Patent Publication Number: US-2017357825-A1

Title: Information processing terminal which communicates confidential information, information processing system, computer readable recording medium having program stored thereon, and control method, as well as information processing terminal which transmits control signal to external device and computer readable recoding medium having program stored thereon

Description:
This application is based on Japanese Patent Application No. 2016-118075 filed with the Japan Patent Office on Jun. 14, 2016, the entire content of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This disclosure relates to control of an information processing terminal and more particularly to control of an information processing terminal which wirelessly communicates. 
     Description of the Related Art 
     With the tendency toward Internet on Things (IoT) in recent years, use of wireless communication equipment has been promoted. Wireless communication permits easy construction of networks without using physical cables, whereas it is vulnerable to impersonation by a malicious third party. 
     For a technique to suppress impersonation, for example, Japanese Laid-Open Patent Publication No. 2014-082716 discloses a configuration in which possibility of spoofed connection is lowered without modifying a hardware configuration which increases battery drain. More specifically, according to this technique, when first identification confidential information (a media access control (MAC) address) included in a first pairing request packet and second identification confidential information included in a second pairing request packet satisfy a predetermined condition, a terminal which has wirelessly transmitted the second pairing request packet is registered as a terminal which wirelessly communicates confidential information through a layer higher than a confidential information link layer. 
     In connection with a technique for securely copying confidential information, for example, Japanese Laid-Open Patent Publication No. 2011-071593 discloses a portable information terminal system which copies a program of a portable information terminal serving as a master into another portable information terminal without using a copy jig device. More specifically, the portable information terminal system establishes wireless connection through a wireless local area network (LAN) to another portable information terminal with which pairing has been specified based on authentication under a public key cryptosystem with the use of an electronic certificate and communicates therewith under symmetric key cryptography by distributing a symmetric encryption key under the public key cryptosystem. 
     In addition, such a scheme that authentication is performed while buttons provided in two terminals in wireless communication with each other are simultaneously pressed and communication only with a successfully authenticated pair is carried out has also been known as a technique relating to other security communication. 
     SUMMARY OF THE INVENTION 
     The techniques disclosed in Japanese Laid-Open Patent Publications Nos. 2014-082716 and 2011-071593, however, are vulnerable to impersonation by a malicious third party if authentication information such as key information/input information is stolen. Since authentication information is normally configured to be complicated from a point of view of ensured security, it is difficult for a user to memorize the authentication information. Therefore, the user manages the authentication information by using notes or the like. From a point of view of security, however, it is not preferable to take notes of authentication information. 
     The scheme that authentication is performed while buttons provided in two terminals in wireless communication with each other are simultaneously pressed is also vulnerable to impersonation based on radio waves output from equipment while the buttons are pressed. 
     The present disclosure was made to solve the problems as described above and an object in one aspect is to provide an information processing terminal which can suppress impersonation while convenience of a user is ensured. 
     According to one embodiment, an information processing terminal which communicates confidential information with a sensor terminal including a first biological sensor which measures biological information of a first type is provided. The information processing terminal includes a reception device which receives a result of measurement by the first biological sensor from the sensor terminal, a second biological sensor which measures biological information of the first type, and a control device configured to communicate confidential information with the sensor terminal when the result of measurement by the first biological sensor satisfies a predetermined condition for a result of measurement by the second biological sensor. 
     Preferably, the control device is configured to be able to switch between a first mode in which the confidential information is communicated with the sensor terminal when the result of measurement by the first biological sensor satisfies the predetermined condition and a second mode in which the confidential information is communicated with the sensor terminal without comparison between the result of measurement by the first biological sensor and the result of measurement by the second biological sensor. The control device communicates the confidential information with the sensor terminal in the first mode when a security level of the confidential information to be communicated with the sensor terminal is equal to or higher than a predetermined level. 
     Further preferably, a storage device which stores the result of measurement by the second biological sensor is further included. The control device encrypts the confidential information with a prescribed result of measurement stored in the storage device and transmits the encrypted confidential information to the sensor terminal in the second mode when the security level of the confidential information to be transmitted to the sensor terminal is lower than the predetermined level. 
     Preferably, the control device communicates the confidential information with the sensor terminal through short-range wireless communication when the security level of the confidential information to be communicated with the sensor terminal is equal to or higher than the predetermined level. 
     Further preferably, the control device communicates the confidential information with the sensor terminal through wireless communication higher in bit rate than the short-range wireless communication when the security level of the confidential information to be communicated with the sensor terminal is lower than the predetermined level. 
     Further preferably, the control device verifies whether or not the confidential information is present in an external device configured to be able to communicate with the sensor terminal when the security level of the confidential information to be transmitted to the sensor terminal is lower than the predetermined level. The control device transmits a control signal having the external device transfer the confidential information to the sensor terminal to any one of the external device and the sensor terminal when presence of the confidential information in the external device is verified. 
     Further preferably, the information processing terminal is configured to be able to communicate with an external device. The control device is configured to receive the security level of the confidential information from the sensor terminal in receiving the confidential information from the sensor terminal and to transfer the confidential information received from the sensor terminal to the external device when the security level of the confidential information is lower than the predetermined level. 
     Further preferably, a storage device is further included. The control device is configured to have the storage device store prescribed information when the confidential information received from the sensor terminal is transferred to the external device. The prescribed information includes at least any one of information on connection to the external device, information on an area of storage of the confidential information in the external device, and information used for logging in the external device. 
     Preferably, the control device includes at least one of a component which transmits information on the security level of the confidential information to be transmitted to the sensor terminal to the sensor terminal and a component which requests from the sensor terminal, information on the security level of the confidential information received from the sensor terminal. 
     Preferably, an operation acceptance device which accepts input of information is further included. The control device sets the security level of the confidential information to be communicated with the sensor terminal based on information input to the operation acceptance device. 
     Preferably, an operation acceptance device which accepts input of information is further included. The control device determines the security level of the confidential information to be communicated with the sensor terminal based on any one of information on a storage area where the confidential information is stored, first security information added to the confidential information, and second security information input to the operation acceptance device in communication of the confidential information with the sensor terminal. 
     Preferably, a storage device which stores the result of measurement by the second biological sensor is further included. The control device includes at least one of a component which encrypts the confidential information to be transmitted to the sensor terminal with a prescribed result of measurement stored in the storage device and a component which decrypts the confidential information received from the sensor terminal based on the prescribed result of measurement. 
     Further preferably, the prescribed result of measurement includes a most recent result of measurement among the results of measurement by the second biological sensor stored in the storage device. 
     Preferably, the control device transmits the prescribed result of measurement to the sensor terminal through short-range wireless communication. 
     According to another aspect, an information processing terminal is an information processing terminal which transmits a control signal to an external device, and the information processing terminal includes a reception device which receives information from a sensor terminal. The sensor terminal includes a first biological sensor which measures biological information of a first type. The reception device is configured to receive a result of measurement by the first biological sensor from the sensor terminal. The information processing terminal further includes a second biological sensor which measures biological information of the first type and a control device which transmits the control signal to the external device when the result of measurement by the first biological sensor satisfies a predetermined condition for a result of measurement by the second biological sensor. 
     According to yet another aspect, an information processing system including the above-described information processing terminal and a sensor terminal is provided. 
     According to still another aspect, a non-transitory computer readable recording medium having a program for transmitting a control signal to an external device stored thereon is provided. The program causes the computer to perform receiving a result of measurement of biological information of a first type from a sensor terminal, obtaining the result of measurement of the biological information of the first type by a biological sensor connected to the computer, determining whether or not a result of measurement by the biological sensor satisfies a predetermined condition for the result of measurement received from the sensor terminal, and transmitting the control signal to the external device when it is determined that the predetermined condition is satisfied. 
     Preferably, the control device is configured to determine that the result of measurement by the first biological sensor satisfies the predetermined condition when a ratio of match between the results of measurement by the first and second biological sensors within a prescribed period is equal to or higher than a prescribed value. 
     Preferably, an operation acceptance device which accepts input of information is further included. The control device is configured to transmit a request signal requesting measurement of the biological information of the first type by the first biological sensor and transmission of a result of measurement of the biological information to the sensor terminal in response to input of predetermined information to the operation acceptance device. 
     Further preferably, the control device is configured to transmit again the request signal to the sensor terminal up to a prescribed number of times defined as an upper limit when it is determined that the result of measurement by the first biological sensor transmitted in response to transmission of the request signal does not satisfy the predetermined condition. 
     Further preferably, the control device is configured to determine whether or not the result of measurement by the first biological sensor satisfies the predetermined condition by calculating a first average value representing an average value of a plurality of results of measurement by the first biological sensor transmitted in response to transmission of the request signal, calculating a second average value representing an average value of a plurality of results of measurement by the second biological sensor corresponding to the plurality of results of measurement by the first biological sensor, and determining whether or not the first average value satisfies a predetermined condition for the second average value. 
     Further preferably, the control device is configured to correct a result of next measurement by the first biological sensor based on a difference between the first average value and the second average value and to determine whether or not the result of next measurement by the first biological sensor satisfies the predetermined condition when it is determined that the first average value does not satisfy the predetermined condition for the second average value. 
     Preferably, the control device is configured to further transmit to the sensor terminal, a synchronization signal designating timing to conduct measurement with the first biological sensor. The second biological sensor is configured to measure the biological information of the first type at the timing in accordance with the synchronization signal. 
     Preferably, the control device is configured to give an error notification when it is determined that the result of measurement by the first biological sensor does not satisfy the predetermined condition. 
     Preferably, the control device is configured to verify whether or not transmission of the confidential information to the sensor terminal has been successful by comparing the confidential information transmitted to the sensor terminal with at least a part of the confidential information returned from the sensor terminal. 
     Further preferably, a storage device which stores confidential information to be transmitted to the sensor terminal is further included. The control device is configured to erase from the storage device the confidential information transmitted to the sensor terminal when success of transmission of the confidential information to the sensor terminal has been verified. 
     According to yet another aspect, with a control method, an information processing terminal including a biological sensor which measures biological information of a first type communicates confidential information with a sensor terminal which measures biological information of the first type. The control method includes receiving a result of measurement of the biological information of the first type from the sensor terminal, measuring biological information of the first type, determining whether or not the result of measurement received from the sensor terminal satisfies a predetermined condition for a result of measurement of the biological information in the measuring biological information, and communicating confidential information with the sensor terminal when it is determined that the predetermined condition is satisfied. 
     According to yet another aspect, a non-transitory computer readable recording medium having a program stored thereon, the program for causing the computer to perform the control method described above, is provided. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating overview of an operation of an information processing system according to an embodiment. 
         FIG. 2  is a block diagram illustrating a hardware configuration of an information processing terminal according to a first embodiment. 
         FIG. 3  is a diagram representing one example of a specific manner of the information processing terminal according to the first embodiment. 
         FIG. 4  is a sequence diagram illustrating control for transmission of confidential information to another information processing terminal by the information processing terminal according to the first embodiment. 
         FIG. 5  is a flowchart illustrating control of communication of confidential information in the information processing terminal according to the first embodiment. 
         FIG. 6  is a diagram illustrating a table for storing information on communication of the confidential information according to the first embodiment. 
         FIG. 7  is a diagram illustrating comparison of results of measurement by biological sensors according to the first embodiment. 
         FIG. 8  is a functional block diagram illustrating a functional configuration of a control device for performing a series of processes for communicating the confidential information. 
         FIG. 9  is a flowchart illustrating control of communication of the confidential information in the information processing terminal according to the first embodiment. 
         FIG. 10  is a diagram illustrating an exemplary configuration of an information processing system according to a second embodiment. 
         FIG. 11  is a block diagram illustrating an exemplary hardware configuration of an information processing terminal according to the second embodiment. 
         FIG. 12  is a sequence diagram illustrating control for transmission of highly confidential information to another information processing terminal by the information processing terminal according to the second embodiment. 
         FIG. 13  is a sequence diagram illustrating control for transmission of less confidential information to another information processing terminal by the information processing terminal according to the second embodiment. 
         FIG. 14  is a diagram illustrating an exemplary configuration of an information processing system according to a third embodiment. 
         FIG. 15  is a sequence diagram illustrating control for transmission of a control signal to an unmanned aerial vehicle according to the third embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of this invention will be described in detail below with reference to the drawings. The same or corresponding elements in the drawings have the same reference characters allotted and description thereof will not be repeated. 
     A. Overview 
       FIG. 1  is a diagram illustrating overview of an operation of an information processing system  1  according to an embodiment. Referring to  FIG. 1 , information processing system  1  includes an information processing terminal  100 A and an information processing terminal  100 B. Information processing terminals  100 A and  100 B include biological sensors  120 A and  120 B for measuring biological information, respectively. 
     Control for information processing terminal  100 A to communicate confidential information with information processing terminal  100 B will be described below. 
     In step S 1 , a user inputs to information processing terminal  100 A, an instruction for transmitting confidential information to information processing terminal  100 B. 
     In step S 2 , information processing terminal  100 A transmits a signal indicating measurement of biological information with biological sensor  120 B to information processing terminal  100 B in response to the input of the instruction from the user. 
     In step S 3 , information processing terminal  100 B measures biological information of the user with biological sensor  120 B based on the signal input from information processing terminal  100 A and transmits a result of measurement to information processing terminal  100 A. 
     In step S 4 , information processing terminal  100 A measures biological information of the user with biological sensor  120 A. A type of the biological information measured with biological sensor  120 A is the same as a type of the biological information measured with biological sensor  120 B. In steps S 3  and  4 , biological sensors  120 A and  120 B measure biological information of the same user. 
     In step S 5 , information processing terminal  100 A determines whether or not the result of measurement by biological sensor  120 B satisfies a predetermined condition for the result of measurement by biological sensor  120 A (for example, whether or not results of measurement by both of them match with each other). When information processing terminal  100 A determines in step S 5  that the result of measurement by biological sensor  120 B satisfies the condition, information processing terminal  100 A transmits in step S 6  confidential information to information processing terminal  100 B. 
     According to the above, in communication of confidential information, the user should only measure biological information of the user himself/herself with the biological sensor mounted on each information processing terminal which communicates. Therefore, the user does not have to memorize complicated authentication information (a password) nor to take notes of the authentication information. Consequently, the information processing system according to the embodiment is higher in security than a conventional system. 
     The information processing system according to the embodiment performs authentication by using biological information of which copying or obtainment is very difficult for a malicious third party in communication of confidential information. Consequently, the information processing system according to the embodiment can suppress impersonation more than the conventional system. A detailed configuration and control of this information processing system will be described below. 
     B. First Embodiment 
     (b1. Hardware Configuration of Information Processing Terminals  100 A and  100 B) 
       FIG. 2  is a block diagram illustrating a hardware configuration of information processing terminals  100 A and  100 B according to a first embodiment. Referring to  FIG. 2 , information processing terminal  100 A includes, as main constituent elements, an operation acceptance device  110 A, biological sensor  120 A, a notification device  130 A, a storage device  140 A, a real time clock (RTC)  150 A, a communication device  160 A, and a control device  170 A. 
     Operation acceptance device  110 A accepts an operation by a user onto information processing terminal  100 A. For example, operation acceptance device  110 A is implemented by a mouse, a keyboard, a hardware button, a touch panel, or other input devices. 
     Biological sensor  120 A obtains biological information of a user. By way of example, biological sensor  120 A measures pulse waves. The biological information measured by biological sensor  120 A is not limited to pulse waves, and in another aspect, a heart rate, a blood pressure, a temperature, a parasympathetic nerve activity, a sympathetic nerve activity, an amount of activity (an acceleration), an electrocardiogram, body motion, percutaneous arterial blood oxygen saturation (SpO2), or a pulse wave transit time may be measured. Preferably, the biological information measured with biological sensor  120 A is information which varies over time because it would be more difficult for a malicious third party to obtain such biological information. 
     Notification device  130 A is a component which notifies a user of information and it is implemented by a display by way of example. In another aspect, notification device  130 A may be a component which notifies a user of information through vibration by a vibrator or sound from a speaker. 
     Storage device  140 A stores setting of information processing terminal  100 A and a result of measurement by biological sensor  120 A. RTC  150 A is a component which counts time and continues to count time with an embedded battery even when power supply to information processing terminal  100 A is stopped. 
     Communication device  160 A is configured to be able to communicate with information processing terminal  100 B through wireless communication. By way of example, communication device  160 A communicates with information processing terminal  100 B under the near field communication (NFC) standard. In another aspect, communication device  160 A may communicate under such a wireless communication scheme as an infrared scheme, the Bluetooth® standard, the wireless fidelity (WiFi) standard, and a scheme using electromagnetic induction such as a contactless integrated circuit (IC) card. Preferably, communication device  160 A desirably communicates under the short-range wireless communication standard relatively small (for example, 1 meter to several centimeters) in coverage. Impersonation by a malicious third party can thus be suppressed. 
     Control device  170 A is responsible for overall operations of information processing terminal  100 A. Control device  170 A is implemented, for example, by at least one integrated circuit. The integrated circuit is implemented, for example, as at least one central processing unit (CPU), at least one application specific integrated circuit (ASIC), at least one field programmable gate array (FPGA), or combination thereof. 
     Since information processing terminals  100 A and  100 B are identical to each other in basic configuration, description of information processing terminal  100 B will not be repeated. In another aspect, information processing terminal  100 B may be configured differently from information processing terminal  100 A and it should only be configured to include at least biological sensor  120 B and communication device  160 B. In other words, in one aspect, information processing terminal  100 B functions as a sensor terminal which measures biological information (pulse waves) of a user with biological sensor  120 B and transmits a result of measurement to information processing terminal  100 A. Control for information processing terminal  100 A to communicate confidential information with information processing terminal  100 B will be described below with reference to  FIGS. 3 and 4 . 
     (b2. Control for Communicating Confidential Information) 
       FIG. 3  is a diagram representing one example of a specific manner of information processing terminals  100 A and  100 B according to the first embodiment. As shown in  FIG. 3 , information processing terminals  100 A and  100 B are wearable terminals of a wrist band type configured to be attachable to a user. In another aspect, information processing terminals  100 A and  100 B may each be a mobile computer, a tablet computer, a mobile device (for example, a smartphone or a PDA), a desktop computer, or any other devices having appropriate processing capability, communication capability, and a memory. 
     In  FIG. 3 , operation acceptance devices  110 A and  110 B are implemented by at least one hardware button. Biological sensors  120 A and  120 B measure pulse waves with a light reflective sensor arranged on an inner circumferential surface of a wrist band type terminal by way of example. 
       FIG. 4  is a sequence diagram illustrating control for transmission by information processing terminal  100 A of confidential information to  100 B according to the first embodiment. In  FIG. 4 , a user transmits confidential information stored in storage device  140 A of information processing terminal  100 A to information processing terminal  100 B. An exemplary condition may be such that a state of charge of a battery (not shown) which drives information processing terminal  100 A is low and a result of measurement in information processing terminal  100 A is desirably taken over by another information processing terminal  100 B in using information processing terminal  100 B. Another exemplary condition may be such that information processing terminal  100 B is a successor model of information processing terminal  100 A and a result of measurement in information processing terminal  100 A is desirably transferred thereto. Other examples of information stored in storage device  140 A include such information as password data, a social security and tax number (my number), an employee number, and information on a server which one is authorized to access. 
     In sequence sq 10 , a user inputs to operation acceptance device  110 A of information processing terminal  100 A, an operation defined in advance for transmitting information stored in storage device  140 A to information processing terminal  100 B. 
     In sequence sq 12 , information processing terminal  100 A determines whether or not a security level of confidential information designated by the user is equal to or higher than a predetermined level. Details of this processing will be described later. In the example shown in  FIG. 4 , information processing terminal  100 A determines the security level of the confidential information designated by the user as the predetermined level or higher. 
     In sequence sq 14 , information processing terminal  100 A transmits a vital data authentication request notification to information processing terminal  100 B. 
     In sequence sq 16 , information processing terminal  100 B returns an acknowledgement (ACK) signal notifying that the vital data authentication request notification has been received to information processing terminal  100 A. 
     In sequence sq 18 , information processing terminal  100 B starts preparation for measurement of biological information (pulse waves) by biological sensor  120 B. 
     In sequence sq 20 , information processing terminal  100 A transmits a synchronization signal to information processing terminal  100 B in response to reception of the ACK signal from information processing terminal  100 B. The synchronization signal synchronizes timing of measurement of biological information (pulse waves) by biological sensors  120 A and  120 B. By way of example, information processing terminal  100 A generates a synchronization signal including time to start measurement, an interval between measurements, and the number of times of measurement by referring to time counted by RTC  150 A. In another aspect, information processing terminal  100 A may be configured to transmit a synchronization signal including the current time counted by RTC  150 A in order to synchronize the current time between RTC  150 A and RTC  150 B. The interval between measurements and the number of times of measurement included in the synchronization signal are defined in a table Ta 1  which will be described later. 
     In sequence sq 22 , information processing terminal  100 B starts measurement of pulse waves of the user in response to the synchronization signal input from information processing terminal  100 A. In sequence sq 24 , information processing terminal  100 A also starts measurement of pulse waves of the user in response to the synchronization signal transmitted to information processing terminal  100 B. 
     In sequence sq 26 , information processing terminal  100 A quits measurement of pulse waves. In sequence sq 28 , information processing terminal  100 A transmits a request signal requesting transmission of a result of measurement by biological sensor  120 B to information processing terminal  100 B. In sequence sq 30 , information processing terminal  100 A stores (saves) a result of measurement by biological sensor  120 A in storage device  140 A. 
     In sequence sq 32 , information processing terminal  100 B transmits the result of measurement by biological sensor  120 B to information processing terminal  100 A in response to an input of the request signal from information processing terminal  100 A. 
     In sequence sq 34 , information processing terminal  100 A determines whether or not the result of measurement by biological sensor  120 A satisfies a predetermined condition for the result of measurement by biological sensor  120 B. Details of this determination method will be described later. 
     In sequence sq 36 , information processing terminal  100 A transmits a result of determination in sequence sq 34  that the predetermined condition has been satisfied to information processing terminal  100 B. 
     In sequence sq 38 , information processing terminal  100 B returns the ACK signal notifying that the result of determination has been received to information processing terminal  100 A and starts preparation for reception of data from information processing terminal  100 A. 
     In sequence sq 40 , information processing terminal  100 A transmits the confidential information stored in storage device  140 A through communication device  160 A to information processing terminal  100 B in response to reception of the ACK signal from information processing terminal  100 B. In another aspect, information processing terminals  100 A and  100 B may be configured to include another communication interface higher in bit rate than communication devices  160 A and  160 B separately from communication devices  160 A and  160 B. In such a configuration, information processing terminal  100 A may be configured to use another communication interface for transmission of the confidential information in sequence sq 40 . Examples of other communication interfaces include the Bluetooth® standard. According to such a configuration, information processing terminals  100 A and  100 B can efficiently transmit and receive information in accordance with a communication scheme small in coverage such as the NFC standard in order to prevent impersonation until mutual authentication is achieved, and in accordance with a communication scheme higher in bit rate after authentication. 
     In sequence sq 42 , information processing terminal  100 B saves the confidential information received from information processing terminal  100 A in storage device  140 B. In sequence sq 44 , information processing terminal  100 B returns at least a part of the information received from information processing terminal  100 A to information processing terminal  100 A as confirmation data. In another aspect, information processing terminal  100 B may be configured to return a cyclic redundancy check (CRC) signal on information received from information processing terminal  100 A to information processing terminal  100 A. 
     In sequence sq 46 , information processing terminal  100 A verifies whether or not the confirmation data returned from information processing terminal  100 B and the information transmitted to information processing terminal  100 B match with each other. In sequence sq 48 , when information processing terminal  100 A verifies match between the confirmation data returned from information processing terminal  100 B and the information transmitted to information processing terminal  100 B, it transmits a notification of success which notifies information processing terminal  100 B of success of backup to information processing terminal  100 B. 
     In sequence sq 50 , information processing terminal  100 A erases (formats) the confidential information stored in storage device  140 A, which has been transmitted to information processing terminal  100 B, in response to success of verification. Thus, information processing system  1  can erase information which is stored in information processing terminal  100 A and may no longer be used by the user so that security can be ensured. 
     In sequence sq 52 , information processing terminal  100 A shows on notification device  130 A that a series of data transfer processes including erasure of information stored in storage device  140 A has ended. 
     The series of sequences does not necessarily have to be performed in the order shown in  FIG. 4 . For example, sequence sq 16  and sequence sq 18  may be interchanged. In another aspect, confidential information stored in information processing terminal  100 A may desirably be backed up (copied) in information processing terminal  100 B. In such a case, information processing terminal  100 A may be configured not to perform sequence sq 50 . Processing in each of information processing terminals  100 A and  100 B in the series of authentication processes will now be described. 
     (b3. Processing in Information Processing Terminal  100 A) 
       FIG. 5  is a flowchart illustrating control of communication of confidential information in information processing terminal  100 A according to the first embodiment. Processing shown in  FIG. 5  is performed by execution of a control program stored in storage device  140 A by control device  170 A. In another aspect, processing may be performed in part or in its entirety by a circuit element or other hardware. 
     In step S 100 , control device  170 A determines whether or not a data transmission request event has occurred. More specifically, control device  170 A makes determination based on contents input to operation acceptance device  110 A. 
     When control device  170 A determines that the data transmission request event from a user has occurred (YES in step S 100 ), the process proceeds to step S 102 . Otherwise (NO in step S 100 ), the process returns to step S 100  and control device  170 A waits for occurrence of a data transmission request event. 
     In step S 102 , control device  170 A determines whether or not data of interest in the data transmission request event requires comparison and determination based on biological information (vital data) (hereinafter also referred to as “highly confidential information”). More specifically, control device  170 A makes such determination based on a security level of the data of interest. 
     The highly confidential information is information of which leakage to the outside is serious, and examples thereof include password data, a social security and tax number (my number), an employee number, information on a server which one is authorized to access, and biological information (a result of measurement by biological sensor  120 A). 
     Control device  170 A determines a security level of data of interest based on a storage area where the data of interest is stored (whether or not data is saved in a specific folder) or security information added to the data of interest. A user can set a security level of confidential information stored in storage device  140 A and including the data of interest by operating operation acceptance device  110 A. After control device  170 A determines the security level of data of interest, it determines whether or not the data of interest is highly confidential information requiring comparison and determination based on biological information by referring to table Ta 1  shown in  FIG. 6 . 
       FIG. 6  is a diagram illustrating table Ta 1  for storing information on communication of the confidential information according to the first embodiment. Table Ta 1  includes a method of transmitting confidential information, the number of terminals to which confidential information is simultaneously transmitted, identification information of a terminal to which confidential information is transmitted, setting information for measurement of biological information (vital data), and information on a method of comparison and determination of biological information, and the table is stored in storage device  140 A. 
     The method of transmitting confidential information is set for each security level. In the example shown in  FIG. 6 , control device  170 A is set to transmit confidential information “high” in security level after comparison based on biological information and to transmit confidential information “medium” and “low” in security level without comparison based on biological information. Confidential information not requiring comparison and determination based on biological information will hereinafter also be referred to as “less confidential information.” 
     In another aspect, information shown in  FIG. 6  may be present as an independent table. In the example shown in  FIG. 6 , a value in &lt;&gt; is configured to be variable through an operation of operation acceptance device  110 A by a user/a manager. In one aspect, information processing terminal  100 A has a determination method according to conventional secure simple pairing (SSP) other than the determination method based on comparison of biological information as a method of transmitting confidential information, and it may be configured to allow a user to select any determination method. 
     In another aspect, control device  170 A may be configured to ask a user about a security level of data of interest or whether or not comparison and determination based on biological information is required through notification device  130 A in response to occurrence of a transmission request event. According to such a configuration, a user responds to contents of an inquiry shown on notification device  130 A through operation acceptance device  110 A. 
     When control device  170 A determines that the data of interest is highly confidential information (YES in step S 102 ), the process proceeds to step S 104 . Otherwise (NO in step S 102 ), control device  170 A transmits the data of interest to information processing terminal  100 B without making determination based on comparison of the biological information (step S 130 ). 
     In step S 104 , control device  170 A transmits a vital data authentication request notification to information processing terminal  100 B. The vital data authentication request notification substantially functions as a signal requesting from information processing terminal  100 B, measurement of the biological information (pulse waves) of a user with biological sensor  120 B. 
     In another aspect, control device  170 A may be configured to transmit information on a security level of the data of interest to information processing terminal  100 B instead of the vital data authentication request notification. In such a case, information processing terminal  100 B also has information at least on a method of transmitting confidential information in table Ta 1 . Information processing terminal  100 B determines whether or not biological information should be measured with biological sensor  120 B based on the received information on the security level, and when it determines that measurement is required, it prepares for measurement. 
     In step S 106 , control device  170 A generates a synchronization signal by referring to table Ta 1  in response to reception of the ACK signal from information processing terminal  100 B and transmits the synchronization signal to information processing terminal  100 B. In the example shown in  FIG. 6 , control device  170 A transmits a synchronization signal including time to start measurement and an indication that measurement be conducted at a 6-second interval 10 times in total to information processing terminal  100 B. 
     In step S 107 , control device  170 A has biological sensor  120 A measure biological information (pulse waves) under a condition the same as defined in the synchronization signal transmitted to information processing terminal  100 B. 
     In step S 108 , control device  170 A determines whether or not measurement of the biological information with biological sensor  120 A has ended. In the example shown in  FIG. 6 , control device  170 A determines that measurement of the biological information has ended at the time point when biological sensor  120 A obtains ten results of measurement in total. 
     When control device  170 A determines that measurement of the biological information with biological sensor  120 A has ended (YES in step S 108 ), the process proceeds to step S 110 . Otherwise (NO in step S 108 ), the process returns to step S 107 . 
     In step S 110 , control device  170 A transmits a request signal requesting a result of measurement by biological sensor  120 B to information processing terminal  100 B. Thereafter, information processing terminal  100 A receives the result of measurement by biological sensor  120 B transmitted from information processing terminal  100 B. 
     In step S 112 , control device  170 A determines whether or not reception of the result of measurement by biological sensor  120 B from information processing terminal  100 B has been completed. When control device  170 A determines that reception has been completed (YES in step S 112 ), the process proceeds to step S 114 . Otherwise (NO in step S 112 ), control device  170 A stands by until reception of the result of measurement by biological sensor  120 B is completed. 
     In another aspect, control device  170 A may be configured such that when it cannot receive the result of measurement from information processing terminal  100 B after lapse of a prescribed time period since transmission of the request signal requesting a result of measurement by biological sensor  120 B, it transmits a request signal again or gives an error notification to notification device  130 A. 
     In step S 114 , control device  170 A determines whether or not the result of measurement by biological sensor  120 B received from information processing terminal  100 B satisfies a predetermined condition for the result of measurement by biological sensor  120 A. More specifically, control device  170 A determines whether or not corresponding results of measurement by biological sensors  120 A and  120 B match with each other under criteria shown in table Ta 1  shown in  FIG. 6 . 
       FIG. 7  is a diagram illustrating comparison of results of measurement by biological sensors  120 A and  120 B according to the first embodiment. In the example above, biological sensors  120 A and  120 B measure pulse waves of a user. In the example in  FIG. 7 , outputs from biological sensors  120 A and  120 B indicate voltages representing a ratio of reflected light to incident light. 
     Biological sensors  120 A and  120 B start measurement of pulse waves from time T 0  in response to a synchronization signal and measure pulse waves at 10 time points in total of time points T 1 , T 2 , T 3 , . . . , and T 9  every six seconds. 
     Control device  170 A compares each result of measurement by biological sensor  120 A with each corresponding result of measurement by biological sensor  120 B in a determination example shown in  FIG. 6 . When a difference between a measurement value from biological sensor  120 A and a corresponding measurement value from biological sensor  120 B is within 5%, control device  170 A determines that these results of measurement match with each other. For example, when a difference between the measurement value from biological sensor  120 A and the measurement value from  120 B at time T 1  is 3% of the measurement value from biological sensor  120 A, control device  170 A determines that the corresponding results of measurement at time T 1  match with each other. 
     Referring again to  FIG. 5 , in step S 116 , control device  170 A determines whether or not results of measurement by biological sensors  120 A and  120 B match with each other. In the example shown in  FIG. 6 , when there are seven or more results of measurement indicating match among ten corresponding results of measurement from biological sensors  120 A and  120 B, control device  170 A determines that the result of measurement by biological sensor  120 B satisfies a predetermined condition for the result of measurement by biological sensor  120 A, that is, results of measurement by biological sensors  120 A and  120 B match with each other. 
     When control device  170 A determines that the results of measurement by biological sensors  120 A and  120 B match with each other (YES in step S 116 ), the process proceeds to step S 118 . Otherwise (NO in step S 116 ), the process proceeds to step S 120 . 
     In step S 118 , control device  170 A transmits a vital data match notification indicating match between the results of measurement by biological sensors  120 A and  120 B to information processing terminal  100 B. Thereafter, in step S 130 , control device  170 A allows transmission of confidential information to information processing terminal  100 B. 
     In step S 120 , control device  170 A determines whether or not the results of measurement by biological sensors  120 A and  120 B fail to match with each other. In the example shown in  FIG. 6 , control device  170 A determines that the results of measurement by biological sensors  120 A and  120 B fail to match with each other when there are less than three results of measurement indicating match among ten corresponding results of measurement by biological sensors  120 A and  120 B. 
     When control device  170 A determines that the results of measurement by biological sensors  120 A and  120 B fail to match with each other (YES in step S 120 ), the process proceeds to step S 122 . Otherwise (NO in step S 120 ), the process proceeds to step S 124 . 
     In step S 122 , control device  170 A notifies notification device  130 A of an error indicating unmatch between the results of measurement by biological sensors  120 A and  120 B. 
     In step S 124 , processing for remeasuring biological information is performed. In step S 126 , control device  170 A transmits a signal requesting measurement of biological information of the user with biological sensor  120 B to information processing terminal  100 B. In the example shown in  FIG. 6 , when there are three or more and less than seven results of measurement indicating match among ten corresponding results of measurement by biological sensors  120 A and  120 B, control device  170 A newly measures biological information and determines again match/unmatch of new biological information. 
     Though control device  170 A performs processing such that the process proceeds from step S 120  to step S 124  in the example above, limitation thereto is not intended. In another aspect, as shown in  FIG. 6 , control device  170 A may set the upper limit of the number of times of remeasurement of biological information. In such a case, control device  170 A may be configured to count the number of times of remeasurement before transition from step S 120  to step S 124  and to perform processing in step S 122  when it is determined that the number of counts exceeds a prescribed number of times (three times in the example in  FIG. 6 ). 
     In another aspect, control device  170 A may be configured otherwise, rather than being configured to determine whether or not a ratio of match between results of measurement by biological sensors  120 A and  120 B within a prescribed period is equal to or higher than a prescribed value as above in determination of match/unmatch between the results of measurement. The configuration may be, for example, such that whether or not a similarity calculated from amplitude, a period, or timing of an inflection point between the results of measurement by biological sensors  120 A and  120 B is equal to or higher than a prescribed value is determined. 
     Though information processing terminal  100 A which transmits confidential information is configured to determine match/unmatch of biological information in the example above, limitation thereto is not intended. In another aspect, information processing terminal  100 B which receives confidential information may be configured to determine match/unmatch of biological information and to transmit a result of determination to information processing terminal  100 A. According to such a configuration, information processing terminal  100 A may be configured to transmit confidential information to information processing terminal  100 B upon receiving a result of determination indicating match of biological information. 
     Correction of data for determining match/unmatch between results of measurement by biological sensors  120 A and  120 B will now be described. 
     Results of measurement by biological sensors  120 A and  120 B may be varied depending on proximity between a sensor and a user. Therefore, in one aspect, control device  170 A determines match/unmatch by comparing an average value of results of measurement by biological sensor  120 A (hereinafter also referred to as a “first average value”) with an average value of results of measurement by biological sensor  120 B (hereinafter also referred to as a “second average value”) when results of measurement do not match with each other (NO in step S 116 ). 
     For example, when match/unmatch between results of measurement is determined for a second time, control device  170 A determines whether or not an average value of results of corresponding first and second measurements by biological sensor  120 A matches with an average value of results of corresponding first and second measurements by biological sensor  120 B. The criteria are the same as in determination for the first time. 
     According to the above, even when results of measurement are varied due to some factor, control device  170 A can determine match/unmatch between average values with variation being suppressed each time of remeasurement. 
     In another aspect, control device  170 A may be configured to perform offset correction based on a difference between the first average value and the second average value when results of measurement do not match with each other (NO in step S 116 ). For example, when match/unmatch between results of measurement is determined for a third time, control device  170 A calculates the first average value and the second average value based on results of first to third measurements and calculates a difference value obtained by subtracting the first average value from the second average value. Then, control device  170 A performs correction for adding the difference value to the result of third measurement by biological sensor  120 A. Control device  170 A determines match/unmatch by comparing the corrected result of measurement by biological sensor  120 A with the result of third measurement by biological sensor  120 B. 
     According to the above, control device  170 A can determine match/unmatch between results of measurement by biological sensors  120 A and  120 B with a manufacturing error and a measurement error resulting from proximity between a sensor and a user being suppressed. 
     A result of measurement of biological information may be different depending on a measurement site. For example, a blood pressure is measured as being higher than a true value when a measurement site is located at a position lower than the heart. Therefore, in yet another aspect, control device  170 A may be configured such that when results of measurement fail to match with each other (YES in step S 120 ), the control device has notification device  130 A show an instruction to interchange positions of attachment of information processing terminals  100 A and  100 B. In this configuration as well, control device  170 A uses average values of a result of measurement before interchanging the positions of measurement and a result of measurement after interchange in determination again of match/unmatch between results of measurement. In other words, control device  170 A makes determination by using average values of results of measurement before and after an instruction to interchange positions of attachment of information processing terminals  100 A and  100 B is shown on notification device  130 A. 
     According to the above, control device  170 A can determine match/unmatch based on average values of results of measurement, with influence by a measurement site being suppressed. 
     (b4. Functional Configuration of Control Device  170 A) 
       FIG. 8  is a functional block diagram illustrating a functional configuration of control device  170 A for performing a series of processes for communicating confidential information. Referring to  FIG. 8 , control device  170 A includes, as main functional components relating to processing for communicating confidential information, an input acceptance unit  210 , a security level determination unit  211 , a request unit  212 , a synchronization signal generator  214 , a measurement conducting unit  216 , a biological information acceptance unit  220 , a counter  222 , an average calculator  224 , a determination unit  226 , a notification unit  230 , a data transmitter  240 , a checking unit  242 , and an eraser  244 . 
     Input acceptance unit  210  accepts a data transmission request from a user through operation acceptance device  110 A. Input acceptance unit  210  transmits a signal giving a notification of occurrence of a data transmission request event to security level determination unit  211 . 
     Security level determination unit  211  accesses storage device  140 A and determines a security level of data of interest. Then, security level determination unit  211  verifies whether or not the determined security level requires comparison and determination of biological information by referring to table Ta 1 . 
     When security level determination unit  211  determines that the data of interest is less confidential information, it transmits a signal notifying data transmitter  240  of that determination. Data transmitter  240  accesses storage device  140 A and transmits data of interest to information processing terminal  100 B in response to reception of the signal from security level determination unit  211 . 
     When security level determination unit  211  determines that the data of interest is highly confidential information, it transmits a signal notifying request unit  212  and synchronization signal generator  214  of that determination. 
     Synchronization signal generator  214  generates a synchronization signal based on time counted by RTC  150 A and the number of times of measurement and a measurement interval stored in table Ta 1  and outputs the synchronization signal to request unit  212  and measurement conducting unit  216 . 
     Request unit  212  transmits a synchronization signal  312  input from synchronization signal generator  214  and a request signal  314  requesting a result of measurement by biological sensor  120 B at the timing in accordance with synchronization signal  312  to information processing terminal  100 B at appropriate timing. 
     Measurement conducting unit  216  has biological sensor  120 A measure biological information based on synchronization signal  312  input from synchronization signal generator  214 . 
     Biological information acceptance unit  220  accepts inputs of a result of measurement by biological sensor  120 A (hereinafter also referred to as a “first result of measurement”) and a result of measurement by biological sensor  120 B (hereinafter also referred to as a “second result of measurement”) and outputs such information to average calculator  224 . Biological information acceptance unit  220  transmits a signal to counter  222  each time it accepts an input of the first result of measurement or the second result of measurement in a series of data transmission processes. 
     Counter  222  counts up a value stored in a count up circuit each time it receives an input of a signal from biological information acceptance unit  220  in the series of data transmission processes. 
     Average calculator  224  calculates a first average value representing an average value of first results of measurement and a second average value representing an average value of second results of measurement. More specifically, average calculator  224  recognizes how many times each biological sensor conducted measurement of biological information in the series of data transmission processes by referring to counter  222 . Average calculator  224  calculates the first and second average values by dividing accumulated values of the first and second results of measurement in the series of data transmission processes by the number of times. Average calculator  224  outputs the calculated first and second average values to determination unit  226 . 
     Determination unit  226  determines whether or not the first average value and the second average value match with each other based on criteria stored in table Ta 1  by referring to storage device  140 A. When determination unit  226  determines that the first average value and the second average value match with each other, it outputs that determination to counter  222 , notification unit  230 , and data transmitter  240 . Counter  222  initializes a value stored in the count up circuit in response to an input from determination unit  226 . 
     Data transmitter  240  transmits confidential information  340  stored in storage device  140 A to information processing terminal  100 B in response to an input from determination unit  226 . Checking unit  242  receives input of confirmation data  342  from information processing terminal  100 B. Checking unit  242  verifies whether or not transmission of confidential information  340  to information processing terminal  100 B has been successful based on confirmation data  342  and confidential information  340  transmitted to information processing terminal  100 B. Checking unit  242  outputs to eraser  244 , a signal giving a notification of success of transmission of confidential information  340  to information processing terminal  100 B. Eraser  244  erases confidential information  340  stored in storage device  140 A in response to an input from checking unit  242 . 
     When determination unit  226  determines that the first average value and the second average value do not match with each other, it outputs that determination to notification unit  230 . Notification unit  230  receives an input of a signal indicating that the first average value and the second average value do not match with each other from determination unit  226 , reads an error image stored in storage device  140 A, and has notification device  130 A show the image. A user can thus recognize that information processing terminal  100 A has failed in authentication of a terminal which is a transmission destination of confidential information. 
     When determination unit  226  determines that the first average value and the second average value neither match nor unmatch with each other, it determines whether or not measurement of biological information by the biological sensors has been conducted a predetermined number of times (for example, three times) or less in a series of authentication processes by referring to counter  222 . 
     When determination unit  226  determines that measurement of biological information by the biological sensors has been conducted a predetermined number of times or less, it outputs that determination to request unit  212 . Request unit  212  requests generation of a synchronization signal from synchronization signal generator  214  in response to the input from determination unit  226 . Request unit  212  transmits synchronization signal  312  input from synchronization signal generator  214  and request signal  314  to information processing terminal  100 B at appropriate timing. 
     When determination unit  226  determines that the number of times of measurement of biological information by the biological sensors exceeds the predetermined number of times, it outputs that determination to notification unit  230 . Notification unit  230  reads an error image stored in storage device  140 A and has notification device  130 A show the image in response to the input from determination unit  226 . Processing in information processing terminal  100 B in the series of authentication processes will now be described. 
     (b5. Processing in Information Processing Terminal  100 B) 
       FIG. 9  is a flowchart illustrating control of communication of confidential information in information processing terminal  100 B according to the first embodiment. Processing shown in  FIG. 9  is performed by execution of a control program stored in storage device  140 B by control device  170 B. In another aspect, processing may be performed in part or in its entirety by a circuit element or other hardware. 
     In step S 200 , control device  170 B determines whether or not it has received a vital data authentication request notification from information processing terminal  100 A. When control device  170 B determines that it has received the vital data authentication request notification from information processing terminal  100 A (YES in step S 200 ), the process proceeds to step S 202 . Otherwise (NO in step S 200 ), control device  170 B waits for reception of a vital data authentication request notification. 
     In step S 202 , control device  170 B starts preparation for measurement of biological information (vital data) with biological sensor  120 B. 
     In step S 204 , control device  170 B determines whether or not it has received a synchronization signal from information processing terminal  100 A. When control device  170 B determines that it has received a synchronization signal from information processing terminal  100 A (YES in step S 204 ), the process proceeds to step S 206 . Otherwise (NO in step S 204 ), control device  170 B waits for reception of a synchronization signal. 
     In step S 206 , control device  170 B has biological sensor  120 B measure biological information (pulse waves) in response to the input synchronization signal. In step S 208 , control device  170 B determines whether or not measurement by biological sensor  120 B has been conducted a prescribed number of times defined in the synchronization signal. When control device  170 B determines that a prescribed number of times of measurement have been completed (YES in step S 208 ), the process proceeds to step S 210 . Otherwise (NO in step S 208 ), control device  170 B stands by until a prescribed number of times of measurement are completed. 
     In step S 210 , control device  170 B determines whether or not it has received a request signal from information processing terminal  100 A. When control device  170 B determines that it has received a request signal from information processing terminal  100 A (YES in step S 210 ), the process proceeds to step S 212 . Otherwise (NO in step S 210 ), control device  170 B waits for reception of a request signal. 
     In step S 212 , control device  170 B transmits a result of measurement by biological sensor  120 B to information processing terminal  100 A. In step S 214 , control device  170 B determines whether or not transmission of the result of measurement to information processing terminal  100 A has been completed. When control device  170 B determines that transmission of the result of measurement has been completed (YES in step S 214 ), the process proceeds to step S 216 . Otherwise (NO in step S 214 ), control device  170 B stands by until transmission of the result of measurement is completed. 
     In step S 216 , control device  170 B determines whether or not it has received a vital data match notification indicating match between results of measurement by biological sensors  120 A and  120 B from information processing terminal  100 A. When control device  170 B determines that it has received the vital data match notification from information processing terminal  100 A (YES in step S 216 ), it performs reception processing for receiving confidential information from information processing terminal  100 A (step S 218 ). Otherwise (NO in step S 216 ), the process proceeds to step S 220 . 
     In step S 220 , control device  170 B determines whether or not it has received a request signal (a vital data remeasurement notification) requesting remeasurement by biological sensor  120 B from information processing terminal  100 A. When control device  170 B determines that it has received the vital data remeasurement notification (YES in step S 220 ), the process proceeds to step S 222 . Otherwise (NO in step S 220 ), the process proceeds to step S 224 . 
     In step S 222 , control device  170 B prepares for remeasurement of biological information by biological sensor  120 B and waits for reception of a synchronization signal giving a notification of measurement timing. 
     In step S 224 , control device  170 B determines whether or not it has received an error notification indicating unmatch between results of measurement by biological sensors  120 A and  120 B from information processing terminal  100 A. When control device  170 B determines that it has received an error notification from information processing terminal  100 A (YES in step S 224 ), the process proceeds to step S 226 . Otherwise (NO in step S 224 ), the process returns to step S 216 . 
     In step S 226 , control device  170 B has notification device  130 B show an image giving a notification of failure in authentication of information processing terminal  100 A. 
     (b6. Summary) 
     According to the above, a user should only measure biological information of the user himself/herself with a biological sensor mounted on each information processing terminal which communicates, in communication of confidential information. Therefore, the user does not have to memorize complicated authentication information (a password) nor to take notes of the authentication information. Consequently, information processing system  1  according to the embodiment is higher in security than the conventional system. 
     The information processing system according to the embodiment uses biological information of which copying and obtainment is very difficult for a malicious third party in communication of confidential information. Consequently, the information processing system according to the embodiment can suppress impersonation more than the conventional system. 
     C. Second Embodiment 
     (c1. System Configuration) 
       FIG. 10  is a diagram illustrating an exemplary configuration of an information processing system  2  according to a second embodiment. Information processing terminals  100 A and  100 B according to the first embodiment are both wearable terminals. In the example shown in  FIG. 10 , an information processing terminal  100 B 2  included in information processing system  2  according to the second embodiment is a stationary information processing terminal. 
     Referring to  FIG. 10 , information processing system  2  has information processing terminal  100 A, information processing terminal  100 B 2 , and a server  300  representing an external device. Information processing terminal  100 B 2  and server  300  are configured to be able to communicate with each other. 
     (c2. Configuration of Information Processing Terminal  100 B 2 ) 
       FIG. 11  is a block diagram illustrating an exemplary hardware configuration of information processing terminal  100 B 2  according to the second embodiment. Referring to  FIG. 11 , information processing terminal  100 B 2  is different from information processing terminal  100 B described with reference to  FIG. 2  in having a communication interface (I/F)  180 B for communication with server  300 . By way of example, communication interface  180 B is a wireless local area network (LAN) interface. Information processing terminal  100 B 2  communicates with server  300  connected to a LAN or a WAN through communication interface  180 B. 
     In the second embodiment, by way of example, an interface in conformity with the NFC standard is mounted on communication devices  160 A and  160 B. A rate of communication between information processing terminal  100 B 2  and server  300  is higher than a rate of communication between information processing terminals  100 A and  100 B 2 . 
     (c3. Example in Which Comparison of Biological Information is Made) 
       FIG. 12  is a sequence diagram illustrating control (No. 1) for transmission by information processing terminal  100 A of confidential information to  100 B 2  according to the second embodiment. In the example shown in  FIG. 12 , a user transfers data “high” in security level, that is, highly confidential information, from information processing terminal  100 A to information processing terminal  100 B 2 . Since a portion the same as in  FIG. 4  has the same reference numeral allotted, description thereof will not be repeated. 
     In sequence sq 102 , as shown in  FIG. 10 , a user who wears information processing terminal  100 A holds communication device  160 A of information processing terminal  100 A over communication device  160 B of information processing terminal  100 B 2 . More specifically, the user sets a distance between communication devices  160 A and  160 B each incorporating the NFC interface to a prescribed distance (for example, 10 cm) or smaller. Thus, communication devices  160 A and  160 B can communicate with each other. 
     In sequence sq 104 , information processing terminal  100 B 2  receives first log-in data stored in storage device  140 A of information processing terminal  100 A through communication device  160 B. The first log-in data includes, for example, an account name and a password. 
     In sequence sq 106 , whether or not the received first log-in data matches with log-in data stored in storage device  140 B is determined. 
     In sequence sq 108 , information processing terminal  100 B 2  returns a result of authentication to information processing terminal  100 A. In the example shown in  FIG. 12 , information processing terminal  100 B 2  notifies information processing terminal  100 A of success of authentication based on the first log-in data. 
     In sequence sq 110 , information processing terminal  100 A transmits candidates for transmission data to information processing terminal  100 B 2  in response to reception of a notification of success of authentication. 
     In sequence sq 112 , information processing terminal  100 B 2  shows on notification device  130 B, the candidates for transmission data received from information processing terminal  100 A and accepts selection by a user. The user selects data to be transferred from information processing terminal  100 A to information processing terminal  100 B 2  based on contents shown on notification device  130 B. In the example shown in  FIG. 12 , the user selects highly confidential information. 
     In sequence sq 114 , information processing terminal  100 B 2  transmits a result of selection by the user to information processing terminal  100 A. In sequence sq 12 , information processing terminal  100 A determines a security level of the data selected by the user and determines that the data is highly confidential information. 
     According to the above, confidential information can be communicated also between a wearable terminal and a stationary information processing terminal (for example, a personal computer) while impersonation by a third party is suppressed. 
     In another aspect, sequences sq 110  to  114  do not have to be performed. Information processing terminal  100 A may be configured to transmit predetermined information stored in storage device  140 A to information processing terminal  100 B 2  after a series of comparison and determination processes based on biological information in response to reception of a notification of success of authentication from information processing terminal  100 B 2 . 
     (c4. Example in Which Comparison of Biological Information Is Not Made (No. 1)) 
     Selection of highly confidential information by a user is described in the example shown in  FIG. 12 . Control in an example in which a user selects less confidential information will be described below. 
     Information processing terminal  100 A determines in sequence sq 12  that data selected by a user is less confidential information. Thus, information processing terminal  100 A transmits to information processing terminal  100 B 2  a notification of transmission of less confidential information selected by the user instead of a series of comparison and determination processes based on biological information (sequence sq 14  to sequence sq 36 ). 
     According to the above, information processing system  2  can quickly communicate less confidential information (confidential information of which leakage to the outside does not produce serious damage) without comparison and determination based on biological information. Load imposed on the user can also be mitigated. 
     Though information processing terminal  100 B 2  is configured to store less confidential information received from information processing terminal  100 A in storage device  140 B in the example above, limitation thereto is not intended. In another aspect, information processing terminal  100 B 2  may be configured to transfer less confidential information received from information processing terminal  100 A to server  300  through communication interface  180 B. Information processing terminal  100 B 2  saves information on an area of storage of less confidential information in server  300 , information on connection to server  300 , and authentication information used for logging in server  300  (second log-in data) in storage device  140 B in association with metadata of transmitted less confidential information (for example, a file name). According to such a configuration, information processing terminal  100 B 2  can have server  300  greater in storage capacity than information processing terminal  100 B 2  manage less confidential information of which leakage to the outside does not cause serious influence. 
     Though information processing terminal  100 A is configured to transmit less confidential information as it is to information processing terminal  100 B 2  in the example above, limitation thereto is not intended. Information processing terminal  100 A may be configured to encrypt less confidential information and transmit the encrypted less confidential information to information processing terminal  100 B 2 . By way of example, information processing terminal  100 A encrypts less confidential information with a prescribed result of measurement by biological sensor  120 A. Examples of the prescribed result of measurement include a result of measurement by biological sensor  120 A which is newly obtained each time an event of transmission of less confidential information occurs. Other examples of the prescribed result of measurement include a most recent result of measurement among results of measurement by biological sensor  120 A stored in storage device  140 A. In any case, the prescribed result of measurement is transmitted from information processing terminal  100 A to information processing terminal  100 B 2 . The prescribed result of measurement is communicated through short-range wireless communication between communication devices  160 A and  160 B. Impersonation and interception by a third party can thus be suppressed. 
     (c5. Example in Which Comparison of Biological Information Is Not Made (No. 2)) 
     In the above (example in which comparison of biological information is not made (No. 1)), information processing terminal  100 A and information processing terminal  100 B 2  communicate data in accordance with a communication method under the NFC standard. A rate of data transfer under NFC, however, is approximately from 100 to 400 kbits/s, and when a data of interest has a large size, it takes a long time to transfer the data. While data is transferred, information processing terminal  100 A and information processing terminal  100 B 2  should be kept at a prescribed distance or smaller from each other, and therefore a user cannot move away from information processing terminal  100 B 2  while the user is carrying information processing terminal  100 A. 
     In order to solve the problem, in another aspect, instead of transmission of less confidential information from information processing terminal  100 A to information processing terminal  100 B 2 , server  300  may transmit less confidential information to information processing terminal  100 B 2 . This communication control will be described below. 
       FIG. 13  is a sequence diagram illustrating control for transmission of less confidential information by information processing terminal  100 A to  100 B 2  according to the second embodiment. Since a portion the same as in  FIG. 12  has the same reference numeral allotted, description thereof will not be repeated. 
     In sequence sq 112 A, a user selects less confidential information. In response, in sequence sq 12 , information processing terminal  100 A determines that the data to be transmitted to information processing terminal  100 B 2  is less confidential information. 
     In sequence sq 120 , information processing terminal  100 A checks whether or not the data selected by the user is stored in server  300  configured to be able to communicate with information processing terminal  100 B 2 . By way of example, information processing terminal  100 A determines whether or not the data has been transmitted to server  300  based on tag/flag information (metadata) added to the data selected by the user. When information processing terminal  100 A determines that the data was transmitted to server  300  in the past, it determines that the data is stored in server  300 . In the example shown in  FIG. 13 , information processing terminal  100 A determines that the data selected by the user is stored in server  300 . 
     In sequence sq 122 , information processing terminal  100 A encrypts second log-in data for accessing server  300 . Second log-in data includes, for example, an account name and a password. By way of example, information processing terminal  100 A encrypts the second log-in data with a prescribed result of measurement by biological sensor  120 A stored in storage device  140 A. Specifically, the prescribed result of measurement is a most recent result of measurement (of which time and day of measurement is the latest) among results of measurement by biological sensor  120 A stored in storage device  140 A. More specifically, information processing terminal  100 A calculates peaks from the prescribed result of measurement (for example, the result of measurement shown in  FIG. 7 ) and encrypts the second log-in data with values at three points high in value of the peaks. Server  300  also stores in advance the same encryption condition. 
     In sequence sq 124 , information processing terminal  100 A transmits a transfer instruction for transferring the data selected by the user to information processing terminal  100 B 2  and the encrypted second log-in data to information processing terminal  100 B 2 . In sequence sq 126 , information processing terminal  100 B 2  transfers such information received from information processing terminal  100 A to server  300  through communication interface  180 B. 
     In sequence sq 128 , server  300  specifies a decryption key for decrypting the encrypted second log-in data. By way of example, the user periodically transmits information including the result of measurement by biological sensor  120 A from information processing terminal  100 A to server  300  via information processing terminal  100 B 2 . Under such conditions, server  300  calculates peaks from the most recent result of measurement among results of measurement by biological sensor  120 A stored in the server itself and specifies values at three points high in value of the peaks as a decryption key. 
     In another aspect, information processing terminal  100 A and server  300  may be configured to use a predetermined result of measurement among results of measurement by biological sensor  120 A as an encryption key/a decryption key. 
     In yet another aspect, information processing terminal  100 A may be configured to transmit metadata (for example, time and day of measurement) of a result of measurement by biological sensor  120 A used for encryption together with the encrypted second log-in data. In such a case, server  300  specifies a result of measurement to be used for decryption of the second log-in data with the metadata. 
     In transmission of a result of measurement by biological sensor  120 A to be used for encryption/decryption to information processing terminal  100 B 2 , information processing terminal  100 A desirably transmits the result under the standard of short range wireless communication of which coverage is relatively small (for example, from 1 meter to several centimeters), in order to suppress the possibility of interception of the encryption key/the decryption key by a malicious third party. 
     In sequence sq 130 , server  300  decrypts the encrypted second log-in data based on the specified decryption key. 
     In sequence sq 132 , server  300  determines whether or not the decrypted second log-in data matches with the log-in data stored in the server itself. In the example shown in  FIG. 13 , server  300  determines that the decrypted second log-in data matches with the log-in data stored in the server itself and authenticates information processing terminal  100 B 2 . 
     In sequence sq 134 , server  300  transmits the data selected by the user (less confidential information) to authenticated information processing terminal  100 B 2 . 
     In sequence sq 136 , information processing terminal  100 B 2  saves the data received from server  300  in storage device  140 B. 
     Information processing system  2  according to the configuration can transfer less confidential information to an information processing terminal designated as a destination from server  300  in communication of less confidential information. Consequently, information processing system  2  can transfer less confidential information to the information processing terminal designated as the destination from server  300  at a communication rate higher than a communication rate between information processing terminals  100 A and  100 B. 
     The user who uses information processing system  2  can move away from information processing terminal  100 B 2  (communication device  160 B) with information processing terminal  100 A which does not communicate less confidential information being attached thereto, while information processing terminal  100 B 2  and server  300  are communicating less confidential information therebetween. 
     Information processing terminal  100 A included in information processing system  2  encrypts second log-in data for accessing server  300  with biological information of which copying and obtainment is very difficult for a malicious third party. Therefore, information processing system  2  can suppress impersonation by a malicious third party even in communication of less confidential information. 
     D. Third Embodiment 
     (d1. Overview) 
     Use of an unmanned aerial vehicle such as a drone has recently rapidly spread. Such an unmanned aerial vehicle generally operates in accordance with a predetermined program or by remotely been controlled by an external device. 
     When the external device is impersonated by a malicious third party, the unmanned aerial vehicle is controlled by the third party. For example, when an unmanned aerial vehicle is carrying cargo freights or when an unmanned aerial vehicle is used for the military purpose, people nearby are exposed to jeopardy. 
     A configuration and control for preventing impersonation of an external device which controls an unmanned aerial vehicle will be described below. 
     (d2. System Configuration) 
       FIG. 14  is a diagram illustrating an exemplary configuration of an information processing system  3  according to a third embodiment. Information processing system  3  has an information processing terminal  100 A 3 , information processing terminal  100 B, and an unmanned aerial vehicle  500 . By way of example, information processing terminal  100 A 3  is a tablet terminal. Since information processing terminal  100 A 3  is identical in hardware configuration to information processing terminal  100 B 2  shown in  FIG. 11 , description thereof will not be repeated. 
     Unmanned aerial vehicle  500  is a flying object which performs autonomous operations based on an external control command, and includes a multicopter and a drone by way of example. Information processing terminal  100 A 3  is a terminal for operating unmanned aerial vehicle  500  and an application for controlling operations of unmanned aerial vehicle  500  (hereinafter also referred to as a “control application”) is stored in storage device  140 A. 
     (d3. Method of Controlling Unmanned Aerial Vehicle  500 ) 
     A user of information processing system  3  controls operations of unmanned aerial vehicle  500  by operating information processing terminal  100 A 3  while he/she wears information processing terminal  100 B. 
     Initially, the user launches the control application by operating operation acceptance device  110 A (for example, a touch panel). The control application has notification device  130 A functioning as a display show an operation screen for operating unmanned aerial vehicle  500 . The user operates operation acceptance device  110 A in accordance with a representation on notification device  130 A. 
     The control application verifies whether or not a control signal in accordance with contents input to operation acceptance device  110 A results from impersonation before transmission of the control signal to unmanned aerial vehicle  500 . 
     Specifically, the control application determines whether or not a result of measurement by biological sensor  120 B satisfies a predetermined condition for a result of measurement by biological sensor  120 A (for example, results of measurement from both biological sensors match with each other), and it allows transmission of the control signal to unmanned aerial vehicle  500  only when it determines that the condition is satisfied. Unmanned aerial vehicle  500  operates based on a control signal input from information processing terminal  100 A 3 . Such control will be described below with reference to  FIG. 15 . 
       FIG. 15  is a sequence diagram illustrating control for transmitting a control signal to unmanned aerial vehicle  500  according to the third embodiment. 
     In sequence sq 201 , the user launches the control application by operating operation acceptance device  110 A of information processing terminal  100 A 3  and inputs a control command to unmanned aerial vehicle  500 . 
     In sequence sq 202 , information processing terminal  100 A 3  transmits a vital data authentication request notification to information processing terminal  100 B upon receiving the input of the control command from the user. 
     In sequence sq 203 , information processing terminal  100 B returns an ACK signal giving a notification of reception of the vital data authentication request notification to information processing terminal  100 A 3 . 
     In sequence sq 204 , information processing terminal  100 B starts preparation for measurement of biological information (pulse waves) with biological sensor  120 B. In sequence sq 205 , information processing terminal  100 A 3  transmits a synchronization signal to information processing terminal  100 B in response to reception of the ACK signal from information processing terminal  100 B. 
     In sequence sq 206 , information processing terminal  100 B starts measurement of pulse waves of the user in response to the synchronization signal input from information processing terminal  100 A 3 . In sequence sq 208 , information processing terminal  100 A 3  also starts measurement of pulse waves of the user in response to the synchronization signal transmitted to information processing terminal  100 B. 
     In sequence sq 210 , information processing terminal  100 A 3  quits measurement of the biological information. In sequence sq 212 , information processing terminal  100 A 3  transmits a request signal requesting transmission of the result of measurement by biological sensor  120 B to information processing terminal  100 B. In sequence sq 214 , information processing terminal  100 A 3  stores (saves) the result of measurement by biological sensor  120 A in storage device  140 A. 
     In sequence sq 216 , information processing terminal  100 B transmits the result of measurement by biological sensor  120 B to information processing terminal  100 A 3  in response to an input of the request signal from information processing terminal  100 A 3 . 
     In sequence sq 218 , information processing terminal  100 A 3  determines whether or not the result of measurement by biological sensor  120 A satisfies a predetermined condition for the result of measurement by biological sensor  120 B. By way of example, information processing terminal  100 A 3  determines whether or not the results of measurement by biological sensors  120 A and  120 B match with each other. Determination is based on the condition shown in table Ta 1 . In the example shown in  FIG. 15 , information processing terminal  100 A 3  determines that the results of measurement by biological sensors  120 A and  120 B match with each other. 
     In sequence sq 220 , information processing terminal  100 A 3  transmits a result of determination indicating match between the results of measurement by biological sensors  120 A and  120 B to information processing terminal  100 B. In sequence sq 222 , information processing terminal  100 A 3  transmits a control signal based on the control command from the user to unmanned aerial vehicle  500  through a communication interface  180 A. Communication interface  180 A is a wireless LAN interface by way of example. 
     In sequence sq 224 , unmanned aerial vehicle  500  returns to information processing terminal  100 A 3 , an ACK signal giving a notification of reception of the control signal from information processing terminal  100 A 3 . In sequence sq 226 , unmanned aerial vehicle  500  operates based on the input control signal. 
     According to the above, information processing terminal  100 A 3  according to the third embodiment can determine whether or not a control signal for operating unmanned aerial vehicle  500  has been input by an authorized user by using biological information of which copying and obtainment is very difficult. Therefore, information processing terminal  100 A 3  according to the third embodiment can suppress an operation of unmanned aerial vehicle  500  by an impersonating party. 
     Though information processing terminal  100 A 3  is configured to make comparison and determination based on biological information in response to an input of a control command in the example above, limitation thereto is not intended. In another aspect, information processing terminal  100 A 3  incorporates at least one of an acceleration sensor, a vibration sensor, and a sensor which senses holding of information processing terminal  100 A 3  by a user, which are not shown. Information processing terminal  100 A 3  may be configured to make comparison and determination based on biological information when such a sensor senses a prescribed operation by a user. 
     (d4. Control in Example in Which Results of Measurement Do Not Match) 
     An example in which results of measurement by biological sensors  120 A and  120 B do not match with each other is described with reference to  FIG. 15 . A control example in which these results of measurement do not match with each other will be described below. 
     When it is determined in sequence sq 218  that results of measurement by biological sensors  120 A and  120 B do not match with each other, information processing terminal  100 A 3  determines that the control command has been input by an impersonating third party and transmits an error command to unmanned aerial vehicle  500 . 
     In another aspect, information processing terminal  100 A 3  may be configured to remeasure biological information with biological sensors  120 A and  120 B and compare results of measurement up to a prescribed number of times (for example, three times) defined as the upper limit when it is determined that results of measurement by biological sensors  120 A and  120 B do not match with each other. According to such a configuration, information processing terminal  100 A 3  transmits an error command to unmanned aerial vehicle  500  when it determines a prescribed number of times that the results of measurement by biological sensors  120 A and  120 B do not match with each other. 
     Unmanned aerial vehicle  500  is controlled to perform a predetermined operation in response to reception of an error command. By way of example, unmanned aerial vehicle  500  slowly descends and makes a forced landing while it issues a warning to the surroundings by using sound or light in response to reception of the error command. 
     In another aspect, unmanned aerial vehicle  500  may gain altitude and self-destruct at prescribed timing (for example, timing when the altitude attains to 100 m) in response to reception of the error command. 
     In yet another aspect, unmanned aerial vehicle  500  may locate a wide space where there is no building in the surroundings such as sea and make a forced landing in response to reception of the error command. In this case, unmanned aerial vehicle  500  locates a wide space where there is no building in the surroundings with a camera or a global positioning system (GPS). 
     Unmanned aerial vehicle  500  can minimize influence on people and objects nearby by performing these predetermined operations in response to reception of the error command. 
     Though description has been given above with reference to an unmanned aerial vehicle by way of example, limitation thereto is not intended. Control for suppressing impersonation is applicable to a machine which performs an autonomous operation based on an external control command such as an unmanned vehicle, an unmanned marine vessel, or an exploratory satellite. 
     It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     Additional Aspect 1 
     An information processing terminal which communicates confidential information with a sensor terminal including a first biological sensor which measures biological information of a first type, the information processing terminal including: 
     a reception device which receives a result of measurement by the first biological sensor from the sensor terminal; 
     a second biological sensor which measures biological information of the first type; and 
     a control device configured to communicate the confidential information with the sensor terminal when the result of measurement by the first biological sensor satisfies a predetermined condition for a result of measurement by the second biological sensor. 
     Additional Aspect 2 
     The information processing terminal described in additional aspect 1, in which the control device is configured to determine that the result of measurement by the first biological sensor satisfies the predetermined condition when a ratio of match between the results of measurement by the first and second biological sensors within a prescribed period is equal to or higher than a prescribed value. 
     Additional Aspect 3 
     The information processing terminal described in additional aspect 1 or 2, the information processing terminal further including an operation acceptance device which accepts input of information, in which the control device is configured to transmit to the sensor terminal, a request signal requesting measurement of the biological information of the first type by the first biological sensor and transmission of the result of measurement of the biological information in response to input of predetermined information to the operation acceptance device. 
     Additional Aspect 4 
     The information processing terminal described in additional aspect 3, in which the control device is configured to transmit again the request signal to the sensor terminal up to a prescribed number of times defined as the upper limit when it is determined that the result of measurement by the first biological sensor transmitted in response to transmission of the request signal does not satisfy the predetermined condition. 
     Additional Aspect 5 
     The information processing terminal described in additional aspect 4, in which the control device is configured to calculate a first average value representing an average value of a plurality of results of measurement by the first biological sensor transmitted in response to transmission of the request signal, to calculate a second average value representing an average value of a plurality of results of measurement by the second biological sensor corresponding to the plurality of results of measurement by the first biological sensor, and to determine whether or not the result of measurement by the first biological sensor satisfies the predetermined condition by determining whether or not the first average value satisfies the predetermined condition for the second average value. 
     Additional Aspect 6 
     The information processing terminal described in additional aspect 5, in which the control device is configured to correct a result of next measurement by the first biological sensor based on a difference between the first average value and the second average value and to determine whether or not the result of next measurement by the first biological sensor satisfies the predetermined condition when it is determined that the first average value does not satisfy the predetermined condition for the second average value. 
     Additional Aspect 7 
     The information processing terminal described in any of additional aspects 1 to 6, in which the control device is configured to further transmit a synchronization signal designating timing of measurement by the first biological sensor to the sensor terminal, and the second biological sensor is configured to measure the biological information of the first type at timing in accordance with the synchronization signal. 
     Additional Aspect 8 
     The information processing terminal described in any of additional aspects 1 to 7, in which the control device is configured to give an error notification when it is determined that the result of measurement by the first biological sensor does not satisfy the predetermined condition. 
     Additional Aspect 9 
     The information processing terminal described in any of additional aspects 1 to 8, in which the control device is configured to verify whether or not transmission of the confidential information to the sensor terminal has been successful by comparing the confidential information transmitted to the sensor terminal with at least a part of the confidential information returned from the sensor terminal. 
     Additional Aspect 10 
     The information processing terminal described in additional aspect 9, the information processing terminal further including a storage device which stores the confidential information to be transmitted to the sensor terminal, in which the control device is configured to erase from the storage device, the confidential information transmitted to the sensor terminal when success of transmission of the confidential information to the sensor terminal has been verified. 
     Though embodiments of the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.