Information processing system, information processing method, and recording medium

Abstract

An information processing system (10) comprises: a first acquisition means (100) that acquires a first feature quantity based on a first echo sound reflected at a first ear of a subject; a second acquisition means (200) that acquires a second feature quantity based on a second echo sound reflected at the second ear of the subject; and a determination means (310) that determines whether or not the subject can be authenticated on the basis of the first feature quantity, the second feature quantity, and the distance between the first acquisition means and the second acquisition means. Such an information processing system makes it possible to perform ear acoustic authentication with high accuracy.

Description

Information processing system, information processing method, and recording medium

[0001] The present disclosure relates to the technical fields of an information processing system, an information processing method, and a recording medium.

[0002] There is known a technology for performing authentication processing of a target (so-called ear acoustic authentication) based on characteristics of the ear canal acquired by utilizing sound reverberation. For example, Patent Literature 1 discloses a technology for performing user authentication based on the authentication result of ear acoustic authentication using earphones and the movement of the user wearing the earphones.

[0003] International Publication No. 2022 / 195792

[0004] An object of the present disclosure is to provide an information processing system, an information processing method, and a recording medium that are capable of performing ear acoustic authentication with high accuracy.

[0005] One aspect of the information processing system disclosed herein includes a first acquisition means for acquiring a first feature based on a first echo that has reverberated in a first ear of a subject, a second acquisition means for acquiring a second feature based on a second echo that has reverberated in a second ear of the subject, and a determination means for determining whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0006] Another aspect of the information processing system of this disclosure includes a first acquisition means that acquires a first echo that has reverberated in a first ear of a subject, a second acquisition means that acquires a second echo that has reverberated in a second ear of the subject, an extraction means that extracts a first feature from the first echo and a second feature from the second echo, and a determination means that determines whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0007] One aspect of the information processing method disclosed herein involves acquiring a first feature based on a first echo that has reverberated in a first ear of a subject using a first acquisition means, acquiring a second feature based on a second echo that has reverberated in a second ear of the subject using a second acquisition means, and determining whether the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0008] One aspect of the recording medium of this disclosure has recorded thereon a computer program for executing an information processing method, which acquires, by a first acquisition means, a first feature based on a first echo that has reverberated in a first ear of a subject, acquires, by a second acquisition means, a second feature based on a second echo that has reverberated in a second ear of the subject, and determines whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0009] 1. A block diagram showing the hardware configuration of a first information processing system. 2. A block diagram showing the terminal configuration of the first information processing system. 3. A flowchart showing the flow of authentication operations in the first information processing system. 4. A block diagram showing the terminal configuration of a second information processing system. 5. A flowchart showing the flow of authentication operations in the second information processing system. 6. A conceptual diagram showing a method for measuring the propagation time of sound in a third information processing system. 7. A flowchart showing the flow of distance calculation operations in the third information processing system. 8. A conceptual diagram showing a method for measuring the propagation time of sound in a fourth information processing system. 9. A flowchart showing the flow of distance calculation operations in the fourth information processing system. 10. A block diagram showing the configurations of a first terminal and a second terminal in a fifth information processing system. 11. A flowchart showing the flow of distance calculation operations in the fifth information processing system. 12. A block diagram showing the configurations of a first terminal and a second terminal in a sixth information processing system. 13. A flowchart showing the flow of distance calculation operations in the sixth information processing system. 14. A block diagram showing the terminal configuration of a seventh information processing system. 15. A flowchart showing the flow of authentication operations in the seventh information processing system.

[0010] Hereinafter, embodiments of an information processing system, an information processing method, and a recording medium will be described with reference to the drawings.

[0011] First Embodiment A first information processing system will be described with reference to FIGS. 1 to 3. FIG.

[0012] (Hardware Configuration) First, the hardware configuration of the first information processing system will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the hardware configuration of the first information processing system.

[0013] 1, a first information processing system 10 includes a processor 11, a RAM (Random Access Memory) 12, a ROM (Read Only Memory) 13, and a storage device 14. The information processing system 10 may further include an input device 15 and an output device 16. The processor 11, RAM 12, ROM 13, storage device 14, input device 15, and output device 16 are connected to each other via a data bus 17. The data bus 17 may be an interface other than a data bus (for example, a LAN, a USB, etc.).

[0014] The processor 11 loads a computer program. For example, the processor 11 is configured to load a computer program stored in at least one of the RAM 12, the ROM 13, and the storage device 14. Alternatively, the processor 11 may load a computer program stored in a computer-readable storage medium using a storage medium reading device (not shown). The processor 11 may acquire (i.e., load) the computer program from a device (not shown) located outside the information processing system 10 via a network interface. The processor 11 controls the RAM 12, the storage device 14, the input device 15, and the output device 16 by executing the loaded computer program. In particular, in this embodiment, when the processor 11 executes the loaded computer program, functional blocks for executing processing related to ear acoustic authentication are realized within the processor 11. In other words, the processor 11 may function as a controller that executes each control in the information processing system 10.

[0015] The processor 11 may be configured as, for example, a central processing unit (CPU), a graphics processing unit (GPU), a field-programmable gate array (FPGA), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or a quantum processor. The processor 11 may be configured as one of these, or may be configured to use multiple processors in parallel.

[0016] The RAM 12 temporarily stores computer programs executed by the processor 11. The RAM 12 temporarily stores data that the processor 11 temporarily uses while it is executing the computer programs. The RAM 12 may be, for example, a dynamic random access memory (D-RAM) or a static random access memory (SRAM). Alternatively, other types of volatile memory may be used instead of the RAM 12.

[0017] The ROM 13 stores computer programs executed by the processor 11. The ROM 13 may also store fixed data. The ROM 13 may be, for example, a programmable read-only memory (PROM) or an erasable read-only memory (EPROM). Alternatively, other types of non-volatile memory may be used instead of the ROM 13.

[0018] The storage device 14 stores data that is to be saved long-term by the information processing system 10. The storage device 14 may operate as a temporary storage device for the processor 11. The storage device may store computer programs executed by the processor 11. The storage device 14 may include, for example, at least one of a hard disk device, a magneto-optical disk device, an SSD (Solid State Drive), and a disk array device.

[0019] The input device 15 is a device that receives input instructions from a user of the information processing system 10. The input device 15 may include, for example, at least one of a keyboard, a mouse, and a touch panel. The input device 15 may be configured as part of a smartphone, a tablet terminal, an earphone-type terminal, a watch-type terminal, a glasses-type or goggle-type HMD (Head Mounted Display) terminal, or the like. The input device 15 may be, for example, a device that includes a microphone and is capable of voice input.

[0020] The output device 16 is a device that outputs information related to the information processing system 10 to the outside. For example, the output device 16 may be a display device (e.g., a display) that can display information related to the information processing system 10. The output device 16 may also be a speaker or the like that can output information related to the information processing system 10 as audio. The output device 16 may be configured as part of a smartphone, a tablet terminal, an earphone-type terminal, a watch-type terminal, a glasses-type or goggle-type HMD terminal, or the like.

[0021] The first information processing system 10 is configured to include a first terminal, a second terminal, and a third terminal, as described below. Each of the components described in Fig. 1 may be configured to be included in at least one of the first terminal, the second terminal, and the third terminal included in the first information processing system 10. Furthermore, some of the components described in Fig. 1 may be configured to be included in an external device (e.g., an external server, a cloud, etc.) different from the first terminal, the second terminal, and the third terminal.

[0022] (Terminal Configuration) Next, the terminal configuration of the first information processing system 10 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the terminal configuration of the first information processing system.

[0023] 2, the first information processing system 10 is configured to include a first terminal 100, a second terminal 200, and a third terminal 300. The first terminal 100, the second terminal 200, and the third terminal 300 are connected, for example, by wireless communication, and are configured to be able to send and receive information to and from each other. The first terminal 100 and the second terminal 200 may also be configured to be able to send and receive information to and from each other via wireless communication or the like.

[0024] The first terminal 100 and the second terminal 200 are each configured as an earphone-type hearable terminal. The first terminal 100 and the second terminal 200 are configured as terminals corresponding to different ears. For example, the first terminal 100 may be configured as an earphone-type terminal for the right ear, and the second terminal 200 may be configured as an earphone-type terminal for the left ear.

[0025] The first terminal 100 includes a first feature acquisition unit 110 as a processing block for realizing its function. The first feature acquisition unit 110 is configured to acquire a first feature based on a first echo sound echoed inside the first ear of the subject. The first feature acquisition unit 110 controls the first terminal 100, for example, attached to the first ear of the subject, to acquire an echo sound signal including characteristics of the first ear of the subject (specifically, characteristics of the shape of the inside of the ear). More specifically, the first feature acquisition unit 110 controls the first terminal 100 to emit sound waves into the first ear of the subject, and acquires an echo sound signal based on the echo sound of the emitted sound waves. The first feature acquisition unit 110 then extracts a first feature from the acquired echo sound signal. On the other hand, the second terminal 200 includes a second feature acquisition unit 210 as a processing block for realizing its function. The second feature amount acquiring unit 210 is configured to be able to acquire a second feature amount based on a second reverberation sound that has reverberated inside the second ear of the subject, by performing the same operation as the above-described first feature amount acquiring unit 110. The first feature amount and the second feature amount are parameters that indicate characteristics of the shapes inside the first and second ears (i.e., the right and left ears) of the subject, and are used for ear acoustic authentication in the determining unit 310, which will be described later.

[0026] The third terminal 300 is configured as, for example, a mobile terminal such as a smartphone, a tablet terminal, a watch-type terminal, or a glasses-type or goggle-type HMD terminal, or as a terminal such as a personal computer or a server. The third terminal 300 includes a determination unit 310 as a processing block for realizing its functions. The determination unit 310 is configured to be capable of receiving a first feature from a first feature acquisition unit 110 in the first terminal 100. The determination unit 310 is also configured to be capable of receiving a second feature from a second feature acquisition unit 210 in the second terminal 200. The determination unit 310 is further configured to be capable of acquiring an inter-terminal distance, which is the distance between the first terminal 100 and the second terminal 200. The inter-terminal distance may be a value calculated by, for example, a device external to the system. Alternatively, the inter-terminal distance may be a value calculated by any of the first terminal 100, the second terminal 200, and the third terminal. The configuration for calculating the inter-terminal distance will be described in detail in another embodiment described later.

[0027] The determination unit 310 is configured to determine whether or not a target can be authenticated based on the first feature received from the first feature acquisition unit 110, the second feature received from the second feature acquisition unit 210, and the inter-terminal distance (i.e., the distance between the first terminal 100 and the second terminal 200). Specifically, the determination unit 310 determines whether or not the first feature and the second feature match the features of a pre-registered user. For example, the determination unit 310 determines whether or not the degree of match between the first feature and the second feature and the features of the registered user exceeds a predetermined determination threshold. The determination unit 310 also determines whether or not the inter-terminal distance is normal. For example, the determination unit 310 determines whether or not the inter-terminal distance falls within a predetermined range. The predetermined range here is a threshold for determining whether the first terminal 100 and the second terminal 200 are worn on the target's right and left ears, respectively, and is set, for example, according to the average distance between a human's right and left ears.

[0028] The determination unit 310 may determine whether the target can be authenticated based on the results of the determination using the first feature amount and the second feature amount described above and the results of the determination using the inter-terminal distance. For example, the determination unit 310 may determine that the target is a registered user if the degree of match between the first feature amount and the second feature amount and the feature amount of the registered user exceeds a predetermined determination threshold and the inter-terminal distance is within a predetermined range. On the other hand, the determination unit 310 may determine that the target is not a registered user if the degree of match between the first feature amount and the second feature amount and the feature amount of the registered user exceeds the predetermined determination threshold but the inter-terminal distance is not within the predetermined range. Furthermore, the determination unit 310 may determine that the target is not a registered user if the degree of match between the first feature amount and the second feature amount and the feature amount of the registered user does not exceed the predetermined determination threshold even if the inter-terminal distance is within the predetermined range.

[0029] The determination unit 310 may have a function of outputting a determination result regarding whether or not the target can be authenticated. For example, the determination unit 310 may be configured to display the determination result on a display or output the determination result as audio through a speaker. Furthermore, the determination unit 310 may permit a predetermined operation on the third terminal 300 when it determines that the target is a registered user. The predetermined operation may include all operations executable on the third terminal 300, or may be a portion of the operations executable on the third terminal 300. For example, if the third terminal 300 is configured as a smartphone, the third terminal 300 may be configured to unlock the lock screen of the smartphone on the condition that it is determined that the target is a registered user. Alternatively, the third terminal 300 may be configured to allow the use of a specific app on the smartphone on the condition that it is determined that the target is a registered user.

[0030] The function of the above-described determination unit 310 may be provided in either the first terminal 100 or the second terminal 200. That is, the determination unit 310 may be provided in the first terminal 100 or the second terminal 200. In this case, the first information processing device 10 may be configured without including the third terminal 300.

[0031] (Authentication Operation) Next, the flow of the authentication operation (i.e., the operation of acquiring the first feature amount, the second feature amount, and the inter-terminal distance and determining whether or not to authenticate the target) in the first information processing system 10 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the flow of the authentication operation in the first information processing system.

[0032] 3 , when the authentication operation by the first information processing system 10 is initiated, the first feature acquisition unit 110 in the first terminal 100 acquires a first feature based on a first echo sound reflected in the first ear of the target (step S101). The second feature acquisition unit 210 in the second terminal 200 acquires a second feature based on a second echo sound reflected in the second ear of the target (step S102). Note that the processes in steps S101 and S102 may be executed one after the other, or may be executed simultaneously in parallel. Each of the first feature and the second feature is output to the determination unit 310 in the third terminal 300.

[0033] Next, the determination unit 310 acquires the inter-terminal distance, which is the distance between the first terminal 100 and the second terminal 200 (step S103). The determination unit 310 then determines whether the inter-terminal distance is within a predetermined range (step S104). If the inter-terminal distance is not within the predetermined range (step S104: NO), the determination unit 310 determines that the target is not a registered user (step S107). If the inter-terminal distance is not within the predetermined range, it can be determined that the target is not wearing the first terminal 100 and the second terminal 200 on their right and left ears, respectively (for example, they may be attempting fraud, such as impersonation). Therefore, the determination unit 310 may determine that the target is not a registered user if the inter-terminal distance is not within the predetermined range.

[0034] If the inter-terminal distance is within a predetermined range (step S104: NO), the determination unit 310 determines whether the first feature amount and the second feature amount match the feature amount of a pre-registered registered user (step S105). If the first feature amount and the second feature amount match the feature amount of a registered user (step S105: YES), the determination unit 310 determines that the target is a registered user (step S106). On the other hand, if the first feature amount and the second feature amount do not match the feature amount of a registered user (step S105: NO), the determination unit 310 determines that the target is not a registered user (step S107).

[0035] (Technical Effects) Next, technical effects obtained by the first information processing system 10 will be described.

[0036] As described with reference to FIGS. 1 to 3 , the first information processing system 10 determines whether a target can be authenticated based on the first feature acquired by the first terminal 100, the second feature acquired by the second terminal 200, and the distance between the first terminal 100 and the second terminal 200. This allows ear acoustic authentication to be performed with high accuracy. For example, authentication using only the first feature and the second feature cannot prevent impersonation by a third party who has fraudulently obtained the first feature and the second feature. However, the first information processing system also uses the inter-terminal distance between the first terminal 100 and the second terminal 200 for authentication, thereby effectively preventing fraud in authentication. For example, if the first terminal 100 and the second terminal 200 are not worn on the right and left ears, the inter-terminal distance will be an abnormal value. In such a case, fraud is suspected and authentication of the target can be prevented from succeeding.

[0037] Second Embodiment A second information processing system 10 will be described with reference to Figures 4 and 5. The second information processing system 10 differs only in part of its configuration and operation from the first information processing system 10 described above, and other parts may be similar to the first information processing system 10. Therefore, the following will describe in detail the parts that differ from the first embodiment, and will omit a description of other overlapping parts as appropriate.

[0038] (Terminal Configuration) First, the terminal configuration of the second information processing system 10 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the terminal configuration of the second information processing system. Note that in Fig. 4, the same elements as those shown in Fig. 2 are denoted by the same reference numerals.

[0039] 4, the second information processing system 10 is configured to include a first terminal 100, a second terminal 200, and a third terminal 300. The third terminal 300 in the second information processing system 10 includes, as processing blocks for realizing its functions, a determination unit 310 and an inter-terminal distance calculation unit 320. That is, the third terminal 300 in the second information processing system 10 further includes the inter-terminal distance calculation unit 320 in addition to the configuration described in the first embodiment (see FIG. 2).

[0040] Terminal-to-terminal distance calculation unit 320 is configured to be able to calculate the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200. There are no particular limitations on the method used by terminal-to-terminal distance calculation unit 320 to calculate the terminal-to-terminal distance. Specific examples of methods for calculating the terminal-to-terminal distance will be described in detail in other embodiments described later.

[0041] The function of inter-terminal distance calculation unit 320 may be provided in either first terminal 100 or second terminal 200. That is, inter-terminal distance calculation unit 320 may be provided in first terminal 100 or second terminal 200. In this case, second information processing device 10 may be configured without including third terminal 300.

[0042] (Authentication Operation) Next, the flow of authentication operation in the second information processing system 10 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the flow of authentication operation in the second information processing system. Note that in Fig. 5, the same processes as those shown in Fig. 3 are denoted by the same reference numerals.

[0043] 5 , when the authentication operation by the second information processing system 10 is started, the first feature acquisition unit 110 in the first terminal 100 acquires a first feature based on a first echo sound reflected in the first ear of the target (step S101). The second feature acquisition unit 210 in the second terminal 200 acquires a second feature based on a second echo sound reflected in the second ear of the target (step S102). The first feature and the second feature are each output to the determination unit 310 in the third terminal 300.

[0044] Next, terminal-to-terminal distance calculation unit 320 calculates the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200 (step S201). The terminal-to-terminal distance calculated by terminal-to-terminal distance calculation unit 320 is output to determination unit 310 in third terminal 300.

[0045] Next, the determination unit 310 determines whether the inter-terminal distance is within a predetermined range (step S104). If the inter-terminal distance is not within the predetermined range (step S104: NO), the determination unit 310 determines that the target is not a registered user (step S107).

[0046] If the inter-terminal distance is within a predetermined range (step S104: NO), the determination unit 310 determines whether the first feature amount and the second feature amount match the feature amount of a pre-registered registered user (step S105). If the first feature amount and the second feature amount match the feature amount of a registered user (step S105: YES), the determination unit 310 determines that the target is a registered user (step S106). On the other hand, if the first feature amount and the second feature amount do not match the feature amount of a registered user (step S105: NO), the determination unit 310 determines that the target is not a registered user (step S107).

[0047] (Technical Effects) Next, technical effects obtained by the second information processing system 10 will be described.

[0048] 4 and 5, in the second information processing system 10, the inter-terminal distance is calculated by the inter-terminal distance calculation unit 320. In this way, it is possible to more appropriately execute authentication processing using the inter-terminal distance.

[0049] <Third Embodiment> A third information processing system 10 will be described with reference to Figures 6 and 7. The third information processing system 10 differs only in part of the configuration and operation from the second information processing system 10 described above, and other parts may be similar to the second information processing system 10. Therefore, the following will describe in detail the parts that differ from the embodiments already described, and will omit explanations of other overlapping parts as appropriate.

[0050] (Terminal Configuration) First, the terminal configuration of the third information processing system 10 will be described with reference to Fig. 6. Fig. 6 is a conceptual diagram showing a method for measuring the sound propagation time in the third information processing system.

[0051] As shown in FIG. 6 , the third information processing system 10 measures the sound transmission time between the first terminal 100 and the second terminal 200. For example, a speaker provided in the first terminal 100 transmits sound. Then, a microphone provided in the second terminal 200 receives the sound transmitted from the first terminal 100. By performing this operation, the time from when the first terminal 100 transmits sound to when the second terminal 200 receives the sound can be calculated as the sound transmission time between the first terminal 100 and the second terminal 200. Note that the above-described operation may be repeatedly performed to calculate the sound transmission time more accurately. In this case, the average value of the measured times may be treated as the sound transmission time.

[0052] Sound emitted from the first terminal 100 may be transmitted to the second terminal 200 by bone conduction. For example, sound emitted from the first terminal 100 worn on the right ear of a subject may be transmitted through the ears and facial bones of the subject and received by the second terminal 200 worn on the left ear of the subject. By using bone conduction, it is possible to accurately measure the transmission time of sound even when the environmental sound is relatively loud.

[0053] In the above example, a configuration has been given in which sound is transmitted from the first terminal 100 to the second terminal 200, but a configuration in which sound is transmitted from the second terminal 200 to the first terminal 100 may also be used. That is, there are no particular limitations on which terminal transmits the sound and which terminal receives the sound. Furthermore, a configuration may be used in which sound can be transmitted from both the first terminal 100 and the second terminal 200, and the operation of transmitting sound from the first terminal 100 to the second terminal 200 and the operation of transmitting sound from the second terminal 200 to the first terminal 100 may be repeated to measure the sound transmission time.

[0054] Terminal-to-terminal distance calculation unit 320 in third information processing system 10 is configured to be able to calculate the distance between first terminal 100 and second terminal 200 based on the sound transmission time between first terminal 100 and second terminal 200 described above. The sound transmission time between first terminal 100 and second terminal 200 becomes longer as the distance between first terminal 100 and second terminal 200 increases. Therefore, if the relationship between the sound transmission time and the terminal-to-terminal distance is known in advance, it is possible to calculate the terminal-to-terminal distance from the measured sound transmission time.

[0055] (Distance Calculation Operation) Next, the flow of the distance calculation operation in the third information processing system 10 (i.e., the operation when calculating the distance between terminals corresponding to step S201 in Fig. 5) will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the flow of the distance calculation operation in the third information processing system.

[0056] 7, when the distance calculation operation is started in the third information processing system 10, the first terminal 100 first emits a sound (step S301), and the second terminal 200 then receives the sound emitted from the first terminal 100 (step S302).

[0057] Next, terminal-to-terminal distance calculation unit 320 calculates the transmission time of sound between first terminal 100 and second terminal 200 (step S303). Specifically, terminal-to-terminal distance calculation unit 320 may calculate the time required from when first terminal 100 transmits a sound until second terminal 200 receives the sound.

[0058] Next, terminal-to-terminal distance calculation unit 320 calculates the distance between first terminal 100 and second terminal 200 based on the sound transmission time between first terminal 100 and second terminal 200 (step S304). The terminal-to-terminal distance calculated by terminal-to-terminal distance calculation unit 320 is output to determination unit 310.

[0059] (Technical Effects) Next, technical effects obtained by the third information processing system 10 will be described.

[0060] 6 and 7 , in the third information processing system 10, the inter-terminal distance is calculated based on the propagation time of sound between the first terminal 100 and the second terminal 200. In this way, it is possible to accurately calculate the inter-terminal distance with a simple configuration.

[0061] <Fourth Embodiment> A fourth information processing system 10 will be described with reference to Figures 8 and 9. Note that the fourth information processing system 10 differs only in part of the configuration and operation from the second information processing system 10 described above, and other parts may be similar to the second information processing system 10. Therefore, hereinafter, only the parts that differ from the embodiments already described will be described in detail, and explanations of other overlapping parts will be omitted as appropriate.

[0062] (Terminal Configuration) First, the terminal configuration of the fourth information processing system 10 will be described with reference to Fig. 8. Fig. 8 is a conceptual diagram showing a method for measuring the propagation time of sound in the fourth information processing system.

[0063] 8, the fourth information processing system 10 measures the transmission time of sound between the first terminal 100, the second terminal 200, and a reference terminal. The reference terminal may be a terminal different from the first terminal 100 and the second terminal 200. Therefore, if the fourth information processing system 10 includes a third terminal 300, the third terminal 300 may be treated as the reference terminal. In the following description, the third terminal 300 is assumed to be the reference terminal.

[0064] In the fourth information processing system, the transmission time of sound between the first terminal 100 and the third terminal 300 is measured. For example, a speaker provided in the first terminal 100 emits sound. Then, a microphone provided in the third terminal 300 receives the sound emitted from the first terminal 100. By performing this operation, the time from when the first terminal 100 emits sound to when the third terminal 300 receives the sound can be calculated as the transmission time of sound between the first terminal 100 and the third terminal 300.

[0065] The fourth information processing system further measures the transmission time of sound between second terminal 200 and third terminal 300. For example, a speaker provided in second terminal 200 emits sound. Then, a microphone provided in third terminal 300 receives the sound emitted from second terminal 200. By performing this operation, the time from when second terminal 200 emits sound to when third terminal 300 receives the sound can be calculated as the transmission time of sound between second terminal 100 and third terminal 300.

[0066] In order to calculate the sound transmission time more accurately, the above-described operation of transmitting and receiving sound may be repeatedly performed. In this case, the average value of the measured times may be treated as the sound transmission time. Furthermore, if the third terminal 300 is a terminal that is used by being brought into contact with an object, or if the third terminal 300 can be brought into contact with an object, it is also possible to measure the sound transmission time using bone conduction, as described in the second embodiment.

[0067] In the above example, a configuration has been given in which sound is transmitted from the first terminal 100 and the second terminal 200 toward the third terminal 200, but a configuration in which sound is transmitted from the third terminal 300 toward the first terminal 100 and the second terminal 200 may also be used. Alternatively, a configuration may be used in which sound can be transmitted from both the first terminal 100 and the second terminal 200 side and the third terminal 300 side, and the operation of transmitting sound from the first terminal 100 and the second terminal 200 toward the third terminal 300 and the operation of transmitting sound from the third terminal 300 toward the first terminal 100 and the second terminal 200 may be repeated to measure the sound transmission time.

[0068] The inter-terminal distance calculation unit 320 in the fourth information processing system 10 is configured to be able to calculate the distance between the first terminal 100 and the second terminal 200 based on the sound transmission time between the first terminal 100 and the third terminal 300 and the sound transmission time between the second terminal 200 and the third terminal 300 described above. The sound transmission time between the terminals becomes longer as the distance between the terminals increases. Therefore, the distance between the first terminal 100 and the third terminal 300 can be calculated using the sound transmission time between the first terminal 100 and the third terminal 300. Similarly, the distance between the second terminal 200 and the third terminal 300 can be calculated using the sound transmission time between the second terminal 200 and the third terminal 300. Then, by using the distance between the first terminal 100 and the third terminal 300 and the distance between the second terminal 200 and the third terminal 300, it is possible to calculate the distance between the first terminal 100 and the second terminal 200 (i.e., the distance between the terminals), for example, using triangulation.

[0069] (Distance Calculation Operation) Next, the flow of the distance calculation operation in the fourth information processing system 10 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the flow of the distance calculation operation in the fourth information processing system.

[0070] 9 , when the distance calculation operation in the fourth information processing system 10 starts, first, the first terminal 100 transmits a sound (step S401). Then, the third terminal 300, which is the reference terminal, receives the sound transmitted from the first terminal 100 (step S402). Thereafter, the inter-terminal distance calculation unit 320 calculates the transmission time of the sound between the first terminal 100 and the third terminal 300 (step S403).

[0071] Next, second terminal 200 transmits a sound (step S404). Then, third terminal 300, which is the reference terminal, receives the sound transmitted from second terminal 200 (step S405). Thereafter, inter-terminal distance calculation unit 320 calculates the transmission time of the sound between second terminal 200 and third terminal 300 (step S406).

[0072] Next, terminal-to-terminal distance calculation unit 320 calculates the distance between first terminal 100 and second terminal 200 based on the sound transmission time between first terminal 100 and third terminal 300 and the sound transmission time between second terminal 200 and third terminal 300 (step S407). The terminal-to-terminal distance calculated by terminal-to-terminal distance calculation unit 320 is output to determination unit 310.

[0073] (Technical Effects) Next, technical effects obtained by the fourth information processing system 10 will be described.

[0074] As described with reference to Figures 8 and 9, in the fourth information processing system 10, the inter-terminal distance is calculated based on the sound transmission time between the first terminal 100 and the third terminal 300 and the sound transmission time between the second terminal 200 and the third terminal 300. In this way, it is possible to accurately calculate the inter-terminal distance with a simple configuration. Furthermore, in particular, in the fourth information processing system 10, even if it is not possible to measure the sound transmission time between the first terminal 100 and the second terminal 200 as in the third information processing system (see Figure 6), it is possible to appropriately calculate the inter-terminal distance using the sound transmission time to the third terminal 300, which is the reference terminal.

[0075] Fifth Embodiment A fifth information processing system 10 will be described with reference to Figures 10 and 11. The fifth information processing system 10 differs only in part of the configuration and operation from the second information processing system 10 described above, and other parts may be the same as the second information processing system 10. Therefore, the following will describe in detail the parts that differ from the embodiments already described, and will omit explanations of other overlapping parts as appropriate.

[0076] (Terminal Configuration) First, the terminal configuration of the fifth information processing system 10 will be described with reference to Fig. 10. Fig. 10 is a block diagram showing the configuration of the first terminal and the second terminal in the fifth information processing system.

[0077] 10 , in the fifth information processing system 10, an acceleration sensor 150 is provided in the first terminal 100. The acceleration sensor 150 is configured to be able to detect the acceleration of the first terminal 100. In addition, in the fifth information processing system 10, an acceleration sensor 250 is also provided in the second terminal 200. The acceleration sensor 250 is configured to be able to detect the acceleration of the second terminal 200.

[0078] Terminal-to-terminal distance calculation unit 320 in the fifth information processing system is configured to calculate the distance traveled by first terminal 100 based on acceleration detected by acceleration sensor 150 in first terminal 100. Terminal-to-terminal distance calculation unit 320 is also configured to calculate the distance traveled by second terminal 200 based on acceleration detected by acceleration sensor 250 in second terminal 200. Terminal-to-terminal distance calculation unit 320 is then configured to calculate the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200, based on the distance traveled by first terminal 100 and the distance traveled by second terminal 200. For example, terminal-to-terminal distance calculation unit 320 brings first terminal 100 and second terminal 200 into contact with each other, and sets the positions in this state as initial positions. Terminal-to-terminal distance calculation unit 320 then calculates the terminal-to-terminal distance based on the distance traveled by first terminal 100 from the initial position and the distance traveled by second terminal 200 from the initial position.

[0079] In the example described above, a configuration has been given in which acceleration sensors 150 and 160 are provided in both first terminal 100 and second terminal 200, but an acceleration sensor may be provided in only one of first terminal 100 and second terminal 200. In this case, it is possible to measure the movement distance of only one of first terminal 100 and second terminal 200, but it is possible to calculate the distance between the terminals by preventing the other terminal from moving.

[0080] (Distance Calculation Operation) Next, the flow of the distance calculation operation in the fifth information processing system 10 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing the flow of the distance calculation operation in the fifth information processing system.

[0081] 11 , when the distance calculation operation in the fifth information processing system 10 is started, first, the inter-terminal distance calculation unit 320 acquires the acceleration detected by the acceleration sensor 150 in the first terminal 100 (step S501). Then, the inter-terminal distance calculation unit 320 calculates the travel distance of the first terminal 100 based on the acquired acceleration of the first terminal 100 (step S502).

[0082] Similarly, terminal-to-terminal distance calculation unit 320 acquires the acceleration detected by acceleration sensor 250 in second terminal 200 (step S503). Then, terminal-to-terminal distance calculation unit 320 calculates the travel distance of second terminal 200 based on the acquired acceleration of second terminal 200 (step S504).

[0083] Next, terminal-to-terminal distance calculation unit 320 calculates the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200, based on the movement distance of first terminal 100 and the movement distance of second terminal 200 (step S505). Note that the terminal-to-terminal distance calculated by terminal-to-terminal distance calculation unit 320 is output to determination unit 310.

[0084] (Technical Effects) Next, technical effects obtained by the fifth information processing system 10 will be described.

[0085] 10 and 11 , in the fifth information processing system 10, the movement distances of the first terminal 100 and the second terminal 200 are measured using the acceleration sensors 150 and 250, and the distance between the terminals is calculated based on the measured movement distances of each terminal. In this way, it is possible to accurately calculate the distance between the terminals with a simple configuration.

[0086] Sixth Embodiment A sixth information processing system 10 will be described with reference to Figures 12 and 13. The sixth information processing system 10 differs only in part of its configuration and operation from the second information processing system 10 described above, and other parts may be the same as the second information processing system 10. Therefore, the following will describe in detail the parts that differ from the embodiments already described, and will omit explanations of other overlapping parts as appropriate.

[0087] (Terminal Configuration) First, the terminal configuration of the sixth information processing system 10 will be described with reference to Fig. 12. Fig. 12 is a block diagram showing the configuration of the first terminal and the second terminal in the sixth information processing system.

[0088] 12 , in the sixth information processing system 10, a GPS receiver 160 is provided in the first terminal 100. The GPS receiver 160 is configured to receive signals from GPS satellites and detect the position of the first terminal 100. In the fifth information processing system 10, a GPS receiver 260 is also provided in the second terminal 200. The GPS receiver 260 is configured to receive signals from GPS satellites and detect the position of the second terminal 200.

[0089] Terminal-to-terminal distance calculation unit 320 in the fifth information processing system is configured to be able to calculate the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200, based on the position of first terminal 100 detected by GPS receiver 160 and the position of second terminal 200 detected by GPS receiver 260. For example, terminal-to-terminal distance calculation unit 320 calculates the difference between the position of first terminal 100 and the position of second terminal 200, and sets this as the terminal-to-terminal distance.

[0090] (Distance Calculation Operation) Next, the flow of the distance calculation operation in the sixth information processing system 10 will be described with reference to Fig. 13. Fig. 13 is a flowchart showing the flow of the distance calculation operation in the sixth information processing system.

[0091] 13 , when the distance calculation operation in the sixth information processing system 10 is started, first, the inter-terminal distance calculation unit 320 acquires the position of the first terminal 100 detected by the GPS receiver 160 in the first terminal 100 (step S601). The inter-terminal distance calculation unit 320 also acquires the position of the second terminal 200 detected by the GPS receiver 260 in the second terminal 200 (step S602).

[0092] Next, terminal-to-terminal distance calculation unit 320 calculates the terminal-to-terminal distance, which is the distance between first terminal 100 and second terminal 200, based on the positions of first terminal 100 and second terminal 200 (step S603). Note that the terminal-to-terminal distance calculated by terminal-to-terminal distance calculation unit 320 is output to determination unit 310.

[0093] (Technical Effects) Next, technical effects obtained by the sixth information processing system 10 will be described.

[0094] 12 and 13 , in the sixth information processing system 10, the positions of the first terminal 100 and the second terminal 200 are measured using GPS, and the distance between the terminals is calculated based on the measured positions of each terminal. In this way, it is possible to accurately calculate the distance between the terminals with a simple configuration.

[0095] Seventh Embodiment A seventh information processing system 10 will be described with reference to Figures 14 and 15. The seventh information processing system 10 differs only in part of the configuration and operation from the first to sixth information processing systems 10 described above, and other parts may be similar to the first to seventh information processing systems 10. Therefore, the following will describe in detail the parts that differ from the embodiments already described, and will omit explanations of other overlapping parts as appropriate.

[0096] (Terminal Configuration) First, the terminal configuration of the seventh information processing system 10 will be described with reference to Fig. 14. Fig. 14 is a block diagram showing the terminal configuration of the seventh information processing system. Note that in Fig. 14, the same elements as those shown in Fig. 2 are denoted by the same reference numerals.

[0097] 14 , the seventh information processing system 10 includes a first terminal 100, a second terminal 200, and a third terminal 300. The first terminal 100 includes a first echo acquisition unit 120 as a processing block for realizing its functions. The first echo acquisition unit 120 is configured to acquire a first echo that has echoed inside the target's first ear. The first echo acquisition unit 110 controls the first terminal 100 to transmit sound waves into the target's first ear and acquires an echo signal based on the echo of the transmitted sound waves. On the other hand, the second terminal 200 includes a second echo acquisition unit 220 as a processing block for realizing its functions. The second echo acquisition unit 220 is configured to acquire a second echo that has echoed inside the target's second ear by performing the same operation as the first echo acquisition unit 120 described above. The first echo acquired by the first echo acquisition unit 120 and the second echo acquired by the second echo acquisition unit 220 are configured to be output to the third terminal.

[0098] The third terminal 300 includes a determination unit 310 and a feature extraction unit 330 as processing blocks for realizing its functions. That is, the third terminal 300 in the seventh information processing system further includes the feature extraction unit 330 in addition to the configuration described in the first embodiment (see FIG. 2 ). The feature extraction unit 330 is configured to be able to extract a first feature from the first echo acquired by the first echo acquisition unit 120. Furthermore, the feature extraction unit 330 is configured to be able to extract a second feature from the second echo acquired by the second echo acquisition unit 220. The first feature and second feature extracted by the feature extraction unit 330 are configured to be output to the determination unit 310.

[0099] (Authentication Operation) Next, the flow of authentication operation in the seventh information processing system 10 will be described with reference to Fig. 15. Fig. 15 is a flowchart showing the flow of authentication operation in the seventh information processing system. Note that in Fig. 15, the same processes as those shown in Fig. 3 are denoted by the same reference numerals.

[0100] 5 , when the authentication operation by the seventh information processing system 10 is initiated, the first echo acquisition unit 120 in the first terminal 100 acquires the first echo that has reverberated in the first ear of the target (step S701). The second echo acquisition unit 220 in the second terminal 200 acquires the second echo that has reverberated in the second ear of the target (step S702). Note that the processes of steps S701 and S702 described above may be executed one after the other, or may be executed simultaneously in parallel. The first echo and the second echo are each output to the third terminal 300.

[0101] Next, the feature extracting unit 330 in the third terminal extracts a first feature from the first echo acquired by the first echo acquiring unit 120. The feature extracting unit 330 also extracts a second feature from the second echo acquired by the second echo acquiring unit 220 (step S703). Each of the first feature and the second feature is output to the determining unit 310.

[0102] Next, determination unit 310 of the third terminal acquires the inter-terminal distance, which is the distance between first terminal 100 and second terminal 200 (step S704). Then, determination unit 310 determines whether the inter-terminal distance is within a predetermined range (step S705). Note that if the inter-terminal distance is not within the predetermined range (step S705: NO), determination unit 310 determines that the target is not a registered user (step S708).

[0103] If the inter-terminal distance is within a predetermined range (step S705: NO), the determination unit 310 determines whether the first feature amount and the second feature amount extracted by the feature amount extraction unit 330 match the feature amount of a pre-registered user (step S706). If the first feature amount and the second feature amount match the feature amount of a registered user (step S706: YES), the determination unit 310 determines that the target is a registered user (step S707). On the other hand, if the first feature amount and the second feature amount do not match the feature amount of a registered user (step S706: NO), the determination unit 310 determines that the target is not a registered user (step S708).

[0104] (Technical Effects) Next, technical effects obtained by the seventh information processing system 10 will be described.

[0105] 14 and 15 , in the seventh information processing system 10, the first terminal 100 and the second terminal 200 acquire the first reverberation sound and the second reverberation sound, and the third terminal 300 extracts the first feature amount and the second feature amount based on the first reverberation sound and the second reverberation sound. In this way, it is possible to simplify the configuration of the first terminal 100 and the second terminal 200. Specifically, since the first terminal 100 and the second terminal 200 do not need to have a configuration for extracting feature amounts from the reverberation sound, it is possible to simplify the configuration of the first terminal 100 and the second terminal 200 compared to the configuration described in the first embodiment (see FIG. 2 ).

[0106] The scope of each embodiment also includes a processing method in which a program that operates the configuration of each embodiment to realize the functions of the above-described embodiments is recorded on a recording medium, the program recorded on the recording medium is read as code, and the program is executed on a computer. In other words, a computer-readable recording medium is also included in the scope of each embodiment. Furthermore, each embodiment includes not only a recording medium on which the above-described program is recorded, but also the program itself.

[0107] Examples of recording media that can be used include floppy disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, magnetic tapes, non-volatile memory cards, and ROMs. Furthermore, the scope of each embodiment is not limited to programs that execute processes by themselves, but also includes programs that execute processes by operating on an OS in conjunction with other software or expansion board functions. Furthermore, the program itself may be stored on a server, and part or all of the program may be downloadable from the server to a user terminal. The program may be provided to the user in, for example, a SaaS (Software as a Service) format.

[0108] <Supplementary Notes> The above-described embodiment may be further described as in the following supplementary notes, but is not limited to the following.

[0109] (Supplementary Note 1) The information processing system described in Supplementary Note 1 is an information processing system including a first acquisition means that acquires a first feature based on a first echo that has reverberated in a first ear of a target, a second acquisition means that acquires a second feature based on a second echo that has reverberated in a second ear of the target, and a determination means that determines whether or not the target can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0110] (Supplementary Note 2) The information processing system according to Supplementary Note 2 is the information processing system according to Supplementary Note 1, further comprising a distance calculation means for calculating a distance between the first acquisition means and the second acquisition means.

[0111] (Supplementary Note 3) The information processing system described in Supplementary Note 3 is the information processing system described in Supplementary Note 2, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a transmission time of sound between the first acquisition means and the second acquisition means.

[0112] (Supplementary Note 4) The information processing system described in Supplementary Note 4 is the information processing system described in Supplementary Note 3, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a transmission time of sound by bone conduction between the first acquisition means and the second acquisition means.

[0113] (Appendix 5) The information processing system described in Appendix 5 is the information processing system described in Appendix 2, further comprising a reference terminal different from the first acquisition means and the second acquisition means, and the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on the transmission time of sound between the first acquisition means and the reference terminal and the transmission time of sound between the second acquisition means and the reference terminal.

[0114] (Appendix 6) The information processing system described in Appendix 6 is the information processing system described in Appendix 2, wherein the distance calculation means uses an acceleration sensor provided in at least one of the first acquisition means and the second acquisition means to calculate a distance traveled by at least one of the first acquisition means and the second acquisition means, and calculates the distance between the first acquisition means and the second acquisition means based on the distance traveled.

[0115] (Supplementary Note 7) The information processing system described in Supplementary Note 7 is the information processing system described in Supplementary Note 2, wherein the distance calculation means detects the positions of the first acquisition means and the second acquisition means using a GPS (Global Positioning System), and calculates the distance between the first acquisition means and the second acquisition means based on the positions of the first acquisition means and the second acquisition means.

[0116] (Appendix 8) The information processing system described in Appendix 8 is an information processing system including a first acquisition means that acquires a first echo that has reverberated in a first ear of a subject, a second acquisition means that acquires a second echo that has reverberated in a second ear of the subject, an extraction means that extracts a first feature from the first echo and a second feature from the second echo, and a determination means that determines whether the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0117] (Supplementary Note 9) The information processing method described in Supplementary Note 9 is an information processing method that acquires, by a first acquisition means, a first feature based on a first echo that has reverberated in a first ear of a target, acquires, by a second acquisition means, a second feature based on a second echo that has reverberated in a second ear of the target, and determines whether the target can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0118] (Supplementary Note 10) The recording medium described in Supplementary Note 10 is a recording medium having recorded thereon a computer program for executing an information processing method, which acquires, by a first acquisition means, a first feature amount based on a first echo that has reverberated in a first ear of a subject, acquires, by a second acquisition means, a second feature amount based on a second echo that has reverberated in a second ear of the subject, and determines whether the subject can be authenticated based on the first feature amount, the second feature amount, and the distance between the first acquisition means and the second acquisition means.

[0119] (Supplementary Note 11) The computer program described in Supplementary Note 11 is a computer program for executing an information processing method, which acquires, by a first acquisition means, a first feature based on a first echo that has reverberated in a first ear of a target, acquires, by a second acquisition means, a second feature based on a second echo that has reverberated in a second ear of the target, and determines whether the target can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0120] (Supplementary Note 12) The information processing system according to Supplementary Note 12 is the information processing system according to Supplementary Note 8, further comprising a distance calculation means for calculating a distance between the first acquisition means and the second acquisition means.

[0121] (Appendix 13) The information processing system described in Appendix 13 is the information processing system described in Appendix 12, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a transmission time of sound between the first acquisition means and the second acquisition means.

[0122] (Appendix 14) The information processing system described in Appendix 14 is the information processing system described in Appendix 12, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a transmission time of sound by bone conduction between the first acquisition means and the second acquisition means.

[0123] (Appendix 15) The information processing system described in Appendix 15 is the information processing system described in Appendix 12, further comprising a reference terminal different from the first acquisition means and the second acquisition means, and the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on the transmission time of sound between the first acquisition means and the reference terminal and the transmission time of sound between the second acquisition means and the reference terminal.

[0124] (Appendix 16) The information processing system described in Appendix 16 is the information processing system described in Appendix 12, wherein the distance calculation means uses an acceleration sensor provided in at least one of the first acquisition means and the second acquisition means to calculate a movement distance of at least one of the first acquisition means and the second acquisition means, and calculates the distance between the first acquisition means and the second acquisition means based on the movement distance.

[0125] (Supplementary Note 17) The information processing system described in Supplementary Note 17 is the information processing system described in Supplementary Note 12, wherein the distance calculation means detects the positions of the first acquisition means and the second acquisition means using a GPS (Global Positioning System), and calculates the distance between the first acquisition means and the second acquisition means based on the positions of the first acquisition means and the second acquisition means.

[0126] (Appendix 18) The information processing method described in Appendix 18 is an information processing method that acquires a first echo that has reverberated in a first ear of a subject using a first acquisition means, acquires a second echo that has reverberated in a second ear of the subject using a second acquisition means, extracts a first feature from the first echo, extracts the second feature from the second echo, and determines whether the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0127] (Supplementary Note 19) The recording medium described in Supplementary Note 19 is a recording medium having recorded thereon a computer program for executing an information processing method, which includes acquiring a first echo that has reverberated in a first ear of a subject with a first acquisition means, acquiring a second echo that has reverberated in a second ear of the subject with a second acquisition means, extracting a first feature from the first echo, extracting a second feature from the second echo, and determining whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0128] (Supplementary Note 20) The computer program described in Supplementary Note 20 is a computer program for executing an information processing method that acquires, with a first acquisition means, a first echo that has reverberated in a first ear of a subject, acquires, with a second acquisition means, a second echo that has reverberated in a second ear of the subject, extracts a first feature from the first echo, extracts the second feature from the second echo, and determines whether the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

[0129] This disclosure may be modified as appropriate within the scope that does not contradict the gist or idea of ​​the invention that can be read from the claims and the entire specification, and information processing systems, information processing methods, and recording media that involve such modifications are also included in the technical idea of ​​this disclosure.

[0130] REFERENCE SIGNS LIST 10 Information processing system 11 Processor 100 First terminal 110 First feature acquisition unit 120 First echo acquisition unit 150 Acceleration sensor 160 GPS receiver 200 Second terminal 210 Second feature acquisition unit 220 Second echo acquisition unit 250 Acceleration sensor 260 GPS receiver 300 Third terminal 310 Determination unit 320 Terminal-to-terminal distance calculation unit 330 Feature extraction unit

Claims

1. An information processing system comprising: a first acquisition means for acquiring a first feature based on a first echo sound reflected at a first ear of a subject; a second acquisition means for acquiring a second feature based on a second echo sound reflected at a second ear of the subject; and a determination means for determining whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

2. The information processing system according to claim 1, further comprising a distance calculation means for calculating a distance between said first acquisition means and said second acquisition means.

3. The information processing system according to claim 2, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a transmission time of sound between the first acquisition means and the second acquisition means.

4. The information processing system according to claim 3, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on a time taken for sound to travel by bone conduction between the first acquisition means and the second acquisition means.

5. An information processing system as described in claim 2, further comprising a reference terminal different from the first acquisition means and the second acquisition means, wherein the distance calculation means calculates the distance between the first acquisition means and the second acquisition means based on the sound transmission time between the first acquisition means and the reference terminal and the sound transmission time between the second acquisition means and the reference terminal.

6. The information processing system of claim 2, wherein the distance calculation means calculates a distance traveled by at least one of the first acquisition means and the second acquisition means using an acceleration sensor provided in at least one of the first acquisition means and the second acquisition means, and calculates the distance between the first acquisition means and the second acquisition means based on the distance traveled.

7. The information processing system according to claim 2, wherein the distance calculation means detects the positions of the first acquisition means and the second acquisition means using a GPS (Global Positioning System) and calculates the distance between the first acquisition means and the second acquisition means based on the positions of the first acquisition means and the second acquisition means.

8. An information processing system comprising: a first acquisition means for acquiring a first echo reverberated at a first ear of a subject; a second acquisition means for acquiring a second echo reverberated at a second ear of the subject; an extraction means for extracting a first feature from the first echo and extracting the second feature from the second echo; and a determination means for determining whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

9. An information processing method comprising: acquiring a first feature based on a first echo sound that has echoed at a first ear of a target using a first acquisition means; acquiring a second feature based on a second echo sound that has echoed at a second ear of the target using a second acquisition means; and determining whether or not the target can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

10. A recording medium having recorded thereon a computer program for executing an information processing method, comprising: acquiring, by a first acquisition means, a first feature based on a first echo that has echoed at a first ear of a subject; acquiring, by a second acquisition means, a second feature based on a second echo that has echoed at a second ear of the subject; and determining whether or not the subject can be authenticated based on the first feature, the second feature, and the distance between the first acquisition means and the second acquisition means.

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