Car sharing system, sharing method, in-vehicle server device and program

Abstract

Provided are a car-sharing system, a sharing method, a vehicle-mounted server device, and a program which contribute to prevent identity theft through the leakage of a biological feature amount stored in a vehicle-mounted device in the car-sharing system. The car-sharing system comprises: a vehicle-mounted server device which includes a registration unit through which ciphertext data obtained by encrypting biological information about a service scheduled user is registered, an encryption unit which, in order to authenticate a service use subscriber, encrypts the biological information about service use subscribers and takes the encrypted information as encrypted authentication query data, and a collation unit which collates the registered ciphertext data with the encrypted authentication query data in a state where both the pieces of data are encrypted; and a user device which includes a determination unit which determines, on the basis of the collation result from the collation unit, whether the collation result is within an acceptance range of authentication.

Description

Technical Field

[0001] The present invention relates to a car-sharing system, a sharing method, an in-vehicle server device, and a program.

Background Art

[0002] In recent years, the popularity of car-sharing services that enable users to easily borrow vehicles has been remarkable. In a car-sharing service, a user accesses a server on the service side from a user terminal such as a smartphone in advance to make a reservation. After the reservation is completed, reservation information and the user's authentication information are sent from the server to an in-vehicle device installed in the shared vehicle, and the user can go to the vehicle, authenticate, unlock the vehicle, and use the vehicle.

[0003] Patent Document 1 discloses an invention of a user authority authentication system using biometric information applicable to car-sharing. In this invention, a user's biometric feature amount encrypted with a user public key is stored in an in-vehicle device. The user ID card stores the user's secret key information. The car-sharing system sends the user's secret key information to the in-vehicle device by reading the user ID card with a reader installed in the vehicle at the time of use. At the same time, the user's biometric information is acquired, the encrypted biometric feature amount stored in the in-vehicle device is decrypted using the user's secret key information, and authentication is performed by comparing the acquired biometric information to obtain the user's authentication result.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Note that each disclosure of the above prior art documents is incorporated herein by reference. The following analysis is made by the present inventors.

[0006] In the invention described in Patent Document 1, the user's private key is passed to the in-vehicle device, which is the service provider, creating a threat that a malicious actor could steal the user's private key. This could lead to threats such as unauthorized intrusion into the in-vehicle network, the extraction of information stored in the in-vehicle device during vehicle inspections, or access to information remaining in the in-vehicle device when the vehicle is traded in or otherwise transferred to another party, allowing the decryption of biometric data stored in the in-vehicle device and the leakage of plaintext biometric data. If plaintext biometric data is leaked, other services that use biometric authentication may also suffer damage such as impersonation.

[0007] Therefore, the object of the present invention is to provide a car-sharing system, an in-vehicle server device, a sharing method, and a program that contribute to preventing impersonation due to the leakage of biometric data stored in an in-vehicle device in a car-sharing system. [Means for solving the problem]

[0008] A car-sharing system is provided that includes an in-vehicle server device having: a registration unit for registering registration ciphertext data in which the biometric information of a prospective service user is encrypted; an encryption unit for authenticating a service user by encrypting the biometric information of the service user to obtain encrypted authentication query data; a matching unit for matching the registration ciphertext data and the encrypted authentication query data while both are encrypted; and a determination unit for determining whether or not the authentication is within the acceptable range based on the matching result of the matching unit.

[0009] A sharing method is provided that includes the steps of: registering registration ciphertext data in which the biometric information of a prospective service user is encrypted; encrypting the biometric information of a service user to obtain encrypted authentication query data in order to authenticate the service user; comparing the registration ciphertext data and the encrypted authentication query data in an encrypted state; and determining whether or not the authentication is within the scope of acceptance based on the comparison result.

[0010] According to a third aspect of the present invention and disclosure, an in-vehicle server device is provided, comprising: a registration unit for registering registration ciphertext data in which the biometric information of a prospective service user is encrypted; an encryption unit for authenticating a service user by encrypting the biometric information of the service user to obtain encrypted authentication query data; and a matching unit for comparing the registration ciphertext data and the encrypted authentication query data while both are encrypted.

[0011] A fourth aspect of the present invention and disclosure is provided, which causes a computer to perform the following processes: registering registration ciphertext data in which the biometric information of a prospective service user is encrypted; encrypting the biometric information of a service user to authenticate the service user and converting it into encrypted authentication query data; and comparing the registration ciphertext data and the encrypted authentication query data while both are encrypted. [Effects of the Invention]

[0012] From each perspective of the present invention and disclosure, the present invention provides a car-sharing system, a sharing method, an in-vehicle server device, and a program that contribute to preventing impersonation due to the leakage of biometric data stored in an in-vehicle device in a car-sharing system. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram illustrating the processing overview of a car-sharing system according to one embodiment. [Figure 2]A block diagram shows an example of the configuration of a car-sharing system according to one embodiment. [Figure 3] This is a schematic diagram illustrating the processing overview of the car-sharing system according to the first embodiment. [Figure 4] This is a block diagram showing an example of the configuration of a car-sharing system according to the first embodiment. [Figure 5] This is a schematic diagram illustrating another overview of the processing of the car-sharing system according to the first embodiment. [Figure 6] This is a block diagram showing an example of another configuration of the car-sharing system according to the first embodiment. [Figure 7] This is a flowchart showing the operation of the car-sharing system according to the first embodiment. [Figure 8] This is a schematic diagram showing the hardware configuration of the car-sharing system according to the first embodiment. [Figure 9] This is a schematic diagram illustrating the processing overview of the car-sharing system according to the second embodiment. [Figure 10] This is a block diagram showing an example of the configuration of a car-sharing system according to the second embodiment. [Figure 11] This is a flowchart illustrating the operation of the car-sharing system according to the second embodiment. [Modes for carrying out the invention]

[0014] [Summary of the process in one embodiment] First, the outline of the processing of one embodiment will be described. Note that the reference numerals of the drawings appended to this outline are for convenience and are appended to each element as an example to assist understanding, and the description of this outline is not intended to impose any limitations. Also, the connection lines between blocks in each figure include both bidirectional and unidirectional ones. For the unidirectional arrow, it schematically shows the flow of the main signal (data) and does not exclude bidirectionality. Furthermore, in the circuit diagrams, block diagrams, internal configuration diagrams, connection diagrams, etc. shown in the present disclosure, although not explicitly shown, input ports and output ports exist at the input ends and output ends of each connection line respectively. The same applies to the input / output interface.

[0015] FIG. 1 is a schematic diagram for showing the outline of the processing of a car-sharing system according to one embodiment. As shown in this figure, when a reservation user of the car-sharing service approaches a vehicle that is a shared car, a camera mounted on the vehicle captures the face of the reservation user, which is biometric information. The captured video is converted into feature amounts by preprocessing by the in-vehicle server device 10 and encrypted to be encrypted authentication query data. On the other hand, a template of a registered user is encrypted and stored as registered ciphertext data in the in-vehicle server device 10.

[0016] In the in-vehicle server device 10, the encrypted template of the registered user and the encrypted authentication query data are compared while remaining in the encrypted state. The comparison is performed by obtaining the (encrypted) distance D, which is the similarity of the feature amounts between the registered ciphertext data and the encrypted authentication query data. Since the encrypted distance D is encrypted with the public key of the user generated by a user device 11 such as a smartphone, D is sent to the user device 11 and decrypted with the secret key of the user.

[0017] The decrypted D is determined at the user device 11 whether it is within a predetermined acceptance range, and sends a message of OK or NG, which is the determination result of within the acceptance range or outside the acceptance range, to the in-vehicle server device 10. The in-vehicle server device 10 that receives the message performs controls such as, for example, unlocking the vehicle key if it is OK, or sending a message to that effect to the user device 11 and displaying it on the user device 11 if it is NG.

[0018] In this way, at the time of authentication, by encrypting the authentication query data in the in-vehicle server device and performing comparison with the registered encrypted text data while it is encrypted, the plaintext feature amount of the service reservation person stays in the storage area of the in-vehicle server device at the time of authentication, so that the threat of a malicious person illegally intruding into the in-vehicle network and stealing the biometric feature amount can be reduced.

[0019] [Configuration of an Embodiment] Next, the configuration of a car-sharing system according to an embodiment will be described using the drawings. FIG. 2 is a block diagram showing an example of the configuration of a car-sharing system according to an embodiment. As shown in this figure, a car-sharing system according to an embodiment includes an in-vehicle server device 10 having a registration unit 12, an encryption unit 13, and a collation unit 14, and a user device 11 having a determination unit 15.

[0020] Note that the configuration of the car-sharing system is not limited to only the in-vehicle server device 10 and the user device 11. For example, it may have a management server device (described later) having a registration unit for storing the registered encrypted text. Also, the in-vehicle server device 10 is not limited to one. This is because there may be a case where a plurality of reservation persons share and use a plurality of vehicles. A configuration in which there are a plurality of such in-vehicle server devices 10 is also within the scope of the present invention.

[0021] The registration unit 12 registers registration ciphertext data, which is encrypted biometric information of the prospective service user, in the in-vehicle server device 10. The encryption unit 13 encrypts the biometric information of the service user to authenticate the service user in the in-vehicle server device 10 and converts it into encrypted authentication query data. The matching unit 14 compares the registration ciphertext data and the encrypted authentication query data in the in-vehicle server device 10 while both are encrypted. The determination unit 15 determines in the user device 11 whether or not the authentication is within the acceptable range based on the matching result of the matching unit 14.

[0022] According to one embodiment of the car-sharing system, as described above, by comparing the encrypted authentication query data with the registered ciphertext data while the data remains encrypted, it is possible to reduce the time that the plaintext authentication query data remains in the storage of the in-vehicle server device. This makes it possible to avoid situations in which malicious actors could infiltrate the in-vehicle network, steal biometric data, and launch impersonation attacks.

[0023] Specific embodiments will be described in more detail below with reference to the drawings. In each embodiment, the same reference numerals are used for the same components, and their descriptions are omitted.

[0024] [First Embodiment] In the car-sharing system of the above embodiment, the in-vehicle server device encrypts the authentication query data. The encrypted authentication query data generated is encrypted with the keys of n users if there are n registered users. On the other hand, the registration ciphertext data is also encrypted with the keys of n users. Furthermore, in order to verify while the data remains encrypted, it is assumed that the data is encrypted with the same key. When a service user is photographed by a camera installed in the vehicle, the system cannot determine which key corresponds to that service user. For this reason, there are methods such as sending additional information to the system, such as a user ID card, to identify the corresponding key. However, if there are multiple service users driving and they are photographed by the camera at the same time, the handling becomes inevitably complex.

[0025] Therefore, let's consider encrypting a single biometric feature using all n keys. In this case, when a single biometric feature is obtained, n encrypted authentication query data will be generated. For example, if encryption takes 60 milliseconds, and there are 10,000 registered users of the service, the plaintext biometric feature will remain in storage for 600 seconds. This creates a threat that the in-vehicle network could be infiltrated during the time the data is in plaintext and the plaintext feature could be stolen. This threat increases as the number of service users increases.

[0026] Furthermore, if there are multiple drivers who have made reservations, the number of encryption operations required will increase by the number of drivers, creating a problem of even greater threats.

[0027] In the car-sharing system of this embodiment, n conversion keys are generated before authentication to convert the service's (public) key to each user's (public) key. When authentication query data, which is the biometric feature for authentication, is obtained, it is first encrypted with the service's (public) key, then re-encrypted with the conversion key to generate n encrypted authentication query data. Then, a comparison is performed with the registered ciphertext data. In the above case, since the biometric feature is in plaintext only for the duration of one encryption operation using the service's (public) key, the threat described above is significantly reduced.

[0028] [Summary of the process in the first embodiment] Figure 3 is a schematic diagram illustrating the processing overview of the car-sharing system according to the first embodiment. As shown in this figure, the system includes a management server device 19 in addition to the configuration of the first embodiment. The management server device 19 generates a set of a public key 31 for the service and a private key 32 for the service. In the car-sharing system of this embodiment, when the biometric features of the service reservation holder are obtained during authentication, the in-vehicle server device 10 encrypts the biometric features using the public key 31 for the service and uses them as encrypted authentication query data.

[0029] Meanwhile, the management server device 19 generates a conversion key 33 using the service's secret key 32 and the user's public key. The conversion key 33 then encrypts the encrypted biometric features generated using the service's public key 31. Specifically, the encrypted biometric features encrypted using the service's public key 31 are converted into encrypted authentication query data 35 encrypted with the user's public key without decryption. The encrypted authentication query data 35 is then compared with the registered ciphertext 36, which is also encrypted with the user's public key.

[0030] [Configuration of the first embodiment] Next, the configuration of the car-sharing system of Embodiment 1 will be described with reference to the figures. Figure 4 is a block diagram showing an example of the configuration of the car-sharing system according to this embodiment. As shown in this figure, the car-sharing system according to the first embodiment includes an in-vehicle server device 10 having a registration unit 12, an encryption unit 13, and a verification unit 14; a user device 11 having a determination unit 15 and a user key generation unit 16; and a management server device 19 having a service key generation unit 17 and a conversion key generation unit 18.

[0031] The registration unit 12 registers encrypted registration ciphertext data containing the biometric information of prospective service users in the in-vehicle server device 10. "Registration" means storing in a storage area, and in the car-sharing system of this embodiment, the registration ciphertext data is ultimately stored in the storage area of ​​the in-vehicle server device 10. Therefore, when a prospective service user registers to use the service, the encrypted biometric information may reach this unit of the in-vehicle server device 10 via the user device 11 or the management server device 19 and be stored in the storage area as registration ciphertext data.

[0032] Here, "encryption" means encrypting the biometric information of a prospective service user with a user-specific key, and includes, for example, acquiring the user's biometric information on the user device 11 and encrypting it with the user's public key.

[0033] A "prospective service user" is a person who can reserve the use of the service and who can be the driver of the vehicle. For example, a prospective service user is someone who has entered into a contract to use a car-sharing service. The prospective service user registers their biometric information in the registration unit 12. "Biometric information" is not limited to facial features but includes fingerprints, palm prints, voiceprints, retinal features, and other characteristics. The registration unit 12 may also store data such as the user's user ID and information on their driver's license, associated with the registered ciphertext data.

[0034] The encryption unit 13 encrypts the biometric information of a service user in order to authenticate the service user in the in-vehicle server device 10, and uses it as encrypted authentication query data. A "service user" is a person who plans to use the service and has made a reservation to rent a specific vehicle (shared car) at a specific date and time. A service user is a person who intends to use the vehicle. A service user can be the driver of the vehicle. The "encrypted authentication query data" is obtained when a service user rents a vehicle, by encrypting and feature-quantifying images, etc., acquired through input interfaces such as cameras installed in the vehicle or cameras equipped on the user's device, in order to compare them with registered ciphertext data.

[0035] The encryption unit 13 of the car-sharing system in this embodiment encrypts the biometric information of the service user using the public key of the service, and then re-encrypts the encrypted biometric information using a conversion key described later to obtain encrypted authentication query data.

[0036] The matching unit 14 compares the registered ciphertext data and the encrypted authentication query data in the in-vehicle server device 10 while both are encrypted. "While both are encrypted" means that the encrypted data is compared without decrypting it.

[0037] In this embodiment, homomorphic encryption and homomorphic operations are used as examples to match feature quantities while they remain encrypted. For example, an encryption scheme called Somewhat homomorphic encryption is a public-key encryption scheme that has homomorphism with respect to an arbitrary number of additions and a finite number of multiplications. In this scheme, given ciphertexts Enc(m1) and Enc(m2) of plaintexts m1 and m2, the ciphertext Enc(m1○m2) of a binary operation m1○m2 can be calculated without decrypting it back into the plaintexts m1 and m2. Here, "○" is a binary operation, such as addition "+" or multiplication "×". Such Somewhat homomorphic encryption can be applied to similarity calculations and other matching means in the matching unit 14.

[0038] The determination unit 15 determines whether the authentication is within the acceptable range based on the matching result of the matching unit 14 in the user device 11. The matching unit 14 of the in-vehicle server device 10 calculates the encryption similarity D of the feature quantities of the encrypted authentication query data and the registered ciphertext data. The determination unit 15 of the user device 11 receives this and decrypts the encryption similarity Enc(D) with the user's private key. The determination unit 15 determines whether the decrypted D is within the acceptable range, which is the numerical range in which authentication is OK.

[0039] The car-sharing system of this embodiment may have a control unit (not shown) in the in-vehicle server device 10 that receives authentication results (OK / NG) and controls the vehicle's equipment. For example, it may unlock the vehicle, power on the accessory power supply, or control various devices attached to the vehicle.

[0040] The user key generation unit 16 generates a pair of the user's public key and the user's private key in the user device 11. As described above, the user's public key is used when generating registered ciphertext data and when generating encrypted authentication query data. In addition, the determination unit 15 uses the user's private key to decrypt the encryption similarity score Enc(D) encrypted with the user's public key.

[0041] The service key generation unit 17 generates a pair of the service's public key and the service's private key in the management server device 19. The service's public key is sent to the in-vehicle server device and is used to encrypt the biometric features acquired during authentication and to process them as encrypted authentication query data. The service's private key is used to generate a conversion key in the conversion key generation unit 18, which will be described later.

[0042] The conversion key generation unit 18, in the management server device 19, uses the user's public key and the service's private key to generate a second encrypted message encrypted with the user's public key from a first encrypted message encrypted with the service's public key.

[0043] In the car-sharing system of this embodiment, the conversion key uses proxy re-encryption technology. Proxy re-encryption is a technology that can convert the ciphertext of one key to the ciphertext of a second key without obtaining the plaintext information. Here it is used to convert the public key of the management server device 19 service to the user's public key without decryption. Here, there are two types of public-key cryptography key pairs, which are represented as (public key 1, private key 1) = (pk1, sk1) and (public key 2, private key 2) = (pk2, sk2). To perform proxy re-encryption, a conversion key is generated. If the conversion key is ReKey, the conversion key generation process rk = ReKeyGen() becomes ReKeyGen(pk2, sk1) = rk1 → 2. Here, pk2 is the public key of the second (destination) ciphertext, and sk1 is the private key of the first (source) ciphertext.

[0044] In proxy re-encryption technology, there are methods where the conversion key can be converted in one direction as described above, as well as methods where it can be converted in both directions. In the latter case, both the source and destination secret keys are required, as shown in ReKeyGen(sk1,sk2)=rk1←→2. In the car-sharing system of this embodiment, it becomes necessary to deliver the user's secret key from the user device 11 to the management server device 19, which raises security issues, so it is desirable to adopt the aforementioned one-way conversion model. If the feature quantity of the plaintext before encryption is M, the processing of the conversion key can be expressed as ReEnc(rk1→2,Enc(pk1,M))=Enc(pk2,M).

[0045] [Another overview of the process in the first embodiment] Figure 5 is a schematic diagram illustrating another overview of the processing of the car-sharing system according to the first embodiment. The difference from the above [Overview of Processing in the First Embodiment] is that the matching process and the conversion process using the conversion key are performed by the management server device 19. The communication between the user device 11 and the in-vehicle server device 10 may be conducted via the management server device as shown in the figure, or direct communication with the in-vehicle server device 10 may be conducted using a peer-to-peer communication method using a short-range wireless system, etc.

[0046] [Another configuration of the first embodiment] Next, another configuration of the car-sharing system of Embodiment 1 will be described with reference to the figures. Figure 6 is a block diagram showing an example of another configuration of the car-sharing system according to this embodiment. As shown in this figure, the car-sharing system according to another configuration of the first embodiment includes an in-vehicle server device 10 having a first encryption unit 20, a user device 11 having a determination unit 15 and a user key generation unit 16, and a management server device 19 having a service key generation unit 17, a conversion key generation unit 18, a registration unit 12 and a matching unit 14, and a second encryption unit 21.

[0047] The differences from the above [alternative configuration of the first embodiment] are that the encryption unit 13 is divided into a new first encryption unit 20 and a second encryption unit 21, and the registration unit 12 and verification unit 14 have been moved from the in-vehicle server device 10 to the management server device 19. Other configuration requirements, including their functions and configurations, have already been explained above, so they are omitted here.

[0048] The first encryption unit 20 encrypts the acquired biometric information features using the service's public key during authentication. The second encryption unit 21 obtains the features encrypted with the service's public key from the first encryption unit 20 of the in-vehicle server device 10 and uses a conversion key to convert the features encrypted with the service's public key into authentication query data encrypted with the user's public key.

[0049] By adopting this alternative configuration, it is possible to reduce the processing load on the in-vehicle server device and suppress the amount of storage used, thereby reducing the burden on in-vehicle equipment, which has limited resources such as power supply. Furthermore, processing that is computationally intensive, such as verification processing, can be performed on the management server device, which has relatively abundant processing resources, enabling faster and more stable processing.

[0050] Here, in the management server device 19, the service key generation unit 17 generates a pair of the service's public key and the service's private key. The conversion key generation unit 18 requires the service's private key to generate the conversion key. However, since the biometric information features encrypted with the service's public key are sent from the in-vehicle server device 10, there is a threat that if a malicious actor attacks the management server device, they could steal the service's private key, decrypt the biometric information features encrypted with the service's public key, and obtain the plaintext biometric information features. To mitigate this threat, it is desirable to take measures such as deleting the service's private key as soon as the conversion key generation process by the conversion key generation unit 18 is completed.

[0051] [System operation] Figure 7 is a flowchart showing the operation of the car-sharing system according to the first embodiment. Figure 7 shows a series of operations of the entire system until authentication is successful during system authentication. First, the biometric features of the service reservation holder are received (step S71). The received features are encrypted with the service's public key to generate a first ciphertext (step S72). Next, the first ciphertext is converted to a second ciphertext using one of the N (N: number of registered users) conversion keys that have been generated (step S73), and the encryption similarity is calculated using the registered ciphertext and the second ciphertext (step S74). This process (steps S73, S74) is repeated N times, which is the number of registered users (loop 1).

[0052] After the similarity calculation is complete, one of the N encrypted similarity values ​​is decrypted with the user's private key (step S75), and it is determined whether the similarity is within the acceptable range (step S76). This process (steps S75, S76) is repeated N times, equal to the number of similarity values ​​calculated (loop 2). Then, the user corresponding to the registered ciphertext data with the highest similarity among the similarities within the acceptable range is identified (step S77), and authentication is completed by performing processes such as matching it with the reservation data. After authentication is complete, in-vehicle equipment control, such as unlocking the keys, which is performed when authentication is OK, is executed (step S78).

[0053] [Hardware configuration] The car-sharing system of this embodiment is executable by an information processing device (computer) and consists of an in-vehicle server device 10, a user device 11, and a management server device 19, and has the configuration illustrated in Figure 8. The in-vehicle server device 10, the user device, and the management server device are interconnected by an internal bus 105 and include a CPU (Central Processing Unit) 101, memory 102, input / output interface 103, and a communication means such as a NIC (Network Interface Card) 104.

[0054] However, the configuration shown in Figure 8 is not intended to limit the hardware configuration of the car-sharing system. The in-vehicle server device 10, user device 11, and management server device 19 may include hardware not shown, and may not have an input / output interface 103 if necessary. Furthermore, the number of CPUs etc. included in these devices is not limited to the example in Figure 8; for example, multiple CPUs may be included in the in-vehicle server device 10, user device 11, and management server device 19.

[0055] Memory 102 consists of RAM (Random Access Memory), ROM (Read Only Memory), and auxiliary storage devices (such as hard disks).

[0056] The input / output interface 103 is a means that serves as an interface for a display device and an input device (not shown). The display device is, for example, a liquid crystal display. The input device is, for example, a camera or sensor that receives biological information, and a device that receives user input such as a keyboard or mouse.

[0057] The functions of the in-vehicle server device 10, user device 11, and management server device 19 are realized by a group of programs (processing modules) stored in memory 102, such as a registration program, encryption program, verification program, determination program, user key generation program, service key generation program, conversion key generation program, etc., and a group of data such as parameters used by each program. These processing modules are realized, for example, by the CPU 101 executing each program stored in memory 102. Furthermore, these programs can be downloaded via a network or updated using a storage medium that stores the programs. Moreover, the processing modules may be realized by semiconductor chips. In other words, there is a means to execute the functions performed by the processing modules using some hardware and / or software.

[0058] [Hardware operation] [Key generation process] In user device 11, the user key generation program is called from memory 102 and executed by CPU 101. This program generates a public key and private key pair for each user's user key and stores it in memory 102. In management server device 19, the service key generation program is called from memory 102 and executed by CPU 101. This program generates a public key and private key pair for the service key and stores it in memory 102. Next, in management server device 19, the conversion key generation program is called from memory 102 and executed by CPU 101. This program obtains the service's private key held in memory 102 and each user's public key stored in user device 11's memory 102 via NIC 104, and generates a conversion key using the service's private key and the user's public key. The generated conversion key is stored in the in-vehicle server device 10's memory 102 via NIC 104.

[0059] [Procedure during registration] The hardware operation during registration of biometric features in the car-sharing system of the first embodiment will now be described. In the in-vehicle server device 10, the registration program is called from memory 102 and enters execution mode on the CPU 101. The program controls an input / output interface 103 such as a camera to photograph the person registering for use, performs preprocessing, etc., and temporarily stores the biometric features in memory 102. Next, the program obtains the user's public key from the user device 11 via NIC 104. Using the obtained user's public key, the program encrypts the biometric features that were temporarily stored in memory 102 through calculations performed by the CPU 101 and stores them as registration ciphertext data in a predetermined storage area on memory 102.

[0060] [Authentication process] The hardware operation during authentication of the car-sharing system in the first embodiment will now be described. First, the encryption program stored in the memory 102 of the in-vehicle server device 10 is called by the CPU 101 and enters execution mode. This program acquires biometric characteristics of the user from the camera, which is the input / output interface 103, encrypts them through calculations performed by the CPU 101, and temporarily stores them in the memory 102 as encrypted authentication query data.

[0061] Next, in the in-vehicle server device 10, a matching program is called from memory 102 and executed by the CPU 101. This program calculates the encryption similarity (distance between features) Enc(D) by performing homomorphic arithmetic processing on the encrypted authentication query data of the user reservation stored in memory 102 and the registered ciphertext data also stored in a predetermined storage area of ​​memory 102, without going through decryption processing. The calculated encryption similarity Enc(D) is sent to the user device 11 via NIC 104. Next, in the user device 11, a judgment program is called from memory 102 and executed by the CPU 101. This program performs a comparison operation between the acquired D and d, which indicates a predetermined acceptance range, and determines whether D is less than or equal to d. If D is greater than or equal to d, it is rejected and an NG signal is sent to the in-vehicle server device via NIC 104. Conversely, if D is less than d, an OK signal is sent. The matching program selects the registered ciphertext corresponding to the OK signal and obtains the registered ciphertext with the smallest D value and the user ID associated with it.

[0062] After this, the control program of the in-vehicle server device 10 may be started to perform processes such as unlocking the vehicle doors.

[0063] [Explanation of effects] The car-sharing system of this embodiment provides a car-sharing system, sharing method, and program that contribute to preventing impersonation due to the leakage of biometric features stored in the in-vehicle device. Specifically, during authentication, the acquired biometric features are first encrypted with the service's public key, and then converted to each user's public key. This reduces the threat of the plaintext features remaining in memory during the encryption process being stolen by an attack.

[0064] [Summary of the process in the second embodiment] The car-sharing system of this embodiment has a reservation management unit and a pre-registration unit on the management server device, and it is possible to process the system by duplicating and distributing the registration ciphertext data from the pre-registration unit to the registration unit of the in-vehicle server device according to the reservation status. However, in the user device, the user's public key and private key are generated and stored within the user device. However, in this invention, the user device is intended to be a portable terminal such as a smartphone, so in addition to the threat of a malicious actor infiltrating the terminal via the network, there is also the threat of the terminal itself being stolen and the user's private key being illegally obtained. For this reason, a configuration in which all users' registration ciphertext data is stored in the in-vehicle server device is high-risk.

[0065] Therefore, in this embodiment, as described above, registered ciphertext data is stored in both the management server device and the in-vehicle server device, and the configuration allows for the appropriate copying of registered ciphertext data from the management server device to the in-vehicle server device according to the service reservation status, and for the deletion of registered ciphertext data that is not needed on the in-vehicle server device.

[0066] Figure 9 is a schematic diagram illustrating the processing overview of the car-sharing system according to the second embodiment. As shown in this figure, registration ciphertext data is registered (37, 38) in both the in-vehicle server device 10 and the management server device 19. A preliminary registration unit 38 and a registration unit 37 exist for each, and all or part of the registration ciphertext is copied from the preliminary registration unit 38 to the registration unit 37 depending on the service reservation status.

[0067] [Configuration of the second embodiment] Figure 10 is a block diagram showing the configuration of a car-sharing system according to the second embodiment. As shown in this figure, the car-sharing system of this embodiment includes an in-vehicle server device 10, a user device 11, and a management server device 19. The in-vehicle server device 10 has a registration unit 12, an encryption unit 13, a matching unit 14, and a control unit 23. The user device 11 has a determination unit 15 and a user key generation unit 16. The management server device 19 has a service key generation unit 17, a conversion key generation unit 18, a reservation management unit 24, and a preliminary registration unit 25. Note that the above configuration requirements have already been explained, so their description is omitted. The car-sharing system of this embodiment is characterized in that the management server device 19 has a reservation management unit 24 and a preliminary registration unit 25, and that the registration unit 12 obtains all or part of the registered ciphertext data from the preliminary registration unit 25 of the management server device 19 and registers it based on the service user reservation in the reservation management unit 24.

[0068] The reservation management unit 24 receives reservations from service users in the management server device 19 and manages the service users. In this embodiment, "management" refers to processes such as extracting the user IDs of users who have made reservations for the day from among the registered users and selecting the registration ciphertext associated with the user IDs registered in the pre-registration unit 25. This process may be performed at predetermined intervals, or each time the data in the pre-registration unit 25 described later is updated, or each time a new reservation is set in the reservation management unit 24.

[0069] The preliminary registration unit 25 registers encrypted registration ciphertext data containing the biometric information of prospective service users in the management server device 19. In the car-sharing system of this embodiment, the preliminary registration unit 25 becomes the master of the registration ciphertext, and the registration unit 12 of the in-vehicle user device becomes the slave. Therefore, the registration ciphertext based on the biometric features acquired at the time of user registration is registered in the preliminary registration unit 25. On the other hand, the registration unit 12 of the in-vehicle server device 10 acquires all or part of the registration ciphertext data from the preliminary registration unit 25 of the management server device 19 and registers it based on the service user reservation in the reservation management unit 24.

[0070] [System operation] Figure 11 is a flowchart showing part of the operation of the car-sharing system according to the second embodiment. This figure mainly shows the process when a user is registered. First, the biometric characteristics of the prospective service user are received (step S101). Next, a registration ciphertext is generated using the public key of each prospective user to be registered (step S102). Next, the registration ciphertext is stored in the spare registration unit of the management server device (step S103). Next, it is determined whether or not the update timing has arrived up to this point (step S104). If it has not arrived (step S104; N), the process returns to receiving the biometric characteristics of the prospective service user (step S101). If it has arrived (step S104; Y), the user ID of the user who has made a reservation is selected from the registered user IDs, etc. Next, the registration ciphertext of the selected user is duplicated and stored in the registration unit for registration.

[0071] [Explanation of effects] In the car-sharing system of this embodiment, it is possible to control the amount of registered ciphertext to be matched according to the reservation status. This makes it possible to reduce the time required for encryption and re-encryption using the conversion key, and enables sufficient performance even in an in-vehicle server device with limited processing resources.

[0072] Some or all of the embodiments described above can also be described as follows. However, these following appendices are merely illustrative examples of the present invention, and the present invention is not limited to these cases. [Note 1] This is as described in the first perspective regarding the car-sharing system mentioned above. [Note 2] Preferably a car-sharing system as described in Appendix 1, which includes an in-vehicle server device, the user device further comprising a user key generation unit that generates a pair of the user's public key and the user's private key, a service key generation unit that generates a pair of the service's public key and the service's private key, and a conversion key generation unit that uses the user's public key and the service's private key to generate a second encrypted message encrypted with the user's public key from a first encrypted message encrypted with the service's public key, the encryption unit encrypts the biometric information of the service user reservation holder with the service's public key, and further re-encrypts the encrypted biometric information using the conversion key to obtain encrypted authentication query data. [Note 3] Preferably the car-sharing system as described in Appendix 2, further comprising an in-vehicle server device having a control unit that controls the vehicle on which the user device is installed based on the determination result of the determination unit of the user device. [Note 4] Preferably, the car-sharing system as described in Appendix 2 or 3, wherein the matching unit of the in-vehicle server device calculates the (encrypted) similarity between the registered ciphertext and the encrypted authentication query data while both are encrypted, and the determination unit decrypts the encrypted similarity using the user's secret key and determines whether or not the authentication is within the acceptable range based on the decrypted similarity. [Note 5] At least the encrypted authentication query data is fully homomorphic, with homomorphic operations defined for multiple multiplications and additions, and the matching unit calculates the distance between the features related to the registered ciphertext and the authentication query data using homomorphic operations to obtain the similarity score, preferably the car-sharing system as described in Appendix 4. [Note 6] The management server device further comprises a reservation management unit that accepts reservations from service users and manages service users, and a preliminary registration unit that registers registration ciphertext data that encrypts the biometric information of prospective service users, and the registration unit of the in-vehicle server device obtains all or part of the registration ciphertext data from the preliminary registration unit of the management server device and registers it based on the service users in the reservation management unit, preferably a car-sharing system according to any one of appendices 2 to 5. [Note 7] A car-sharing system, preferably one of the specifications 1 to 6, in which a user device and an in-vehicle server device communicate peer-to-peer. [Note 8] The sharing method for the second perspective described above is as follows. [Note 9] The authentication server device related to the third perspective described above is as follows. [Note 10] The program related to the fourth perspective described above is as follows.

[0073] Furthermore, each disclosure of the above-mentioned patent documents, etc., cited herein shall be incorporated by reference. Within the framework of the full disclosure of the present invention (including the claims), further modifications and adjustments to the embodiments are possible based on the fundamental technical concept. Also, within the framework of the full disclosure of the present invention, various combinations or selections (including partial deletions) of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible. In other words, the present invention naturally includes various modifications and changes that a person skilled in the art could make in accordance with the full disclosure, including the claims, and the technical concept. In particular, with respect to the numerical ranges described herein, any numerical value or sub-range included within that range should be interpreted as being specifically described unless otherwise stated. [Explanation of symbols]

[0074] 10: In-vehicle server device 11: User device 12: Registration Department 13: Encryption section 14: Verification section 15: Judgment section 16: User Key Generation Unit 17: Service Key Generation Unit 18: Conversion Key Generation Unit 19: Management Server Device 20:First encryption part 21:Second encryption part 23: Control Unit 24: Reservation Management Department 25: Preliminary Registration Section 31: Public Key 32: Private key 33: Conversion Key 34: Encrypted biometric features 35: Encryption Authentication Query Data 36: Registered Cipher Text 37: Registration Department 38: Preliminary Registration Section 101: CPU 102: Memory 103: Input / Output Interface 104: NIC 105: Internal bus

Claims

1. A registration unit that registers encrypted registration ciphertext data containing the biometric information of prospective service users, An encryption unit is provided to authenticate the service user by encrypting the biometric information of the service user and converting it into encrypted authentication query data. A matching unit that compares the registered ciphertext data and the encrypted authentication query data while both are encrypted, An in-vehicle server device having, A determination unit determines whether or not the authentication is within the acceptable range based on the verification result of the verification unit, A user key generation unit that generates a pair of the user's public key and the user's private key, A user device having, A service key generation unit that generates a pair of the public key of the service and the private key of the service, A conversion key generation unit generates a conversion key that generates a second ciphertext encrypted with the user's public key from a first ciphertext encrypted with the service's public key, using the user's public key and the service's private key. A management server device having, Includes, The car-sharing system comprises an encryption unit that encrypts the biometric information of the service user with the public key of the service, and further re-encrypts the encrypted biometric information using the conversion key to obtain the encrypted authentication query data.

2. The in-vehicle server device includes a control unit that controls the vehicle on which it is mounted based on the determination result from the determination unit of the user device, A car-sharing system according to claim 1, further comprising the above.

3. The matching unit of the in-vehicle server device calculates the encryption similarity between the registered ciphertext data and the encrypted authentication query data while both are encrypted. The determination unit decrypts the encrypted similarity using the user's private key and determines whether or not the authentication is within the acceptable range based on the decrypted similarity. The car-sharing system according to claim 1.

4. At least the encryption authentication query data is a homomorphic encryption in which homomorphic operations are defined with respect to multiple multiplications and additions, and the matching unit calculates the distance between feature quantities relating to the registered ciphertext data and the encryption authentication query data by the homomorphic operations and uses this as the encryption similarity. The car-sharing system according to claim 3.

5. The aforementioned management server device is A reservation management department that accepts reservations from the aforementioned service users and manages the aforementioned service users' reservations, A preliminary registration unit that registers the aforementioned registered ciphertext data, which is encrypted biometric information of a prospective service user, It further possesses, The registration unit of the in-vehicle server device acquires all or part of the registration ciphertext data from the preliminary registration unit of the management server device and registers it based on the service user reservation in the reservation management unit. A car-sharing system according to any one of claims 1 to 4.

6. A car-sharing system according to any one of claims 1 to 4, wherein the user device and the in-vehicle server device communicate with each other on a peer-to-peer basis.

7. A sharing method using an in-vehicle server device, a management server device, and a user device, The steps include: the user device generating a pair of the user's public key and the user's private key; The management server device generates a pair of the public key of the service and the private key of the service, The management server device generates a conversion key using the user's public key and the service's private key to generate a second ciphertext encrypted with the user's public key from a first ciphertext encrypted with the service's public key, The in-vehicle server device registers encrypted registration ciphertext data containing the biometric information of a prospective service user, The in-vehicle server device encrypts the biometric information of the service user with the public key of the service, and further re-encrypts the encrypted biometric information using the conversion key to obtain encrypted authentication query data. The in-vehicle server device performs a step of comparing the registered ciphertext data and the encrypted authentication query data while both are encrypted. The steps include determining whether the user device is within the scope of authentication acceptance based on the results of the verification, Sharing methods including.

8. This is a program to be executed by the in-vehicle server device, the management server device, and the user device. The user device is instructed to perform the process of generating a pair of the user's public key and the user's private key. The management server device is instructed to perform the process of generating a pair of the service's public key and the service's private key. The management server device is instructed to perform a process using the user's public key and the service's private key to generate a conversion key that generates a second encrypted message, encrypted with the user's public key, from a first encrypted message encrypted with the service's public key. The in-vehicle server device is instructed to perform the process of registering encrypted registration data containing the biometric information of the prospective service user. The in-vehicle server device is instructed to encrypt the biometric information of the service user with the public key of the service, and then re-encrypt the encrypted biometric information using the conversion key to create encrypted authentication query data. The in-vehicle server device is instructed to perform a process of comparing the registered ciphertext data and the encrypted authentication query data while both are encrypted. A program that causes the user device to perform a process to determine whether or not the result of the verification falls within the scope of acceptable authentication.

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