JP2017069755A - Computer program and relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a security level of communication between two devices at a necessary level in the case of relaying communication between the two devices.SOLUTION: A relay server 200 establishes first encryption communication with a service providing server 300 by using an encryption system selected from one or more first encryption systems which can be used by the service providing server 300, and receives a system list indicating a plurality of available encryption systems from the device 100, and selects a second encryption system from among the plurality of encryption systems indicated by the system list after the first encryption communication is established. The selected second encryption system is either the same encryption system as the first encryption system or an encryption system having a security level equal to or higher than the first encryption system. The relay server 200 establishes second encryption communication with the device 100 by using the second encryption system, and relays communication between the service providing server and the device by using the first encryption communication and the second encryption communication.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a technology for relaying communication between a communication device and a service providing device that provides a specific service to the communication device.

  Patent Document 1 discloses a third communication device having a function of relaying communication between the first communication device and the second communication device. The third communication device encrypts a first encryption key used for communication between the first communication device and the third communication device, and a second encryption key used for communication between the second communication device and the third communication device. Check the type and key length. When the encryption type and the key length match between the first encryption key and the second encryption key, the third communication device transmits the first encryption key to the second communication device. The third communication device uses the first encryption key for both communication between the first communication device and the third communication device and communication between the second communication device and the third communication device. Do it. As a result, the third communication apparatus can simply relay the encrypted data without performing decryption or encryption, and therefore can efficiently perform the relay.

JP 2001-237818 A

  However, in the above technique, when the encryption type and the key length match, only the encryption key is shared, so two devices to be relayed (for example, the first communication device and the first communication device) There is a possibility that the security level of communication with the (2 communication devices) cannot be maintained at a necessary level.

  The present specification discloses a technique capable of maintaining a communication security level between two devices at a necessary level when relaying communication between the two devices.

  The technology disclosed in this specification can be implemented as the following application examples.

Application Example 1 A computer program for a relay device using an encryption method selected from one or more first encryption methods that can be used by a service providing device that provides a specific service. A first establishment function for establishing first encrypted communication with a service providing device, and a first reception function for receiving a method list indicating a plurality of encryption methods usable by the communication device from the communication device And a selection function for selecting a second encryption method from a plurality of encryption methods shown in the method list based on the first encryption method after the first encrypted communication is established. The selected second encryption method is either the same encryption method as the first encryption method or an encryption method having a security level higher than that of the first encryption method. The selection function and the previous Using a second establishment function for establishing a second encrypted communication with the communication device using a second encryption method, using the first encrypted communication and the second encrypted communication, A computer program that causes a computer to realize a relay function for relaying communication between a service providing device and the communication device.

  According to the above configuration, the second encryption method of the second encrypted communication to be established between the relay device and the communication device based on one or more first encryption methods that can be used by the service providing device. Selected. Then, either the same encryption method as the first encryption method or an encryption method having a higher security level than the first encryption method is selected as the second encryption method. Therefore, it is possible to suppress a decrease in the security level of the second encryption method compared to the first encryption method. Therefore, when the relay device relays communication between the communication device and the service providing device, a security level of communication between the communication device and the service providing device is required (for example, the service providing device requests). Level).

  The technology disclosed in this specification can be realized in various forms, and is connected to, for example, a communication device and a service providing device that provides a specific service to the communication device. A relay device, a communication device, and a communication relay method between the communication device and a service providing device that provides a specific service to the communication device, a recording medium in which the computer program is recorded (for example, a non-temporary recording medium) ), And the like.

1 is a block diagram showing a configuration of a system 1000. FIG. 2 is a conceptual diagram of information included in devices in the system 1000. FIG. FIG. 11 is a sequence diagram illustrating an example of communication in the system 1000. FIG. 11 is a sequence diagram illustrating an example of communication in the system 1000. It is a flowchart of the re-establishment judgment process of 1st Example. FIG. 11 is a sequence diagram illustrating an example of communication in the system 1000. FIG. 11 is a sequence diagram illustrating an example of communication in the system 1000. It is a figure which shows an example of the reference information RI. It is a flowchart of the re-establishment judgment process of 2nd Example.

A. First embodiment:
A-1: Configuration of System 1000 Next, an embodiment will be described based on examples. FIG. 1 is a block diagram illustrating a configuration of a system 1000 according to the present embodiment. FIG. 2 is a conceptual diagram of information held by devices in the system 1000.

  The system 1000 includes a device 100 as a communication apparatus, a relay server 200, and a service providing server 300. The device 100 is connected to a LAN (Local Area Network) 70. The LAN 70 is connected to the Internet 80. The relay server 200 and the service providing server 300 are connected to the Internet 80. As a result, the device 100 and the relay server 200, and the relay server 200 and the service providing server 300 can communicate with each other via the LAN 70 and the Internet 80.

  The device 100 is a so-called multifunction device that executes image processing such as image printing and image scanning. The device 100 is not limited to a multifunction peripheral, and may be another image processing device such as a scanner, a printer, or a digital camera, or may be a general-purpose device such as a portable terminal device or a personal computer. The device 100 includes a CPU 110, a nonvolatile storage device 120 such as a hard disk drive or an EEPROM, a volatile storage device 130 such as a RAM, and a printer unit that prints an image using a predetermined method (for example, a laser method or an inkjet method). 140, a scanner unit 150 that acquires scan data by optically reading an object (for example, a paper document), an operation unit 160 such as a touch panel or a button, and a display unit such as a liquid crystal panel superimposed on the touch panel. 170 and a network interface (IF) 180. The network IF 180 is an interface compliant with, for example, the Ethernet (registered trademark) standard, and is used to connect to the LAN 70.

  The nonvolatile storage device 120 stores a computer program PG1, server information SI, and an encryption method list CL1. The volatile storage device 130 is provided with a buffer area 131 for temporarily storing various intermediate data generated when the CPU 110 performs processing.

  The computer program PG1 is provided in a form stored in advance in the nonvolatile storage device 120 when the device 100 is shipped. The computer program PG1 may be provided in a form downloaded from a server connected to the device 100 via the Internet 80, or may be provided in a form stored in a CD-ROM or DVD-ROM.

  The CPU 110 functions as a controller of the device 100 by executing the computer program PG1. For example, the CPU 110 controls the printer unit 140 and the scanner unit 150 to execute printing and scanning. Further, the CPU 110 can realize a server communication function for communicating with the service providing server 300 via the relay server 200. Although details will be described later, the server communication function of the present embodiment is executed to transmit various status information of the device 100 to the service providing server 300.

  The server information SI is server information to be communicated in the server communication function. The server information SI is information indicating the relay server 200 with which the device 100 should directly communicate, specifically, the URL of the relay server 200 and an identifier indicating the service providing server 300 used by the device 100 (hereinafter, used). Also called a server ID).

  The encryption method list CL1 is a list indicating a plurality of encryption methods that the device 100 can use. The encryption method is a method of encrypted communication between the device 100 and an external device (for example, the relay server 200) connected to the device 100 via a network. The encryption method is defined by an encryption suite that shows a plurality of algorithms used in encrypted communication side by side.

  FIG. 2A shows an example of the encryption method list CL1. The encryption method list CL1 includes a plurality of encryption suites each indicating an encryption method. The multiple item algorithm included in one encryption method includes a key exchange algorithm, an authentication algorithm, an encryption algorithm, and a hash algorithm.

  The key exchange algorithm is an algorithm for exchanging an encryption key (shared key) used for encryption of communication data between two apparatuses that perform communication. For example, “RSA”, “DHE (abbreviation of Diffie-Hellman key Exchange)”, and “ECDHE (abbreviation of Elliptic Curve Diffie-Hellman key Exchange)” are used as the key exchange algorithm.

  The RSA key exchange algorithm includes a process in which the first device transmits encrypted data obtained by encrypting the shared key using the public key of the second device to the second device. The second device acquires the shared key by decrypting the encrypted data using the self-confidential private key. Since the third party does not have the secret key, the eavesdropping encrypted communication cannot be decrypted. However, if a third party can obtain a secret key in the future, the third party can decrypt and view the encrypted communication that has been wiretapped so far. Therefore, the RSA key exchange algorithm cannot achieve so-called PFS (abbreviation of Perfect Forward Secrecy).

  On the other hand, in the DHE key exchange algorithm and the ECDHE key exchange algorithm, a shared key is exchanged using random parameters generated by the first device and the second device for each session. Even if these parameters are leaked, they do not affect the security of communication in another session. Therefore, the DHE key exchange algorithm and the ECDHE key exchange algorithm can achieve so-called PFS.

  From this point of view, it can be said that the DHE key exchange algorithm and the ECDHE key exchange algorithm have a higher security level than the RSA key exchange algorithm.

  The authentication algorithm is an algorithm for authenticating at least one of the two devices that perform communication. For example, “RSA” or “DSA (abbreviation of Digital Signature Algorithm)” is used as the authentication algorithm.

  The encryption algorithm is an algorithm for encrypting communication data using an exchanged encryption key (shared key). For example, “DES (abbreviation of Data Encryption Standard)”, “3DES (abbreviation of Triple Data Encryption Standard)”, and “AES (abbreviation of Advanced Encryption Standard)” are used as the encryption algorithm. In addition, a number (for example, 128, 256) indicating the key length of the encryption key is added to the end of each alphabet indicating the encryption algorithm, and expressed as, for example, DES128, DES256. Between encryption algorithms of the same type, the longer the key length, the higher the security level.

  The hash algorithm is an algorithm for generating a digest of data. The hash algorithm is used in at least one of the other algorithms. The hash algorithm is used, for example, for generating signature data or verifying an electronic certificate in an authentication algorithm. As the hash algorithm, for example, “SHA (abbreviation of Secure Hash Algorithm) 1”, “SHA256”, “SHA512”, and the like are used. The security level is higher in the order of “SHA512”> “SHA256”> “SHA1”.

  Here, in this embodiment, as shown in FIG. 2, four types of encryption methods A to D are used. FIG. 2 shows encryption suites indicating the encryption methods A to D. As can be seen from these encryption suites, the key exchange-authentication-encryption-hash algorithm combination of encryption method A is “RSA”-“RSA”-“AES128”-“SHA256”. Then, the combination of algorithms of the encryption method B is “RSA” − “RSA” − “AES256” − “SHA256”. The combination of encryption scheme C algorithms is “DHE”-“RSA”-“AES128”-“SHA1”. The combination of algorithms is “DHE”-“RSA”-“AES256”-“SHA1”.

  As shown in FIG. 2A, the encryption method list CL1 includes an encryption suite indicating the encryption method A and an encryption suite indicating the encryption method C. That is, the device 100 can use two encryption methods A and C.

  The relay server 200 (FIG. 1) is a server provided by the device 100 vendor. As will be described in detail later, the relay server 200 relays communication between a plurality of devices including the device 100 and a plurality of service providing servers including the service providing server 300.

  The relay server 200 includes a CPU 210, a nonvolatile storage device 220 such as a hard disk drive, a volatile storage device 230 such as a RAM, and a network IF 280 for connecting to the Internet 80.

  The nonvolatile storage device 220 stores a computer program PG2, an encryption method list CL2, and registration information CI. The reference information RI indicated by the wavy line is information held by the relay server 200 in the second embodiment, and will be described in the second embodiment. The volatile storage device 230 is provided with a buffer area 231 for temporarily storing various intermediate data generated when the CPU 210 performs processing.

  The computer program PG2 may be provided in a form uploaded from a vendor computer connected via the Internet 80, or may be provided in a form stored in a CD-ROM, DVD-ROM, or the like. The CPU 210 implements a function as a controller of the relay server 200 by executing the computer program PG2. Details of these functions will be described later.

  The encryption method list CL2 is a list indicating a plurality of encryption methods that can be used by the relay server 200. As shown in FIG. 2B, the encryption method list CL2 includes four encryption suites indicating the four encryption methods A to D. That is, the relay server 200 can use four encryption methods A to D. The relay server 200 communicates not only with the device 100 but also with a plurality of other devices (not shown), for example, multifunction devices, scanners, and printers sold by vendors that provide the relay server 200. The relay server 200 communicates not only with the service providing server 300 but also with a plurality of other service providing servers (not shown). Therefore, it is preferable that the relay server 200 can use many encryption methods that can be used by these devices and the service providing server.

  As shown in FIG. 2C, the registration information CI includes a device table DT and a server table ST.

  The device table DT is a table in which information on a device (for example, the device 100) that is establishing encrypted communication with the relay server 200 is registered. One entry E1 registered in the device table DT includes a device ID (for example, D01), a used encryption method (for example, encryption method A), and a usage server ID (for example, SV1). The device ID is an identifier indicating a device that is establishing encrypted communication. The used encryption method is an encryption method used in the encrypted communication being established. The server ID is an identifier indicating a service providing server used by a device that is establishing encrypted communication.

  The server table ST is a table in which information of a service providing server (for example, the service providing server 300) that has established encrypted communication with the relay server 200 is registered. One entry E2 registered in the server table ST includes a server ID (for example, SV1) and an encryption method list (for example, list CL2). The server ID is an identifier indicating a service providing server that has established encrypted communication. The encryption method list is an encryption method list received from a service providing server that has established encrypted communication.

  The service providing server is a server that provides a specific service to a client (for example, the device 100). For example, the service providing server 300 provides a service for managing a plurality of devices to be managed including the device 100 to the administrator of the plurality of devices. The service providing server 300 may be provided by a vendor of the device 100, or may be provided by an operator different from the vendor of the device 100. For example, the service providing server 300 receives a plurality of pieces of information indicating the status of a plurality of devices to be managed, for example, the number of prints, the status of consumables such as color materials such as toner and ink, and the occurrence status of a failure or error. Collect from devices. The administrator of the plurality of devices provides information indicating the status of the plurality of devices from the service providing server 300 by accessing the service providing server 300 using a terminal device (for example, a personal computer) (not shown). Can receive.

  The service providing server 300 includes a CPU 310, a nonvolatile storage device 320 such as a hard disk drive, a volatile storage device 330 such as a RAM, and a network IF 380 for connecting to the Internet 80.

  The nonvolatile storage device 320 stores a computer program PG3 and an encryption method list CL3. The volatile storage device 330 is provided with a buffer area 331 for temporarily storing various intermediate data generated when the CPU 310 performs processing.

  The computer program PG3 may be provided in a form uploaded from a computer of an operator of the service providing server 300 connected via the Internet 80, or provided in a form stored in a CD-ROM or DVD-ROM. May be. The CPU 310 implements a function as a controller of the service providing server 300 by executing the computer program PG3. Details of these functions will be described later.

  The encryption method list CL3 is a list indicating one or more encryption methods that can be used by the service providing server 300. As shown in FIG. 2D, the encryption method list CL3 includes two encryption suites indicating the two encryption methods C and D. That is, the service providing server 300 can use two encryption methods C and D.

A-2: Operation of System 1000 In this embodiment, the user of the service providing server 300 is an administrator who manages a plurality of devices including the device 100. This administrator accesses the service providing server 300 using a terminal device at a location (for example, an administrator's office) different from the installation location of a plurality of devices to be managed. As a result, the status of a plurality of devices to be managed is acquired via the service providing server 300. The administrator can charge the user of the device based on these statuses (for example, the number of printed sheets and the amount of color material consumed).

  In the present embodiment, users of a plurality of devices including the device 100 are different from the above-mentioned administrator. As an example, the user receives and leases these devices from the administrator. In the device 100, the server information SI described above is stored in advance by an administrator, and the device 100 is set to transmit a status to the service providing server 300 via the relay server 200.

A-2-1. Communication Protocol In this embodiment, a communication protocol between a plurality of devices including the device 100 and the relay server 200 will be described. Communication between each device and the relay server 200 is performed by using each device as a client and the relay server 200 as a server according to a program of an application layer of each device and the relay server 200 (hereinafter simply referred to as an application). Done. Each device and the application of the relay server 200 perform communication according to XMPP (abbreviation of Extensible Messaging and Presence Protocol) which is an application layer protocol. Communication in the transport layer below the application is performed according to TCP (abbreviation of Transmission Control Protocol). An encrypted secure communication path (hereinafter referred to as “Secure Sockets Layer / Transport Layer Security”) that is lower than the XMPP of the application layer and higher than the TCP of the transport layer by communication according to SSL / TLS (Secure Sockets Layer / Transport Layer Security). Simply referred to as encrypted communication). That is, between each device and the relay server 200, both applications transmit and receive application data using encrypted communication established according to SSL / TLS.

  In this embodiment, a communication protocol between the relay server 200 and a service providing server including the service providing server 300 will be described. Communication between the relay server 200 and the service providing server is performed using the service providing server as a client and the relay server 200 as a server according to the respective applications of the relay server 200 and the service providing server. The relay server 200 and the application of the service providing server perform communication according to HTTP (abbreviation of Hypertext Transfer Protocol) which is an application layer protocol. Communication in the transport layer below the application is performed according to TCP. Then, encrypted communication according to SSL / TLS (abbreviation of Transport Layer Security / Secure Sockets Layer) is established in a layer between HTTP of the application layer and TCP of the transport layer. That is, in the communication between the relay server 200 and the service providing server, both applications use the encrypted communication established according to SSL / TLS as in the case between each device and the relay server 200. Send and receive application data.

A-2-2: Communication of System 1000 The operation of the system 1000 will be described using communication between the device 100, the relay server 200, and the service providing server 300 as a specific example. 3 and 4 are sequence diagrams illustrating an example of communication in the system 1000. FIG. This sequence diagram is an example in the case where the device 100 accesses the relay server 200 before the encryption method list CL3 of the service providing server 300 is registered in the relay server 200.

  The device 100 accesses the relay server 200 when power is turned on, and establishes XMPP communication with the relay server 200. As a result, a state is established in which both the device 100 and the relay server 200 can independently communicate at an arbitrary timing. XMPP communication between the device 100 and the relay server 200 can be re-established as will be described later, but is always maintained while the device 100 is powered on.

  Specifically, first, in S <b> 10, the CPU 110 of the device 100 transmits a communication start request to the relay server 200. The transmission destination relay server 200 is specified based on the server information SI described above. The communication start request includes the encryption method list CL1 of FIG. When the relay server 200 receives the encryption method list CL1, in S12, the CPU 210 of the relay server 200 includes a plurality of encryption methods A and C (FIG. 2A) indicated in the encryption method list CL1. From this, one encryption method to be used (hereinafter referred to as a used encryption method) is selected. Specifically, the encryption methods A and C (FIG. 2A) shown in the encryption method list CL1 and the relay server 200 itself can be used (that is, FIG. 2). One of the encryption methods A to D shown in the encryption method list CL2 in (B) is selected as the used encryption method. The selection of the encryption method in S12 is performed by an arbitrary method, but in this embodiment, the encryption method A shown at the top in the encryption method list CL1 is selected.

  In S <b> 14, the CPU 210 transmits a notification of the used encryption method, in this embodiment, the encryption method A, to the device 100. Note that the communication in S10 and S14 is communication between SSL / TLS layers.

  When the device 100 receives the notification of the encryption method used, communication establishment processing is performed between the device 100 and the relay server 200 in S16. That is, communication for establishing encrypted communication using the encryption method A, which is the encryption method used, between the device 100 and the relay server 200 is executed according to SSL / TLS. In this process, for example, according to the encryption method A, the process of authenticating the relay server 200 includes a process of exchanging a shared key. Further, communication for establishing XMPP communication is executed in accordance with XMPP on the established encrypted communication.

  In S <b> 18, the CPU 110 transmits the device ID and the usage server ID to the relay server 200 using the established encrypted communication and the XMPP communication established on the encrypted communication. That is, transmission / reception of the device ID and the usage server ID is communication between the application of the device 100 and the relay server 200. The device ID is an identifier indicating the device 100 itself. The use server ID is information included in the server information SI described above, and is an identifier indicating the service providing server 300. As the usage server ID, for example, the global IP address of the device 100 is used.

  When the relay server 200 receives the device ID and the usage server ID, in S20, the CPU 210 registers the device 100 with which communication with the relay server 200 has been established. Specifically, the CPU 210 associates the received device ID, the use server ID, and the encryption method used for communication established with the device, and described above with reference to FIG. ) In the device table DT. For example, the device ID “D01” indicating the device 100, the encryption method A used in the communication established between the device 100 and the relay server 200, and the usage server ID “SV1” indicating the service providing server 300 are used. And an entry E1 (FIG. 2C) is recorded. The entry E1 is updated when communication with the device 100 is re-established as will be described later. Further, when the communication with the device 100 is disconnected without being re-established, specifically, when the power of the device 100 is turned off, it is deleted.

  In S21, the CPU 210 executes a re-establishment determination process for determining whether to re-establish communication established with the device 100 by changing the encryption method used.

  FIG. 5 is a flowchart of the re-establishment determination process according to the first embodiment. In S100, the CPU 210 determines whether the established communication partner is a device (for example, the device 100) or a service providing server (for example, the service providing server 300). The established communication partner is an apparatus registered in the device table DT or the server table ST immediately before. For example, in the re-establishment determination process in S21 of FIG. 3, since the apparatus registered in the immediately preceding S20 is the device 100, it is determined that the established communication partner is a device.

  When the established communication partner is a device, the processes of S105 to S125 are executed. When the established communication partner is a service providing server, the processes of S130 to S155 are executed. Here, the processing of S105 to S125 will be described, and the processing of S130 to S155 will be described later.

  In S105, the CPU 210 identifies a service providing server associated with a device (hereinafter also referred to as a target device) that is an established communication partner, that is, a utilization server used by the target device. Specifically, the CPU 210 refers to the device table DT of FIG. 2C and acquires the use server ID associated with the device ID of the target device. As a result, the usage server identified by the usage server ID is specified. In the re-establishment determination process in S21 of FIG. 3, the service providing server 300 is specified as the usage server associated with the device 100.

  In S110, the CPU 210 determines whether or not the encryption method list of the specified usage server has been registered in the server table ST.

  If the encryption method list of the use server is registered in the server table ST (S110: YES), in S115, the CPU 210 determines that the encryption method currently established with the target device is use. It is determined whether it is included in the server encryption method list.

  When the encryption method currently established with the target device is not included in the encryption method list of the use server (S115: NO), the CPU 210 re-establishes with the target device in S120. It is determined that the process is to be performed, and the re-establishment determination process is terminated.

  When the encryption method list of the use server is not registered (S110: NO), and when the encryption method currently established with the target device is included in the encryption method list of the use server In (S115: YES), in S125, the CPU 210 determines not to perform the re-establishment process with the target device, and ends the re-establishment process.

  Returning to FIG. 3, the description will be continued. At the time of the re-establishment determination process in S21, communication between the service providing server 300, which is a use server of the device 100, and the relay server 200 has not been established yet. Therefore, the encryption method list of the service providing server 300 is not registered in the server table ST. For this reason, in S110 of FIG. 5, it is determined that the encryption method list of the usage server is not registered. Therefore, in the re-establishment determination process of S21, it is determined that the re-establishment process is not performed with the device 100 that is the target device.

  For this reason, after S21, the CPU 210 does not perform re-establishment processing. Therefore, the encrypted communication established in S16 and the XMPP communication established on the encrypted communication between the device 100 and the relay server 200 are maintained in the established state.

  The service providing server 300 accesses the relay server 200 periodically, for example, once a day, in order to obtain the status of a plurality of devices to be managed including the device 100. Specifically, in S22, CPU 310 of service providing server 300 transmits a communication start request to relay server 200. The communication start request includes the encryption method list CL3 of FIG. When the relay server 200 receives the encryption method list CL3, in S24, the CPU 210 selects one of the plurality of encryption methods C and D (FIG. 2D) shown in the encryption method list CL3. Select the encryption method used. The selection of the encryption method in S24 is performed by an arbitrary method, but in this embodiment, the encryption method C shown at the top in the encryption method list CL3 is selected.

  In S <b> 26, the CPU 210 transmits a notification of the encryption method used, in this embodiment, the encryption method C, to the service providing server 300. Note that the communication in S22 and S26 is communication between SSL / TLS layers.

  When the service providing server 300 receives the notification of the encryption method in use, communication establishment processing is performed between the service providing server 300 and the relay server 200 in S28. That is, communication for establishing encrypted communication using the encryption method C, which is the encryption method used, between the service providing server 300 and the relay server 200 is executed according to SSL / TLS. As a result, an HTTP request and a response can be transmitted and received between the service providing server 300 and the relay server 200 using the encrypted communication.

  In S30, the CPU 310 of the service providing server 300 transmits a status request for requesting the status of the device to be managed to the relay server 200 using the encrypted communication established in S28. The status request includes a server ID that is an identifier indicating the service providing server 300 and designation information for designating a device to be managed. The status request is transmitted as an HTTP request.

  The designation information is information different from each device ID for designating a specific device, and is information for designating all devices that request transmission of status requests. That is, the relay server 200 transmits a status request to all the devices that transmit the use server ID indicating the service providing server 300 by receiving the designation information.

  When the relay server 200 receives the status request, in S32, the CPU 210 registers the encryption method list CL3 of the service providing server 300 with which communication with the relay server 200 has been established. Specifically, the CPU 210 records the server ID included in the status request and the encryption method list CL3 received in S22 in association with each other in the server table ST. For example, as illustrated in FIG. 2C, an entry E2 including a server ID “SV1” indicating the service providing server 300 and an encryption method list CL3 of the service providing server 300 is recorded. The entry E2 is not deleted even after the communication with the service providing server 300 is disconnected. This entry E2 is updated when the content of the encryption method list CL3 is updated when communication with the service providing server 300 is established next time.

  In S34, the CPU 210 executes the re-establishment determination process of FIG. In the re-establishment determination process in S34, the established communication partner, that is, the device registered in the immediately preceding S32 is the service providing server 300. Accordingly, in S100 of FIG. 5, it is determined that the established communication partner is a service providing server. As a result, the CPU 210 executes the processes of S130 to S155 in FIG. Hereinafter, a service providing server that is an established communication partner is also referred to as a target server.

  In S <b> 130, the CPU 210 refers to the device table DT of FIG. 2C, and selects a device with which the target server is associated as a use server among devices that are currently establishing communication with the relay server 200. Identify. The target server is the service providing server 300 in the re-establishment determination process in S34 of FIG. Therefore, the device 100 with the device ID “D01” is specified based on the entry E1 including the server ID “SV1” of the service providing server 300 among the plurality of entries in the device table DT. In S130, a plurality of devices may be specified or a device may not be specified.

  In S132, the CPU 210 determines whether or not a device is specified in S130. When the device is not specified (S132: NO), the CPU 210 ends the re-establishment determination process. When one or more devices are identified (S132: YES), in S135, the CPU 210 selects one device to be determined from the identified devices.

  In S140, the CPU 210 determines whether or not the encryption method currently established with the determination target device is included in the encryption method list of the target server. In the re-establishment determination process of S34 in FIG. 3, the target server is the service providing server 300. The device to be determined is the device 100, and the encryption method currently established with the device 100 is the encryption method A as described above. The encryption method A is not included in the encryption method list CL3 (FIG. 2D) of the service providing server 300 registered in the server table ST. Therefore, in this case, it is determined that the encryption method currently established with the device to be determined is not included in the encryption method list of the target server. Assume that the encryption method currently established with the device 100 is the encryption method C as described above. The encryption method C is included in the encryption method list CL3 (FIG. 2D) of the service providing server 300 registered in the server table ST. Therefore, in this case, it is determined that the encryption method currently established with the determination target device is included in the encryption method list of the target server.

  If the encryption method currently established with the determination target device is not included in the encryption method list of the target server (S140: NO), in S145, the CPU 210 determines whether or not the determination target device is connected to the determination target device. It is determined that re-establishment processing will be performed. If the encryption method currently established with the determination target device is included in the encryption method list of the target server (S140: YES), in S150, the CPU 210 determines whether or not the determination target device It is determined that no re-establishment process is performed.

  In S155, the CPU 210 determines whether or not all devices specified in S130 have been processed as determination target devices. When there is an unprocessed device (S155: NO), the CPU 210 returns to S135 and selects an unprocessed device as a determination target device. When all the devices have been processed (S155: YES), the CPU 210 ends the re-establishment determination process.

  When the re-establishment determination process in S34 of FIG. 3 is completed, the process proceeds to S36 of FIG. If it is determined in the re-establishment determination process that the communication re-establishment process with the device 100 is performed (S36: YES), in S38, the CPU 210 uses the currently established communication, A re-establishment request is transmitted to the device 100. The re-establishment request is transmitted as communication between applications using, for example, XMPP communication.

  In S <b> 39, the CPU 210 disconnects the currently established communication with the device 100. For example, the logical communication path in the TCP layer or the SSL / TLS layer is disconnected mainly by the relay server 200. As a modification, in S38, the CPU 210 may transmit a request for disconnecting the currently established communication to the device 100 together with the re-establishment request. In this case, the currently established communication is disconnected mainly by the device 100 that has received the disconnection request. As another modification, another encrypted communication may be re-established while maintaining the currently established communication without disconnecting the currently established communication.

  When the device 100 receives the re-establishment request, in S40, the CPU 110 of the device 100 transmits a communication start request similar to that in S10 of FIG. 1 to the relay server 200 in response to the re-establishment request. The communication start request includes the encryption method list CL1 of FIG.

  When the relay server 200 receives the encryption method list CL1, in S42, the CPU 210 selects one of the plurality of encryption methods A and C (FIG. 2A) shown in the encryption method list CL1. Select the encryption method used. Specifically, since the communication start request includes the global IP address as the device ID of the device 100 as the IP address of the transmission source, the CPU 210 acquires the global IP address. Then, based on the global IP address as the device ID, the device table DT is referred to, and the usage server of the device 100, in the example of FIG. Further, the CPU 210 refers to the server table ST to identify the encryption method list of the specified use server, and in the example of FIG. 4, the encryption method list CL3 of the service providing server 300 is specified. Then, unlike S12 in FIG. 3, the CPU 210 selects a used encryption method based on the encryption methods C and D shown in the encryption method list CL3 of the specified service providing server 300. Specifically, the CPU 210 uses the same encryption as any of the encryption methods C and D shown in the encryption method list CL3 among the encryption methods A and C shown in the encryption method list CL1 of the service providing server 300. Select the conversion method. Therefore, in this embodiment, the encryption method C included in both of the two encryption method lists CL1 and CL3 is selected.

  Note that if none of the encryption methods shown in the encryption method list of the service providing server 300 is included in the encryption method list of the device 100 in S42, the CPU 210 uses one encryption method for use. The method cannot be selected. When the used encryption method cannot be selected, the CPU 210 does not allow establishment of communication between the device 100 and the relay server 200. The same applies to S82 described later. Therefore, for example, in this case, the CPU 210 transmits an error notification to, for example, both the device 100 and the relay server 200 without performing the processing after S44.

  In S <b> 44, the CPU 210 transmits a notification of the used encryption method, in this embodiment, the encryption method C, to the device 100. Note that the communication in S40 and S44 is communication between SSL / TLS layers.

  When the device 100 receives the notification of the used encryption method, a communication establishment process is performed between the device 100 and the relay server 200 in S46. That is, communication for establishing encrypted communication using the encryption method C, which is the encryption method used, between the device 100 and the relay server 200 is executed according to SSL / TLS. Further, communication for establishing XMPP communication is executed in accordance with XMPP on the established encrypted communication. As a result, communication between the device 100 and the relay server 200 is reestablished.

  In S48, the CPU 110 uses the encrypted communication established and the XMPP communication established on the encrypted communication to transmit the device ID and the use server ID in the same way as in S18 of FIG. Send to. The relay server 200 receives these device IDs and the usage server ID, and confirms that communication has been reestablished with the device (device 100 in this embodiment) to which communication should be reestablished. Can be confirmed at the application level.

  If it is determined in the re-establishment determination process in S34 that the communication re-establishment process with the device 100 is not performed (S36: NO), the processes in S38 to S48 are not performed.

  In S50, the CPU 210 of the relay server 200 transmits the status request received from the service providing server 300 in S30 to the device 100. When the device 100 receives the status request, in S52, the CPU 110 acquires its own status in response to the status request. In S <b> 54, the CPU 110 transmits the status notification to the relay server 200. Note that S50 and S54 are performed using the re-established communication when the communication between the device 100 and the relay server 200 is re-established. Even after S54, the encrypted communication between the relay server 200 and the device 100 and the XMPP communication established on the encrypted communication are maintained.

  When the relay server 200 receives the status notification, the CPU 210 transmits the status notification to the service providing server 300 in S56. As a result, the service providing server 300 can acquire the status of the device to be managed. These statuses are transmitted to, for example, a terminal device of a manager of a device that uses the service providing server 300. When the status notification is transmitted to the service providing server 300, the encrypted communication between the relay server 200 and the service providing server 300 is disconnected. Note that the communication in S48, S50, S54, and S56 is communication between applications of the devices 100, 200, and 300.

  6 and 7 are sequence diagrams illustrating an example of communication in the system 1000. FIG. This sequence diagram is an example when the device 100 accesses the relay server 200 after the encryption method list CL3 of the service providing server 300 is registered in the relay server 200.

  First, in a state where communication is not established between the device 100 and the relay server 200, the service providing server 300 acquires the status of a plurality of devices to be managed including the device 100 so as to acquire the status of the relay server 200. To access. Specifically, in S60 to S68 of FIG. 6, the same processing as S22 to S32 of FIG. 3 is performed. As a result, encrypted communication using the encryption method C is established between the relay server 200 and the service providing server 300, and the encryption method of the service providing server 300 is stored in the server table ST of the relay server 200. List CL3 is registered.

  In S69, as in S34 in FIG. 3, the CPU 210 executes the re-establishment determination process in FIG. In the re-establishment determination process of S69, since communication is not established between the device 100 and the relay server 200, the device 100 is not specified in S130 of FIG. For this reason, in the re-establishment determination process in S69, the re-establishment determination for the device 100 is not performed.

  In S <b> 70, the CPU 210 transmits a status acquisition impossibility notification to the service providing server 300. The notification that the status cannot be acquired is a notification that indicates that the status cannot be acquired from the device 100 because communication is not established between the device 100 and the relay server 200. When the notification that the status cannot be acquired is transmitted to the service providing server 300, the encrypted communication between the relay server 200 and the service providing server 300 is disconnected.

  Thereafter, for example, it is assumed that the device 100 is turned on and the device 100 accesses the relay server 200. Specifically, in S71 to S76 of FIG. 6, the same processing as S10 to S20 of FIG. 3 is performed. As a result, encrypted communication using the encryption method A and XMPP communication on the encrypted communication are established between the device 100 and the relay server 200. In addition, the device 100 is registered in the device table DT of the relay server 200.

  In S77 of FIG. 7 that follows, the CPU 210 executes the re-establishment determination process of FIG. In the re-establishment determination process of S77, since the encryption method list CL3 of the service providing server 300 is registered in the server table ST at this time, the encryption method list CL3 has already been registered in S110 of FIG. It is judged that there is. Since the encryption method used in the communication established between the device 100 and the relay server 200 is the encryption method A, in S115 of FIG. Then, it is determined that there is no encryption method used in communication established with the target device (S115: NO). As a result, it is determined in S120 that the communication re-establishment process is performed with the device 100. If the encryption method used in the communication established between the device 100 and the relay server 200 is the encryption method C, in S115 of FIG. Then, it is determined that there is an encryption method used in the communication established with the target device (S115: YES). In this case, it is determined in S125 of FIG. 5 that communication re-establishment processing is not performed with the device 100.

  If it is determined in the re-establishment determination process of S77 of FIG. 7 that communication with the device 100 is re-established (S78: YES), the same processes as S38-S48 of FIG. 4 are performed in S79-S85. Is done. As a result, communication between the device 100 and the relay server 200 is reestablished.

  If it is determined in the re-establishment determination process of S77 that the re-establishment process of communication with the device 100 is not performed (S78: NO), the processes of S79 to S85 are not performed.

  Thereafter, when there is an access from the service providing server 300 to the relay server 200, the processing after S22 in FIG. 3 is performed.

  According to the present embodiment described above, the relay server 200 uses one or more first encryption methods (specifically, the encryption methods C shown in the encryption method list CL3) that the service providing server 300 can use. , D) is used to establish first encrypted communication with the service providing server 300 using the encryption method selected from (D) (S22 to S28 in FIG. 3, S60 to S66 in FIG. 6). Then, the relay server 200 receives the encryption method list CL1 indicating a plurality of encryption methods that can be used by the device 100 from the device 100 (S40 in FIG. 4 and S81 in FIG. 7). Then, after the first encrypted communication is established, the relay server 200 uses the plurality of first encryption methods that can be used by the service providing server 300 to perform a plurality of operations shown in the encryption method list CL1. The second encryption method is selected from the encryption methods (specifically, encryption methods A and C) (S42 in FIG. 4 and S82 in FIG. 7). The selected second encryption method is the same encryption method (specifically, encryption method C) as any one of the one or more first encryption methods. Then, the second encrypted communication is established with the device 100 using the second encryption method (S46 in FIG. 4, S84 in FIG. 7). Then, the relay server 200 relays communication between the service providing server 300 and the device 100 using the first encrypted communication and the second encrypted communication (S50, S54, and S56 in FIG. 4).

  According to the above configuration, the second encryption method of the second encrypted communication to be established with the device 100 is selected based on one or more first encryption methods that can be used by the service providing server 300. The Then, the same encryption method as the first encryption method is selected as the second encryption method. Therefore, it is possible to suppress a decrease in the security level of the second encryption method compared to the first encryption method. Therefore, when the relay server 200 relays communication between the device 100 and the service providing server 300, the security level of communication between the device 100 and the service providing server 300 is set to a necessary level (for example, service provision). The level requested by the server 300 can be maintained.

  More specifically, one or more first encryption methods shown in the encryption method list CL3 are set based on the security level that the operator of the service providing server 300 thinks should be maintained. . However, the second encryption method of the second encrypted communication between the device 100 and the relay server 200 is different from any one of the one or more first encryption methods, in particular, the one or more first items. Assume that the encryption method has a lower security level than the encryption method. Then, the security level of communication between the device 100 and the service providing server 300 performed via the relay server 200 is lower than the security level that the operator of the service providing server 300 thinks should be maintained. In the present embodiment, the second encryption method used for the second encrypted communication is the same encryption method as the one or more first encryption methods. As a result, the security level of communication between the device 100 and the service providing server 300 performed via the relay server 200 can be maintained at the security level that the operator of the service providing server 300 thinks should be maintained.

  The relay server 200 registers the encryption method list CL3 of the service providing server 300 every time encrypted communication with the service providing server 300 is established (S32 in FIG. 3, S68 in FIG. 6). As a result, one or more first encryption methods that can be used by the service providing server 300 can always be properly recognized. Therefore, for example, even when the service providing server 300 changes one or more usable first encryption methods for security enhancement or the like, the device 100 performed via the relay server 200 is used. The security level of communication with the service providing server 300 can be maintained at a security level that the operator of the service providing server 300 thinks should be maintained.

  Further, the relay server 200 uses a third encryption method (specifically, encryption method A) different from the second encryption method (specifically, encryption method C) to communicate with the device 100. In the meantime, the third encrypted communication is established (S16 in FIG. 3, S74 in FIG. 6). The relay server 200 receives specific information (specifically, a device ID and a usage server ID) from the device 100 using the third encrypted communication (S18 in FIG. 3 and S75 in FIG. 6). Then, after receiving the specific information, the relay server 200 establishes the second encrypted communication (S46 in FIG. 4, S84 in FIG. 7).

  Thus, even after the third encrypted communication is once established, the second encrypted communication is established thereafter. Therefore, for example, even when the security level of the third encrypted communication is relatively low, the security of communication between the device 100 and the service providing server 300 is established by newly establishing the second encrypted communication. The level can be maintained at the required level.

  Further, the relay server 200 compares one or more first encryption methods (encryption methods shown in the encryption method list CL3) with the third encryption method in the re-establishment determination process of FIG. (S115 and S140 in FIG. 5). As a result, when the third encryption method is the same encryption method as the first encryption method (S115: YES, S140: YES), the re-establishment process is not performed (S125, S150). That is, the second encrypted communication is not established and the third encrypted communication is maintained. On the other hand, when the third encryption method is different from the first encryption method (S115: NO, S140: NO), re-establishment processing is performed (S120, S145). That is, re-establishment processing is performed with the device 100, and the second encrypted communication is established (S46 in FIG. 4 and S84 in FIG. 7). As a result, when it is not necessary to establish the second encrypted communication, the second encrypted communication is not established, so that it is possible to suppress the execution of useless processing.

  The relay server 200 is a device to which the relay server 200 should relay communication using specific information (specifically, device ID, use server ID) received from the device 100 using the third encrypted communication. 100 and the service providing server 300 are associated (S20 in FIG. 3, S76 in FIG. 6, device table DT). As a result, for example, even when the relay server 200 is an apparatus that relays communication between a plurality of devices and a plurality of service providing servers, the device 100 and the service providing server 300 can be associated appropriately. Therefore, after that, it is possible to appropriately determine whether to re-establish communication between the device 100 and the service providing server 300.

  Further, the relay server 200 establishes the second encrypted communication (S46 in FIG. 4, S84 in FIG. 7) after the third encrypted communication is disconnected (S39 in FIG. 4, S80 in FIG. 7). In this way, the third encrypted communication having a problem with the security level is disconnected, so that the security level of communication between the device 100 and the service providing server 300 can be more reliably maintained at a necessary level. .

  Further, the relay server 200 associates an encryption method list CL3 indicating one or more first encryption methods with an identifier (specifically, a server ID) indicating the service providing server 300 in the server table ST. Store (S32 in FIG. 3, S68 in FIG. 6). The relay server 200 receives an identifier (specifically, a use server ID) and a device identifier (device ID) indicating the service providing server 300 from the device 100 (S18 in FIG. 3 and S75 in FIG. 6). The relay server 200 uses these identifiers in the re-establishment determination process of FIG. 5 to specify the encryption method list CL3 to be used for the determination, that is, specifies one or more first encryption methods. . In the subsequent re-establishment process, the second encryption method is selected based on the specified first encryption method (S42 in FIG. 4 and S82 in FIG. 7).

  According to the above configuration, for example, even when the relay server 200 is an apparatus that relays communication between a plurality of devices and a plurality of service providing servers, the relay server 200 includes the identifier indicating the service providing server 300 and the device 100. Since an appropriate first encryption method can be specified using the identifier, an appropriate second encryption method can be selected.

  The first encrypted communication and the second encrypted communication are used for communication between applications belonging to the application layer (specifically, transmission / reception of status requests and status notifications). Transmission / reception of the encryption method list CL3 is performed using communication in a lower layer (specifically, SSL / TLS layer) than the application. As a result, the security level of communication between applications can be maintained at a necessary level without providing a special mechanism for the applications.

  Further, the relay server 200 receives information indicating the status of the device 100 from the device 100 using the second encrypted communication (S54 in FIG. 4), and indicates the status using the first encrypted communication. Information is transmitted to the service providing server 300 (S56 in FIG. 4). Since the status of the device 100 is used for billing, for example, there is much information that should be treated as confidential information. In this embodiment, the relay server 200 can relay these pieces of information through communication with an appropriate security level.

B. Second embodiment:
The non-volatile storage device 220 of the relay server 200 of the second embodiment stores reference information RI indicated by a broken line in FIG. The reference information RI is information indicating the security level order of a plurality of types of algorithms belonging to at least one item among a plurality of items of algorithms included in the encryption method.

  FIG. 8 is a diagram illustrating an example of the reference information RI. The reference information RI indicates the order of security levels for the key exchange algorithm and the encryption algorithm. For example, regarding the key exchange algorithm, it is shown that the security level is higher in the order of “ECDHE”> “DHE”> “RSA”. As for the encryption algorithm, it is shown that the security level is higher in the order of “AES”> “3DES”> “DES”. Note that the level of security is not uniquely determined, and may vary depending on, for example, what kind of threat is important for security. In addition, the level of security level may change in the future due to the discovery of a vulnerability of a specific algorithm. For this reason, the reference information RI is periodically reviewed by the operator of the relay server 200.

  In the second embodiment, reference information RI is used in the re-establishment determination process. FIG. 9 is a flowchart of the re-establishment determination process according to the second embodiment. In the re-establishment determination process of FIG. 9, S115b and S140b are executed instead of S115 and S140 of the re-establishment determination process of FIG. Other processes of the re-establishment determination process of FIG. 9 are the same as the re-establishment determination process of FIG.

  In S115b, the encryption method currently established with the target device (eg, device 100) is added to the encryption method list (eg, encryption method list CL3) of the usage server (eg, service providing server 300). It is determined whether or not the security level is higher than the indicated encryption method.

  An example of a specific method for this determination will be described. The CPU 210 identifies the current key exchange algorithm and encryption algorithm, that is, the key exchange algorithm and encryption algorithm included in the currently established encryption method. For example, if the currently established encryption method is encryption method A (FIG. 2A), “RSA” is specified as the key exchange algorithm and “AES” is specified as the encryption algorithm. The Further, the CPU 210 has the lowest security level of the key exchange algorithm and encryption algorithm at the lowest level of the use server, that is, the key exchange algorithm of one or more encryption methods shown in the encryption method list of the use server. The algorithm and the algorithm with the lowest security level among the cryptographic algorithms are identified. For example, when the encryption method list of the use server is the encryption method list CL3 (FIG. 2D) of the service providing server 300, “DHE” is specified as the lowest level key exchange algorithm and the encryption is performed. “AES” is specified as the algorithm.

  The CPU 210 refers to the reference information RI (FIG. 8), and the security level of the current key encryption algorithm is equal to or higher than the lowest key encryption algorithm of the use server, and the security level of the current encryption algorithm is It is judged whether or not the encryption algorithm is at least the lowest level of the usage server. When the determination result is affirmative, the CPU 210 determines that the currently established encryption method is a security level higher than the encryption method indicated in the encryption method list of the use server. When the determination result is negative, the CPU 210 determines that the currently established encryption method is at a lower security level than the encryption method indicated in the encryption method list of the use server.

  For example, when the currently established encryption method is the encryption method A (FIG. 2A) and the encryption method list of the use server is the encryption method list CL3 (FIG. 2D) think of. In this case, the key exchange algorithm “RSA” of the encryption method A has a lower security level than the lowest-level key exchange algorithm “DHE” in the encryption method list CL3 (reference information RI in FIG. 9). Therefore, in this case, it is determined that the currently established encryption method has a lower security level than the encryption methods indicated in the encryption method list of the use server.

  In S140b, the CPU 210 determines that the encryption method currently established with the device to be determined (for example, the service providing server 300) is the encryption method list (for example, the service providing server 300). It is determined whether or not the security level is equal to or higher than the encryption method indicated in the encryption method list CL3). A specific determination method is the same as 115b described above.

  Furthermore, the second embodiment differs from the first embodiment in the method of selecting the encryption method to be used at the time of re-establishing S42 in FIG. 4 and S82 in FIG.

  In S42 and S82, the CPU 210 selects one used encryption method from among a plurality of encryption methods indicated in the encryption method list CL1 received from the device 100. At this time, as in the first embodiment, the CPU 210 determines the encryption method to be used based on the encryption method indicated in the encryption method list CL3 of the service providing server 300 that is the use server registered in the server table ST. select. However, the specific method is different from the first embodiment. In the second embodiment, the CPU 210 has a security level equal to or higher than the encryption method shown in the encryption method list CL3 of the service providing server 300 among the plurality of encryption methods shown in the encryption method list CL1 of the device 100. Select an encryption method.

  Specifically, the CPU 210 identifies the lowest-level key exchange algorithm and encryption algorithm of the service providing server 300 as in the above-described process of S115b. The CPU 210 includes a key exchange algorithm having a security level equal to or higher than the identified lowest level key exchange algorithm among the plurality of encryption methods indicated in the encryption method list CL1 received from the device 100, and Then, an encryption method including an encryption algorithm having a security level equal to or higher than the lowest level encryption algorithm is selected as the used encryption method.

  For example, as described above, in the service providing server 300, the lowest level key exchange algorithm is “DHE”, and the lowest level encryption algorithm is “AES”. Therefore, among the encryption methods A and C shown in the encryption method list CL1, the encryption method C is selected as the used encryption method.

  In the second embodiment, in S42 and S82, an encryption method having a security level higher than the encryption method shown in the encryption method list of the service providing server 300 is included in the encryption method list of the device 100. If not, the CPU 210 cannot select one used encryption method. When the used encryption method cannot be selected, the CPU 210 does not allow communication to be established between the device 100 and the relay server 200 as in the first embodiment.

  According to the second embodiment described above, as in the first embodiment, the relay server 200 uses one or more first encryption schemes (specifically, encryption schemes) that the service providing server 300 can use. The first encrypted communication is established with the service providing server 300 using the encryption method selected from the encryption methods C and D shown in the list CL3 (S22 to S28 in FIG. 3, FIG. 6). S60 to S66). Then, the relay server 200 receives the encryption method list CL1 indicating a plurality of encryption methods that can be used by the device 100 from the device 100 (S40 in FIG. 4 and S81 in FIG. 7). Then, after the first encrypted communication is established, the relay server 200 uses the plurality of first encryption methods that can be used by the service providing server 300 to perform a plurality of operations shown in the encryption method list CL1. The second encryption method is selected from the encryption methods (specifically, encryption methods A and C) (S42 in FIG. 4 and S82 in FIG. 7). Then, the second encrypted communication is established with the device 100 using the second encryption method (S46 in FIG. 4, S84 in FIG. 7). The relay server 200 relays communication between the service providing server 300 and the device 100 using the first encrypted communication and the second encrypted communication (S50, S54, S56 in FIG. 4). Here, in the second embodiment, the selected second encryption method is an encryption method having a security level equal to or higher than one or more first encryption methods. As a result, as in the first embodiment, the security level of communication between the device 100 and the service providing server 300 can be maintained at a necessary level. Furthermore, the second encryption method is not limited to the same encryption method as the first encryption method, and may be any encryption method having a security level higher than that of the first encryption method. For example, the device can be used. Since there is no encryption method that can be selected among the various encryption methods, it is possible to prevent the encryption method from being selected.

  Further, according to the second embodiment, the relay server 200 determines that the encryption method being established with the device (that is, the third encryption method) is the first encryption in the re-establishment determination process of FIG. If the encryption method has a security level equal to or higher than the method (S115b: YES, S140b: YES), the re-establishment process is not performed (S125, S150). That is, the second encrypted communication is not established and the third encrypted communication is maintained. On the other hand, when the third encryption method is an encryption method whose security level is lower than that of the first encryption method (S115b: NO, S140b: NO), re-establishment processing is performed (S120, S120). That is, re-establishment processing is performed with the device 100, and the second encrypted communication is established (S46 in FIG. 4 and S84 in FIG. 7). As a result, when it is not necessary to establish the second encrypted communication, the second encrypted communication is not established, so that it is possible to suppress the execution of useless processing.

  Further, according to the second embodiment, an algorithm included in the first encryption method for two items (specifically, a key exchange algorithm and an encryption algorithm) among a plurality of items of algorithms of the encryption method. The encryption method including the algorithm having the above security level is selected as the second encryption method at the time of re-establishment. Therefore, communication between the device 100 and the relay server 200 with respect to two items of the multi-item algorithm, that is, between the device 100 and the service providing server 300 performed via the relay server 200 is performed. The security level of communication can be maintained at a required level.

B. Variations:
(1) In the above embodiment, once the third encrypted communication is established between the device 100 and the relay server 200 (for example, S71 to S74 in FIG. 6), re-establishment is performed. 2 Encrypted communication is established (for example, S79 to S84 in FIG. 7). This is because the relay server 200 first recognizes the usage server of the device 100 when the application of the relay server 200 receives the device ID and the usage server ID transmitted in S75 using the third encrypted communication. This is because it is necessary to establish the third encrypted communication once. Instead of this, for example, the device 100 may include the server ID and the use server ID in the communication start request in S71 and transmit the same to the relay server 200. That is, transmission / reception of the server ID and the use server ID may be performed by SSL / TLS layer communication. In this way, the relay server 200 can recognize the use server of the device 100 at this point and refer to the encryption method list of the registered use server. Therefore, at the time of S72, the second encryption method may be selected based on the first encryption method of the use server. In this case, the second encrypted communication can be established from the beginning without establishing the third encrypted communication.

(2) In the re-establishment determination process of FIG. 5 of the first embodiment, when the encryption list of the use server has been registered, the third encryption method is shown in the encryption method list of the use server. Whether or not re-establishment is to be performed is determined by determining whether or not it is the same as one encryption method (S115 and S140 in FIG. 5). Alternatively, if the encryption list of the usage server is already registered, re-establishment may always be performed regardless of the type of the third encryption method.

(4) In the above-described embodiment, the device ID and the usage server ID are transmitted from the device 100 to the relay server 200 (S18 in FIG. 3), and the usage server ID and the usage server ID are associated with each other, and the device table DT. (S20 in FIG. 3). Thereby, the relay server 200 can identify the correspondence between the device 100 and the encryption method list CL3 of the service providing server 300, that is, one or more first encryption methods of the service providing server 300 (FIG. 5). S130, S105). Instead, the device ID to be managed may be transmitted together with the server ID from the service providing server 300 in S30 of FIG. The device ID to be managed may be registered in the server table ST together with the server ID and the server encryption list. Thus, the correspondence between the device 100 and one or more first encryption methods of the service providing server 300 may be specified. Alternatively, the designation information transmitted from the service providing server 300 described above may be registered in the server table ST together with the server ID and the server encryption list. Thus, the correspondence between all devices specified by the specification information and one or more first encryption methods of the service providing server 300 may be specified.

(5) In the first embodiment, the second encryption method that is completely the same as the first encryption method that can be used by the service providing server 300 is selected in S42 of FIG. 4 or S82 of FIG. Instead of this, the second encryption method including the same algorithm as the algorithm included in the first encryption method for a part of the plurality of algorithms, for example, the key exchange algorithm and the encryption algorithm, is used. You may choose.

  In the second embodiment, one or more first encryptions that can be used by the service providing server 300 for two items of the plurality of algorithms in S42 of FIG. 4 and S82 of FIG. A second encryption method having a security level equal to or higher than the method is selected. Instead of this, even if a second encryption method having a security level equal to or higher than one or more first encryption methods is selected for all items in the algorithm of a plurality of items or for one item. good.

  In general, for at least one item of the plurality of algorithms, the second encryption method including the same algorithm as the algorithm included in the one or more first encryption methods, or the one or more first items It is preferable that the second encryption method having a security level of one encryption method or more is selected. In this way, the security level of communication between the device 100 and the service providing server 300 can be maintained at a necessary level for at least one item of the multiple item algorithm.

(6) In the above-described embodiment, in the process for re-establishing communication (S46 in FIG. 4 and S84 in FIG. 7), the same process as when establishing communication for the first time is performed. Instead, for example, when it is not necessary to change the authentication algorithm at the time of re-establishment, for example, by performing only other processing such as key exchange again without performing authentication of the relay server 200 again, Communication may be reestablished.

(7) Information transmitted / received between the application of the device 100 and the service providing server 300 via the relay server 200 is not limited to information indicating the status, but may be other data such as image data or print data. It may be information.

(8) The relay server 200 and the service providing server 300 may be a so-called cloud server including a plurality of devices (for example, computers) that can communicate with each other via a network.

(9) In each of the above embodiments, a part of the configuration realized by hardware may be replaced with software, and conversely, part or all of the configuration realized by software is replaced with hardware. You may do it.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

    70 ... LAN, 80 ... Internet, 100 ... Device, 110 ... CPU, 120 ... Non-volatile storage device, 130 ... Volatile storage device, 131 ... Buffer area, 140 ... Printer part, 150 ... Scanner part, 160 ... Operation part, 170 ... Display part, 180 ... Network IF, 200 ... Relay server, 210 ... CPU, 220 .. .Non-volatile storage device, 230 ... volatile storage device, 231 ... buffer area, 280 ... network IF, 300 ... service providing server, 310 ... CPU, 320 ... non-volatile storage Device, 330 ... volatile storage device, 331 ... buffer area, 380 ... network IF, 1000 ... system

Claims (14)

A computer program for a relay device,
A first encrypted communication is established with the service providing apparatus using an encryption method selected from one or more first encryption methods that can be used by a service providing apparatus that provides a specific service. A first establishment function;
A first reception function for receiving a method list indicating a plurality of encryption methods usable by the communication device from the communication device;
A selection function for selecting a second encryption method from a plurality of encryption methods shown in the method list based on the first encryption method after the establishment of the first encrypted communication; The selected second encryption method is one of the same encryption method as the first encryption method and an encryption method having a security level higher than that of the first encryption method. Select function,
A second establishment function for establishing a second encrypted communication with the communication device using the second encryption method;
A relay function for relaying communication between the service providing apparatus and the communication apparatus using the first encrypted communication and the second encrypted communication;
A computer program that causes a computer to realize The computer program according to claim 1, further comprising:
A third establishment function for establishing a third encrypted communication with the communication device using a third encryption method different from the second encryption method;
A second receiving function for receiving specific information from the communication device using the third encrypted communication;
Is realized on a computer,
The computer program, wherein the second establishment function establishes the second encrypted communication after receiving the specific information. The computer program according to claim 2, further comprising:
Allowing a computer to realize a comparison function for comparing the first encryption method and the third encryption method;
When the third encryption method is the same encryption method as the first encryption method, the second establishment function does not establish the second encryption communication, and does not establish the second encryption communication. Maintain communication,
When the third encryption method is an encryption method different from the first encryption method, the second establishment function establishes the second encrypted communication. The computer program according to claim 2, further comprising:
Allowing a computer to realize a comparison function for comparing the first encryption method and the third encryption method;
When the third encryption method is an encryption method having a security level equal to or higher than the first encryption method, the second establishment function does not establish the second encryption communication, and does not establish the second encryption communication. 3 Maintain encrypted communication,
When the third encryption method is an encryption method having a security level lower than that of the encryption method, the second establishment function establishes the second encrypted communication. The computer program according to any one of claims 2 to 4, further comprising:
A computer program that causes a computer to realize an association function for associating the communication device with which the relay device should relay communication with the service providing device, using the specific information. The computer program according to any one of claims 2 to 5, further comprising:
The second establishment function is a computer program that establishes the second encrypted communication after the third encrypted communication with the communication device is disconnected. The computer program according to claim 1, further comprising:
A storage function for storing the first encryption method and at least one of a service identifier indicating the service providing apparatus and a device identifier indicating the communication apparatus in association with each other;
A third receiving function for receiving at least one of the service identifier and the device identifier from the communication device;
A specifying function for specifying the first encryption method using at least one of the received service identifier and the device identifier;
Is realized on a computer,
The selection function is a computer program that selects the second encryption method based on the identified first encryption method. A computer program according to any one of claims 1 to 3 and 5 to 7,
The first encryption method and the second encryption method exchange an authentication algorithm for device authentication, an encryption algorithm for encrypting communication data, and an encryption key used in the encryption algorithm. Including a key exchange algorithm, and a hash algorithm used in at least one of the authentication algorithm, the encryption algorithm, and the key exchange algorithm,
The computer program, wherein the selection function selects the second encryption method including the same algorithm as the algorithm included in the first encryption method for at least one item of the plurality of items of algorithms. A computer program according to any one of claims 1, 2, 4 to 6,
The first encryption method and the second encryption method exchange an authentication algorithm for device authentication, an encryption algorithm for encrypting communication data, and an encryption key used in the encryption algorithm. Including a key exchange algorithm, and a hash algorithm used in at least one of the authentication algorithm, the encryption algorithm, and the key exchange algorithm,
The computer program for selecting the second encryption method including an algorithm having a security level equal to or higher than an algorithm included in the first encryption method for at least one item of the plurality of items of the algorithm . A computer program according to any one of claims 1 to 9,
The first encrypted communication and the second encrypted communication are used for communication between applications belonging to the application layer,
The first reception function is a computer program that receives the method list using communication in a lower layer than the application. A computer program according to claim 7,
The third reception function receives at least one of the service identifier and the device identifier using communication between applications belonging to an application layer,
The first reception function is a computer program that receives the method list using communication in a lower layer than the application. A computer program according to claim 10 or 11,
A computer program in which a protocol for receiving the method list is SSL (Secure Sockets Layer) / TLS (Transport Layer Security). A computer program according to any one of claims 1 to 12,
The relay function is
Using the second encrypted communication, receiving information indicating the status of the communication device from the communication device,
A computer program for transmitting information indicating the status to the service providing apparatus using the first encrypted communication. A relay device,
A first encrypted communication is established with the service providing apparatus using an encryption method selected from one or more first encryption methods that can be used by a service providing apparatus that provides a specific service. A first establishment unit;
A first receiving unit that receives, from a communication device, a method list indicating a plurality of encryption methods that can be used by the communication device;
A selection unit that selects a second encryption method from a plurality of encryption methods shown in the method list based on the first encryption method after the first encrypted communication is established; The selected second encryption method is one of the same encryption method as the first encryption method and an encryption method having a security level higher than that of the first encryption method. A selection section;
A second establishing unit for establishing second encrypted communication with the communication device using the second encryption method;
A relay unit that relays communication between the service providing apparatus and the communication apparatus using the first encrypted communication and the second encrypted communication;
A relay device comprising:

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