Human body communication apparatus and authentication method of the same

In one embodiment, a human body communication apparatus includes a first human body communication terminal carried by a person, a second human body communication terminal and an authentication unit included in the first or second human body communication terminal. The first human body communication terminal includes a first detection unit to detect first living body physiological information of the carrying person. The second human body communication terminal includes a human body contact sensor and a second detection unit to detect second living body physiological information of the person who touches the human body contact sensor. The authentication unit acquires the first and second living body physiological information and determines a correlation between the first and second living body physiological information to permit communication between the first and second human body communication terminals in accordance with the correlation.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-259764, filed on Nov. 22, 2010, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a human body communication apparatus and authentication method of the human body communication apparatus.

BACKGROUND

In a kind of human body communication that transmits/receives data by using a human body as a communication path, when a person carrying a human body communication mobile terminal touches a human body contact sensor provided in a human body communication terminal of the other party, data communication is performed between the human body communication mobile terminal and the human body communication terminal.

However, there is a case where data communication is performed between the human body communication mobile terminal and the human body communication terminal via another person touching the human body contact sensor even if the person himself carrying the human body communication mobile terminal has no intention to perform communication. Cases shown below, for example, are such a case.

When another person carrying no human body communication mobile terminal touches a human body contact sensor, data communication is performed between a human body communication mobile terminal and a human body communication terminal via the other person touching the human body contact sensor.

When another person carrying a human body communication mobile terminal touches a human body contact sensor, the human body communication mobile terminal of the other person touching the human body contact sensor is passed and data communication is performed between a human body communication mobile terminal of the person himself and a human body communication terminal via the other person.

Data communication not intended by the person himself carrying a human body communication mobile terminal could cause a security problem.

To ensure security, personal authentication data such as a fingerprint pattern is normally registered with a human body communication mobile terminal in advance and the identity of a person touching the human body contact sensor is authenticated by comparing with the fingerprint pattern of the person touching the human body contact sensor.

However, registering personal authentication data with a human body communication mobile terminal in advance could cause a problem in terms of personal information management. If a human body communication mobile terminal is lost, personal authentication data could be misused.

Thus, When a human body communication mobile terminal is shared by a plurality of persons, it becomes difficult to register personal authentication data with the human body communication mobile terminal in advance and therefore, instead of authenticating personal identification, a human body communication apparatus and an authentication method capable of authenticating a communication intention of the person himself carrying a human body communication mobile terminal are desired.

DETAILED DESCRIPTION

In one embodiment, a human body communication apparatus includes a first human body communication terminal carried by a person, a second human body communication terminal and an authentication unit included in the first or second human body communication terminal. The first human body communication terminal includes a first detection unit to detect first living body physiological information of the carrying person. The second human body communication terminal includes a human body contact sensor and a second detection unit to detect second living body physiological information of the person who touches the human body contact sensor. The authentication unit acquires the first and second living body physiological information and determines a correlation between the first and second living body physiological information to permit communication between the first and second human body communication terminals in accordance with the correlation.

Hereinafter, further embodiments will be described with reference to the drawings. In the drawings, same reference characters denote the same or similar portions.

A first embodiment will be described with reference toFIGS. 1 and 2.FIG. 1is a block diagram showing a human body communication apparatus of the first embodiment andFIG. 2is a figure for explaining the human body communication apparatus.

As shown inFIG. 1, a human body communication apparatus10of the first embodiment includes a mobile first human body communication terminal11carried by a person and a floor-mounted second human body communication terminal12installed in a predetermined location.

The first human body communication terminal11and the second human body communication terminal12perform data communication by transmitting/receiving a phase-modulated analog signal, for example, after a person13(hereinafter, referred to simply as a carrier13) carrying the first human body communication terminal11touches a human body contact sensor provided in the second human body communication terminal12by using the carrier13as a communication path. The frequency of the analog signal used for human body communication (human body communication signal) is substantially between 1 MHz and 10 MHz.

The first human body communication terminal11includes an analog front-end unit14to transmit/receive an analog signal, a signal processing unit15that processes a signal transmitted/received by the analog front-end unit14, and a first sensor16(first detection unit) to detect first living body physiological information of the carrier13.

The analog front-end unit14includes a receiving unit that receives an analog signal and a transmitting unit that transmits the analog signal.

The receiving unit includes a receiving electrode17that receives an analog signal by contact with the carrier13or electrostatic coupling via clothing, a low-noise amplifier18that amplifies the received analog signal, and an analog/digital converter (hereinafter, referred to as an AD converter)19that converts the amplified analog signal into a digital signal and outputs the digital signal to the signal processing unit15, for example.

The transmitting unit includes, a digital/analog converter (hereinafter, referred to as an DA converter)20that converts a digital signal from the signal processing unit15into an analog signal, a power amplifier21that amplifies the converted analog signal, and a transmitting electrode22that transmits the analog signal amplified by contact with the carrier13or electrostatic coupling via clothing, for example.

The signal processing unit15includes a CPU23that performs arithmetic processing, a RAM (random Access Memory)25that temporarily stores arithmetic processing results, and a ROM (Read Only Memory)24that stores programs of arithmetic processing procedures or the like, for example.

The second human body communication terminal12includes a human body contact sensor26that detects human body contact and a second sensor (second detection unit) to detect second living body physiological information of a person (hereinafter, referred to simply as a human body contactor) in contact with the human body contact sensor26in the form of being contained in the human body contact sensor26.

The second human body communication terminal12includes a signal processing unit28that processes the second living body physiological information from the second sensor27and, like the first human body communication terminal11, the analog front-end unit14to transmit/receive an analog signal and the signal processing unit15that processes a signal transmitted/received by the analog front-end unit14.

The first sensor16herein includes a function to amplify a detected signal and output a digital signal obtained by an AD conversion of the signal to the CPU23, which also applies to the second sensor27.

As shown inFIG. 2, the first sensor16is a sensor that detects a vibration, for example, caused by pulsation in the chest as first living body physiological information31of the carrier13and converts a continuous pulsation waveform in a fixed period into an electric signal.

The second sensor27is a sensor that detects a change in optical transmittance caused by a contact site pulsation at a fingertip, for example, as second living body physiological information32of a human body contactor and converts, like the first living body physiological information31, a continuous pulsation waveform in a fixed period into an electric signal.

The second human body communication terminal12is provided with an authentication unit (not shown) that, when a correlation between the first and second living body physiological information31,32is established after the first living body physiological information31is obtained from the first human body communication terminal11via a human body communication path33, the correlation between the first and second living body physiological information31,32is determined, permits communication between the first and second human body communication terminals11,12.

The authentication unit is embodied by the signal processing unit15, for example. The ROM24of the signal processing unit15has a program such as a procedure to determine a correlation between the first and second living body physiological information31,32and conditions necessary to determine and judge whether there is any correlation therebetween stored therein.

The CPU23performs arithmetic processing to determine the correlation between the first and second living body physiological information31,32according to the program stored in the ROM24. An arithmetic result is stored in the RAM25.

The above human body communication apparatus10is configured to verify that the carrier13is in contact with the human body contact sensor26, that is, the carrier13and the human body contactor are one and the same person to authenticate a communication intention of the carrier13.

Next, an authentication method of the communication intention of the carrier13will be described with reference toFIG. 3.FIG. 3is a diagram showing the authentication procedures of the human body communication apparatus.

The first human body communication terminal11is first in a standby state by operating the receiving unit ranging from the receiving electrode17to the AD converter19until some communication signal arrives after the carrier13touches the human body contact sensor26.

When human body contact with the human body contact sensor26is detected, the second human body communication terminal12transmits a human body contact detection signal (step S11).

When the human body contact detection signal is received, the first human body communication terminal11operates the transmitting unit ranging from the DA converter20to the transmitting electrode22to acquire the first living body physiological information31by transmitting a communication response signal indicating reception of a human body contact detection signal (step S12).

When the communication response signal is received, the second human body communication terminal12acquires the second living body physiological information32and requests transmission of the first living body physiological information31by transmitting an authentication request signal (step S13).

When the authentication request signal is received, the first human body communication terminal11transmits the first living body physiological information31(step S14).

When the first living body physiological information31is received, the second human body communication terminal12determines a correlation between the first living body physiological information31and the second living body physiological information32by a method described later to determine whether there is any correlation between the first living body physiological information31and the second living body physiological information32and, when there is a correlation therebetween, the second human body communication terminal12transmits a second authentication key to exchange authentication keys (step S15).

When the second authentication key is received, the first human body communication terminal11transmits a first authentication key (step S16).

When the first authentication key is received, the exchange of the authentication keys is completed and the second human body communication terminal12transmits a communication permission signal (step S17).

With the reception of the communication permission signal by the first human body communication terminal11, the authentication is completed. Hereinafter, data communication can freely be performed between the first and second human body communication terminals11,12through human body communication using the carrier13as a communication path.

On the other hand, if there is no correlation between the first living body physiological information31and the second living body physiological information32, the second human body communication terminal12transmits a notification signal to reject a connection and interrupts the communication. As a result, data communication cannot be performed between the first and second human body communication terminals11,12.

The correlation between the first living body physiological information31and the second living body physiological information32is determined by a method of searching for synchronization points of the first and second living body physiological information31,32, for example. The method is a method by which a point where the magnitude of waveform shifts at each sampling point is minimum as a whole is searched for, for example, a point where the sum of squares of differences between the first and second living body physiological information31,32is at the minimum by comparing both waveforms while gradually shifting the time axis.

Whether there is any correlation is determined based on the magnitude of waveform shifts. If the first and second living body physiological information31,32match perfectly, the magnitude of waveform shifts becomes 0.

In accordance with the method, waveforms without periodicity or waveforms whose period is long can be compared relatively accurately without picking up data for one period.

When there is any correlation between the first living body physiological information31and the second living body physiological information32, that the carrier13touches the human body contact sensor26, that is, that the carrier13and the human body contactor are one and the same person is verified so that the communication intention of the carrier13can be authenticated.

The correlation between the first living body physiological information31and the second living body physiological information32herein is not necessarily expressed as a function mathematically and means an index to judge how close a similarity there is between two waveforms at a level that does not cause any practical problem.

The first living body physiological information31transmitted from the first human body communication terminal11is real-time data read by the first sensor16, but if a signal waveform processing delay or the like is considered, the first living body physiological information31may be mismatched with the second living body physiological information32in a simple waveform comparison.

FIG. 4is a diagram showing a process flow of the first and second living body physiological information31,32read by the first and second sensors16,27. As shown inFIG. 4, it is necessary to acquire the first and second living body physiological information31,32in the same timing by the first and second sensors16,27to search for synchronization timing for a waveform comparison.

The timing to start acquisition of the first and second living body physiological information31,32is preferably a time when a person touches the human body contact sensor26and a communication response signal to a human body contact detection signal is output.

The first living body physiological information31acquired by the first human body communication terminal11side needs to be signal-converted and transmitted to the second human body communication terminal12side and thus, it is necessary to temporarily store the second living body physiological information32acquired by the second human body communication terminal12side.

A waveform comparison is made after the first and second living body physiological information31,32become complete on the second human body communication terminal12side, but noise mixing and differences in waveform of fine portions are present and therefore, it is desirable to use an error correction technique or the like for correlation output to make a more accurate judgment.

FIGS. 5 to 7are figures showing cases where there is no correlation between the first and second living body physiological information31,32, that is, the carrier13does not touch the human body contact sensor26and the carrier13and the human body contactor are different persons,FIGS. 5 and 6are figures showing cases where the human body contactor carries no first human body communication terminal, andFIG. 7is a figure showing a case where the human body contactor carries the first human body communication terminal.

Assume as shown inFIG. 5that a person40(hereinafter, referred to simply as non-carrier40) carrying no first communication terminal11and the carrier13are a parent and child hand in hand together. If the non-carrier40casually touches the human body contact sensor26when passing by the side of the second human body communication terminal12, a human body communication path41reaching the carrier13is formed via the non-carrier40(human body contactor40).

In this case, there is no correlation between the first living body physiological information31and the second living body physiological information32and thus, the communication intension of the carrier13is not authenticated. Therefore, unintended data communication of the carrier13can be prevented.

Assume as shown inFIG. 6that a non-carrier45pushes in between the second human body communication terminal12and the carrier13when the carrier13stands by the side of the second human body communication terminal12. If one hand of the non-carrier45casually touches the human body contact sensor26and the other hand comes into contact with the carrier13when the non-carrier45slips between the second human body communication terminal12and the carrier13, a human body communication path46reaching the carrier13is formed via the non-carrier45(human body contactor45).

Also in this case, there is no correlation between the first living body physiological information31and the second living body physiological information32and thus, the communication intension of the carrier13is not authenticated. Therefore, unintended data communication of the carrier13can be prevented.

Assume as shown inFIG. 7that a person50(hereinafter, referred to simply as a carrier50) carrying the same first human body communication terminal11pushes in between the second human body communication terminal12and the carrier13when the carrier13stands by the side of the second human body communication terminal12and touches the human body contact sensor26while coming into contact with the carrier13.

If the side of the carrier50is accidentally closed, a human body communication path51reaching the carrier13by passing through the lower arm and waist of the carrier50(human body contactor50) may be formed without a communication path reaching the first human body communication terminal11carried by the carrier50via the upper arm and chest of the carrier50being formed.

Also in this case, there is no correlation between the first living body physiological information31and the second living body physiological information32and thus, the communication intension of the carrier13is not authenticated. Therefore, unintended data communication of the carrier13can be prevented.

In the first embodiment, as described above, the first human body communication terminal11includes the first sensor16that detects the first living body physiological information31of the carrier13, the second human body communication terminal12includes the second sensor27that detects the second living body physiological information32of a human body contactor, and an authentication unit checks whether there is any correlation between the first and second living body physiological information31,32.

As a result, when there is a correlation between the first and second living body physiological information31,32, that the carrier13and the human body contactor are one and the same person is verified so that data communication is performed only if the carrier13has a communication intention. Therefore, the human body communication apparatus capable of authenticating the communication intention of the person himself carrying a human body communication terminal and the authentication method of the human body communication apparatus are obtained.

Data communication not intended by the person himself carrying a first human body communication terminal is prevented so that security problems are prevented from occurring.

While a case where a correlation between the first and second living body physiological information31,32is determined by the second human body communication terminal12is described here, the determination may be made by the first human body communication terminal11.FIG. 8is a diagram showing an authentication procedure when a correlation between the first and second living body physiological information31,32is determined by the first human body communication terminal11.

As shown inFIG. 8, steps S11and S12are the same as the case where the correlation between the first and second living body physiological information31,32is determined by the second human body communication terminal12.

When a communication response signal is received, the second human body communication terminal12acquires the second living body physiological information32and transmits the acquired second living body physiological information32(step S21).

When the second living body physiological information32is received, the first human body communication terminal11determines a correlation between the first living body physiological information31and the second living body physiological information32, judges whether there is any correlation between the first living body physiological information31and the second living body physiological information32, and, if there is a correlation, transmits a first authentication key to exchange authentication keys (step S22).

When the first authentication key is received, the second human body communication terminal12transmits a second authentication key (step S23).

When the second authentication key is received, the exchange of the authentication keys is completed and the first human body communication terminal11transmits a communication permission signal (step S24).

With the reception of the communication permission signal by the second human body communication terminal12, the authentication is completed. Hereinafter, data communication can freely be performed between the first and second human body communication terminals11,12through human body communication using the carrier13as a communication path.

On the other hand, if there is no correlation between the first living body physiological information31and the second living body physiological information32, the first human body communication terminal11transmits a notification signal to reject a connection and interrupts the communication.

While a case where the contact site is the fingertip is described here, a palm may be sufficient as a contact site. In the case of the palm, it is possible that the palm is in contact with the second sensor27or is put above the second sensor27.

A second embodiment will be described with reference toFIG. 9.FIG. 9is a figure for explaining a human body communication apparatus of the second embodiment. In the second embodiment, the same reference numerals are attached to the same structural elements as those in the first embodiment to omit a description of such structural elements and only different portions will be described.

The difference of the second embodiment from the first embodiment is that first and second living body physiological information is assumed to be fluctuations of the center of gravity of a human body. While a human body stands upright, the center of gravity continually fluctuates. If such fluctuations can be detected, the fluctuations can be used as the first and second living body physiological information.

As shown inFIG. 9, in a human body communication apparatus of the second embodiment, the first human body communication terminal11contains, as a first sensor (first detection unit)61, an acceleration sensor to detect fluctuations of a human body, for example, a MEMS (Micro Electro Mechanical Systems) three-axis acceleration sensor.

The second human body communication terminal12has, as a second sensor (second detection unit)62, a sensor mat to read a movement locus of the center of gravity of a human body, for example, a pressure sensitive position sensor externally attached thereto.

Since the orientation in which the terminal is carried cannot be in a fixed direction with respect to the ground, the first sensor61determines the direction of gravity simultaneously with movement of the center of gravity. When the direction of gravity is determined, the first sensor61acquires first living body physiological information63by cutting out only components parallel to the gravity.

The second sensor62is laid on the floor where the second human body communication terminal12is installed. For example, the carrier13instantaneously stops to try to touch the human body contact sensor26. The first sensor61detects the first living body physiological information63and the second sensor62detects second living body physiological information64from fluctuations of the center of gravity of the carrier13while the carrier13stops.

In this case, there is a correlation between the first living body physiological information63and the second living body physiological information64and thus, that the carrier13touches the human body contact sensor26, that is, that the carrier13and the human body contactor are one and the same person is verified so that the communication intention of the carrier13can be authenticated.

On the other hand, in situations shown inFIGS. 5 to 7, there is no correlation between the first living body physiological information63of the carrier13and the second living body physiological information of the human body contactor, the communication intension of the carrier13is not authenticated. Therefore, unintended data communication of the carrier13can be prevented.

In the second embodiment, as described above, fluctuations of the center of gravity of a human body are adopted as the first and second living body physiological information63,64. Accordingly, the second embodiment can advantageously be applied when it is difficult to apply the method of detecting living body physiological information of a human body, for example, when it is difficult for the first human body communication terminal to feel the vibration of pulsation.

When a mobile device containing an acceleration sensor in advance is modified as a first human body communication terminal, an advantage that no new sensor to detect the vibration due to pulsation of the chest needs to be provided is also obtained.

A third embodiment will be described with reference toFIG. 10.FIG. 10is a figure for explaining a human body communication apparatus of the third embodiment. In the third embodiment, the same reference numerals are attached to the same structural elements as those in the first embodiment to omit a description of such structural elements and only different portions will be described. The third embodiment is different from the first embodiment in that the first human body communication terminal is a type that can be mounted on a wrist.

As shown inFIG. 10, in a human body communication apparatus of the third embodiment, a first human body communication terminal71is a type of human body communication terminal that can be mounted on a wrist. The first human body communication terminal71contains a first sensor (not shown) that detects pulsation of a wrist.

The first sensor detects first living body physiological information73based on pulsation of a person72(hereinafter, referred to simply as a carrier72) carrying the first human body communication terminal71. The first human body communication terminal71transmits the first living body physiological information73to the second human body communication terminal12via a human body communication path74.

In this case, there is a correlation between the first living body physiological information73and the second living body physiological information32and thus, that the carrier72touches the human body contact sensor26, that is, that the carrier72and the human body contactor are one and the same person is verified so that the communication intention of the carrier72can be authenticated.

On the other hand, in situations shown inFIGS. 5 to 7, there is no correlation between the first living body physiological information73of the carrier72and the second living body physiological information of the human body contactor, the communication intension of the carrier72is not authenticated. Therefore, unintended data communication of the carrier72can be prevented.

Since the artery passes through the wrist near the surface of a human body, detection of the pulsation is reliable and easy. In the first human body communication terminal11shown inFIG. 2, detection of the pulsation may be inaccurate depending on the mounting site of a human body.

If the first human body communication terminal11is mounted on the chest relatively close to the heart, for example, it is easy to detect the vibration caused by pulsation of a body, but if the first human body communication terminal11is mounted on a site where it is difficult to feel the vibration caused by a pulse such as the abdomen, it becomes difficult to accurately detect pulsation.

In the third embodiment, as described above, the first human body communication terminal71is of the type to mount on a wrist. Accordingly, an advantage is obtained in that malfunctioning of being incapable of acquiring first living-body-physiological information depending on the mounting site of the first communication terminal11is improved.

Further, when compared with the first communication terminal11, advantages such as being easy to bring the first human body communication terminal71into direct contact with a human body and being easy to mount the first human body communication terminal71are obtained.

A fourth embodiment will be described with reference toFIG. 11.FIG. 11is a figure for explaining a human body communication apparatus of the fourth embodiment. In the fourth embodiment, the same reference numerals are attached to the same structural elements as those in the first embodiment to omit a description of such structural elements and only different portions will be described. The fourth embodiment is different from the first embodiment in that a first sensor is externally attached to a first human body communication terminal.

As shown inFIG. 11, in a human body communication apparatus of the fourth embodiment, a first sensor81to detect pulsation of a wrist is externally attached to the first human body communication terminal11. The first sensor81is mounted on a wrist of the carrier13. Communication authentication is provided (paired) to the first human body communication terminal11and the first sensor81in advance.

The first sensor81detects first living body physiological information82based on pulsation of the wrist and transmits the first living body physiological information82to the first human body communication terminal11via a human body communication path83. The first human body communication terminal11transmits the first living body physiological information82to the second human body communication terminal12via the human body communication path33.

The first sensor81is provided near the second sensor27and thus, noise mixed in the first living body physiological information82detected by the first sensor81from a wrist and the second living body physiological information32detected by the second sensor27from a fingertip and differences in waveform of fine portions are reduced. As a result, it is expected to increase a correlation between the first and second living body physiological information82,32.

In this case, there is a correlation between the first and second living body physiological information82,32and thus, it is verified that the carrier13touches the human body contact sensor26, that is, it is verified that the carrier13and the human body contactor are one and the same person. It is possible to authenticate the communication intention of the carrier13.

On the other hand, in situations shown inFIGS. 5 to 7, there is no correlation between the first living body physiological information82of the carrier13and the second living body physiological information of the human body contactor, the communication intension of the carrier13is not authenticated. Therefore, it is possible to prevent unintended data communication of the carrier13.

In the fourth embodiment, as described above, the first sensor81is externally attached to the first human body communication terminal11. As a result, an advantage is obtained in that the first sensor81can be mounted at a site most appropriate to detect the first living body physiological information82.

A fifth embodiment will be described with reference toFIG. 12.FIG. 12is a figure for explaining a human body communication apparatus of according to the fifth embodiment. In the fifth embodiment, the same reference numerals are attached to the same structural elements as those in the first embodiment to omit a description of such structural elements and only different portions will be described. The fifth embodiment is different from the first embodiment in that a second sensor is externally attached to a second human body communication terminal.

As shown inFIG. 12, in a human body communication apparatus of the fifth embodiment, a second sensor91to detect pulsation of a wrist is externally attached to the second human body communication terminal12. The second sensor91is mounted on a wrist of a human body contactor, here, the carrier13.

The second sensor91detects second living body physiological information92based on pulsation of the wrist and transmits the second living body physiological information92to the second human body communication terminal12via a human body communication path93.

The second sensor91has a structure similar to an arm-in type sphygmomanometer, for example, and when an arm is passed through an arm cylinder whose inner side is movable and brought into contact with the human body contact sensor26, an air bag of the arm cylinder is automatically swollen so that the second sensor91is closely mounted on the wrist.

When the second living body physiological information92is detected, the air bag of the arm cylinder is automatically contracted so that the second sensor91is unmounted. Though it takes time to mount/unmount the second sensor91, mounting/unmounting is automatic so that a human body contactor is less likely to undergo stress.

The second living body physiological information92detected by the second sensor91from a wrist is more reliable than second living body physiological information detected from a fingertip and it is expected to increase a correlation between the first and second living body physiological information31,92.

In this case, there is a correlation between the first living body physiological information31and the second living body physiological information92and thus, it is verified that the carrier13touches the human body contact sensor26, that is, it is verified that the carrier13and the human body contactor are one and the same person. It is possible to authenticate the communication intention of the carrier13.

On the other hand, in situations shown inFIGS. 5 to 7, there is no correlation between the first living body physiological information31of the carrier13and the second living body physiological information92of the human body contactor, and the communication intension of the carrier13is not authenticated. Therefore, it is possible to prevent unintended data communication of the carrier13.

In the fifth embodiment, as described above, the second sensor91is externally attached to the second human body communication terminal12. As a result, an advantage is obtained in that the second living body physiological information92can be detected from a wrist which is more reliable than a fingertip.

A sixth embodiment will be described with reference toFIGS. 13 and 14.FIG. 13is a figure for explaining a human body communication apparatus of the sixth embodiment andFIG. 14is a block diagram showing the human body communication apparatus. In the sixth embodiment, the same reference numerals are attached to the same structural elements as those in the first embodiment to omit a description of such structural elements and only different portions will be described. The sixth embodiment is different from the first embodiment in that an electric signal emitted owing to a living body physiological activity of a human body is adopted as living body physiological information.

To begin with, an electric signal emitted owing to a living body physiological activity of a human body (referred to as a living body physiological activity electric signal), for example, an electric signal caused by a neural activity, an electric signal due to changes in human body resistance caused by the flow of blood/lymph, and an electric signal generated by changes of interaction with an external electric field or electromagnetic field flows in the human body. The living body physiological activity electric signal is different depending on an active state of a human body and thus can be used as an authentication signal to identify the human body.

As shown inFIG. 13, a living body physiological activity electric signal101is distributed substantially in the range of 1 kHz to 1 MHz. On the other hand, a human body communication signal102is distributed substantially in a frequency band of 1 MHz to 10 MHz and thus, the living body physiological activity electric signal101and the human body communication signal102will not interfere with each other.

Therefore, the living body physiological activity electric signal101is selected from human body electric signals containing the living body physiological activity electric signal101and the human body communication signal102, the living body physiological activity electric signal101can be used as first and second living body physiological information.

As shown inFIG. 14, in a human body communication apparatus110, a first human body communication terminal111is provided with a first detection unit112to select the living body physiological activity electric signal101from human body electric signals.

In the first human body communication terminal111, a human body electric signal received by the receiving electrode17is amplified by the low-noise amplifier18. The amplified human body electric signal is input into the AD converter19and the first detection unit112.

In the first detection unit112, a low-pass filter (select circuit)113allows only the living body physiological activity electric signal101from the human body electric signal amplified by the low-noise amplifier18to pass.

An amplifier114amplifies the living body physiological activity electric signal101that has passed through the low-pass filter113. The amplification is intended to compensate for insertion losses of the low-pass filter113. An AD converter115converts the amplified living body physiological activity electric signal101into a digital signal and outputs the digital signal to the CPU23of the signal processing unit15.

Similarly, a second human body communication terminal (not shown) is provided with a second detection unit to select the living body physiological activity electric signal101from a human body electric signal of a human body contactor. The configuration of the second detection unit is the same as that of the first detection unit and thus, a description of the second detection unit is omitted.

The living body physiological activity electric signal101is selected when first and second living body physiological information is acquired by following the flow shown inFIG. 3. The selected living body physiological activity electric signal101is AD-converted and fetched by the CPU23as a digital signal for processing.

The first detection unit112of the first human body communication terminal111selects the living body physiological activity electric signal101of the carrier13. The second detection unit of the second human body communication terminal selects the living body physiological activity electric signal101of the carrier13.

In this case, there is a correlation between the first living body physiological information and the second living body physiological information and thus, that the carrier13touches the human body contact sensor26, that is, that the carrier13and the human body contactor are one and the same person is verified so that the communication intention of the carrier13can be authenticated.

On the other hand, in situations shown inFIGS. 5 to 7, there is no correlation between the first living body physiological information31of the carrier13and the second living body physiological information of the human body contactor, the communication intension of the carrier13is not authenticated. Therefore, it is possible to prevent unintended data communication of the carrier13.

The human body communication apparatus110uses the living body physiological activity electric signal101emitted owing to a living body physiological activity of a human body and thus, the first sensor16and the second sensor27shown in the first embodiment are not needed.

In the sixth embodiment, as described above, the living body physiological activity electric signal101is used as the first and second living body physiological information and thus, the first and second sensors are not needed. The first detection unit112can be formed integrally in the analog front-end unit14or the signal processing unit15as a chip and thus, an advantage is obtained in that the first and second human body communication terminals can be simplified and miniaturized.