the most significant bits (A) of the output being several thousand bits long.

[0028] The key sharing unit 14 sends synthesized encrypted data to the communication server 1A, which is the communication partner, in order to pre-share the key to be used in TLS-PSK. As mentioned above, the size of the composite encrypted data generated using the quantum-resistant public-key cryptography scheme is large, so the key sharing unit 14 divides the composite encrypted data and transmits it. Furthermore, when the key sharing unit 14 receives synthesized encrypted data from another communication server 1B, it decrypts the shared key using a method common to the sender (AONT and post-quantum public-key cryptography).

[0029] The communication processing unit 15 performs encrypted data communication with the communication partner using the TSL-PSK protocol with a pre-shared shared key.

[0030] Figure 4 is a sequence diagram showing the procedure for pre-key sharing in this embodiment. This example illustrates a case where a key is shared between one communication server (SEPP) (A) and another communication server (SEPP) (B) in response to a request from the first communication server (SEPP) (A).

[0031] In step S1, communication server (A) sends a connection request to communication server (B) accompanied by a public key certificate. In step S2, the communication server (B) encrypts the shared key using the public key contained in the received public key certificate, that is, generates the aforementioned synthesized encrypted data.

[0032] In step S3, the communication server (B) sends the encrypted shared key, i.e., the generated composite encrypted data, to the requesting communication server (A). In step S4, the communication server (A) decrypts the shared key from the received composite encrypted data using the private key corresponding to the public key in step S2. Subsequently, communication server (A) and communication server (B) establish a communication connection through a TSL-PSK handshake and begin encrypted data communication.

[0033] According to this embodiment, the communication server 1 receives as input first encrypted data, in which the shared key with the communication partner is encrypted using a quantum-resistant public-key cryptography scheme, and second encrypted data, in which the second value is encrypted using another public-key cryptography scheme, and generates composite encrypted data using AONT. The communication server 1 sends this composite encrypted data to the communication partner for decryption and sharing. Therefore, communication server 1 can securely share keys in advance and then communicate encrypted data with its communication partner while adhering to the standard specifications of the TSL protocol. As a result, secure communication between telecommunications carriers will be realized in mobile communications, which will also be resistant to attacks using quantum computers.

[0034] The communication server 1 may equalize the length of each encrypted data by concatenating a predetermined bit sequence for multiple inputs to AONT, thereby reducing the processing load on AONT.

[0035] By using a quantum-resistant public-key cryptography scheme, communication server 1 will transmit longer synthetic encrypted data than conventional encryption methods. However, by dividing and transmitting this data, it can securely share the key only with communication partners who correctly receive all of it.

[0036] The communication server 1 can use a random number or a value calculated based on a random number (for example, the hash value of the ciphertext) as the second encrypted data to be combined with the first encrypted data, thereby simplifying the process of generating the combined encrypted data.

[0037] Communication server 1 may use the same second value (shared key) as the first value, which is the basis for the second encrypted data. This allows communication server 1 to compare and verify both the first and second values ​​by decrypting them, or by encrypting the decrypted first value in the same way as the second value, and determine whether or not tampering has occurred.

[0038] Communication server 1 may include shared key expiration information in the second value, thereby enabling encrypted communication using a shared key that is valid only for an appropriate period, and suppressing attacks such as shared key reuse.

[0039] Furthermore, according to this embodiment, for example, privacy risks in mobile communications are reduced, which makes it possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0040] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. Furthermore, the effects described in the embodiments described above are merely a list of the most preferred effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0041] The communication method provided by communication server 1 is implemented by software. When implemented by software, the programs constituting this software are installed on an information processing device (computer). These programs may be distributed to users by being recorded on removable media such as a CD-ROM, or by being downloaded to the user's computer via a network. Furthermore, these programs may be provided to the user's computer as a web service via a network without being downloaded. [Explanation of symbols]

[0042] 1, 1A, 1B Communication Servers 10 Control Unit 11. First Encryption Processing Unit 12 Second Encryption Processing Unit 13 Synthesis Processing Unit 14 Key sharing part 15 Communication Processing Unit 20 Memory section

Claims

1. A first encryption processing unit generates first encrypted data by encrypting it using a quantum-resistant public-key cryptography scheme with a shared key with the communication partner as the first value, A second encryption processing unit that encrypts the second value using a public-key cryptography scheme different from the aforementioned quantum-resistant public-key cryptography scheme and generates second encrypted data, A synthesis processing unit that takes the first encrypted data and the second encrypted data as input and generates synthesized encrypted data by AONT (All-Or-Nothing Transformation), A key sharing unit that transmits the synthesized encrypted data to the communication partner and decrypts and shares the shared key using the AONT and the post-quantum public-key cryptography scheme, A communication server comprising a communication processing unit that performs encrypted data communication with the communication partner using the TSL-PSK (Transport Layer Security pre-shared key ciphersuites) protocol with the aforementioned shared key.

2. The communication server according to claim 1, wherein the second value is a random number.

3. The communication server according to claim 1, wherein the second value is the same as the first value.

4. The communication server according to claim 1, wherein the second value includes the expiration date information of the shared key.

5. The communication server according to claim 1, wherein the synthesis processing unit combines a predetermined bit sequence with either the first encrypted data or the second encrypted data to make their lengths equal.

6. The key sharing unit is a communication server according to claim 1, which divides and transmits the composite encrypted data.

7. In a communication system equipped with a communication server for each network to connect the networks of telecommunications carriers, One of the communication servers, Using the shared key with the other communication server as the first value, the data is encrypted using a quantum-resistant public-key cryptography scheme to generate the first encrypted data. The second value is encrypted using a public-key cryptography scheme different from the quantum-resistant public-key cryptography scheme, and the second encrypted data is generated. Using the first encrypted data and the second encrypted data as input, composite encrypted data is generated by AONT (All-Or-Nothing Transformation). The synthesized encrypted data is transmitted to the other communication server. The other communication server is, The shared key is decrypted from the received synthetic encrypted data using the AONT and the post-quantum public-key cryptography scheme and shared with the one communication server. A communication method in which one communication server and the other communication server communicate encrypted data to each other using the TSL-PSK (Transport Layer Security pre-shared key ciphersuites) protocol with the shared key.

8. A communication program for causing a computer to function as a communication server according to any one of claims 1 to 6.

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