Identification signal checking apparatus and methods

0001The present invention relates to identification signal checking apparatus and methods, such as those suitable for use in a keyless entry system.

0002A keyless entry system has been proposed. In this keyless entry system, infrared rays or radio waves are used to transmit an identification signal from a key apparatus side to a lock apparatus side for the locking or the unlocking thereof.

0003Such keyless entry system employs a one-way communication in which the key apparatus side constantly transmits the same identification signal. Therefore, when this communication is intercepted, the identification signal may disadvantageously be stolen easily.

0004Particularly when the identification signal is transmitted by using the infrared rays, it is possible to copy the identification signal easily by a so-called learning remote controller, which has already been developed into a social problem.

0005Moreover, since in the above keyless entry system it is possible to detect a specific identification signal by using each of various identification signals to detect whether or not the identification signal coincides with the specific identification signal, there is the critical disadvantage in security.

0006Therefore, a keyless entry system has been proposed in which a portable apparatus (key apparatus) transmits an encryption value to a main apparatus (lock apparatus) and the main apparatus determines whether or not an encryption value which it obtains by itself by calculation of a value signal coincides with the received encryption value (see Japanese laid-open patent publication No. 7-269196 and Japanese laid-open patent publication No. 7-274258).

0007In such proposed keyless entry system, since the main apparatus determines whether or not the encryption value which it obtains by itself by calculation of the value signal coincides with the received encryption value, the security is improved.

0008However, in the previously proposed keyless entry system with a satisfactory security, since the main apparatus determines whether or not the encryption value which it obtains by itself by calculation of the value signal coincides with the received encryption value, except when the portable apparatus (key apparatus) and the main apparatus (lock apparatus) are manufactured, it is impossible that, after the portable apparatus and the main apparatus are manufactured, a specific identification signal is registered in both of the key apparatus and the main apparatus by transmitting the same specific identification signal from the portable apparatus to the main apparatus.

0009Therefore, in such system, when the portable apparatus (key apparatus) and the main apparatus (lock apparatus) are manufactured, the same specific identification signal is registered in both of them. Therefore, it is necessary to manage both of the portable apparatus (key apparatus) and the main apparatus (lock apparatus) as a pair of objects to be managed until the lock apparatus is finally built in a door, for example. This necessity leads to the disadvantage in effective management and in physical distribution.

0010In view of such aspects, it is therefore an aim of the present invention to improve the security with a comparatively simple arrangement and to make it unnecessary to manage the key apparatus (apparatus to be detected) and the lock apparatus (detecting apparatus) as a pair of separate items to be managed.

0011According to an aspect of the present invention, an identification signal checking apparatus includes an apparatus to be detected having a first wireless transmitting and receiving unit, a first signal processing unit and a first memory unit for storing an identification signal and includes a detecting apparatus having a second wireless transmitting and receiving unit, a second signal processing unit, a second memory unit for storing an identification signal, and a communication permission signal generating means. When the detecting apparatus receives a response request signal from the apparatus to be detected, the detecting apparatus transmits a random number signal obtained from the random number generating unit. When receiving the random number signal, the apparatus to be detected encrypts said identification signal stored in the first memory unit by using the random number signal and transmits the encrypted identification signal to the detecting apparatus. The detecting apparatus decrypts the encrypted identification signal and checks whether or not the decrypted identification signal coincides with the identification signal stored in the second memory unit.

0012According to the present invention, the detecting (lock apparatus) transmits the random number signal and the apparatus to be detected (key apparatus) encrypts the identification signal by using the random number signal and transmits it to the detecting apparatus. Therefore, since the identification signal transmitted from the apparatus to be detected to the detecting apparatus is the encrypted signal obtained by encryption employing the random number signal and hence is always an unique signal, the security is improved.

0013According to the present invention, since the detecting apparatus decrypts the encrypted identification signal, even if the apparatus to be detected and the detecting apparatus are separately manufactured and distributed on the market, when the detecting apparatus is built in a door or the like, the detecting apparatus (lock apparatus) decrypts the encrypted signal transmitted from the apparatus to be detected (key apparatus) to obtain the specific identification signal. If the identification signal obtained by decryption is registered in the detecting apparatus, then it is possible to register the same identification signal in both of the apparatus to be detected (key apparatus) and the detecting apparatus (lock apparatus) .

0014The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: <ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a block diagram showing an arrangement of an identification signal checking apparatus according to a first embodiment of the present invention;</li><li>FIG. 2 is a flowchart used to explain an operation of the identification signal checking apparatus according to the first embodiment of the present invention;</li><li>FIGS. 3A to 3D are timing charts used to explain communication between a key apparatus and a lock apparatus according to the first embodiment of the present invention;</li><li>FIG. 4 is a block diagram showing an arrangement of an identification signal checking apparatus according to a second embodiment of the present invention;</li><li>FIG. 5 is a flowchart used to explain an operation of the identification signal checking apparatus according to the second embodiment of the present invention;</li><li>FIG. 6 is a block diagram showing an arrangement of an identification signal checking apparatus according to a third embodiment of the present invention; and</li><li>FIG. 7 is a flowchart used to explain an operation of the identification signal checking apparatus according to the third embodiment of the present invention.</li></ul>

0015An identification signal checking apparatus and an identification signal checking method according to a first embodiment of the present invention will be described with reference to the accompanying drawings. In this embodiment, the identification signal checking apparatus and method are applied to a keyless entry system for opening and closing a door.

0016As shown in FIG. 1, a portable key apparatus 1 (an apparatus to be detected) has a switch unit 2 for issuing commands to open and close a door, a signal processing circuit unit 3, an infrared-ray transmitting and receiving unit 4 for communicating with a lock apparatus 10 described later on, and a memory unit 5 for storing a specific (own) identification signal ID.

0017The signal processing circuit unit 3 is formed of a microcomputer. When the switch unit 2 issues a commend to open or close the door by operating a switch thereof, the signal processing circuit unit 3 generates a response request signal including a lock/unlock command signal and supplies this response request signal to the infrared-ray transmitting and receiving unit 4. The infrared-ray transmitting and receiving unit 4 transmits the response request signal to the lock apparatus 10.

0018When the key apparatus 1 receives a random number signal X formed of 24 bits, for example, from the lock apparatus 10, the signal processing circuit unit 3 encrypts a specific identification signal ID of 24 bits, for example, stored in the memory unit 5 to convert it into a code signal of 24 bits, for example, in accordance with a predetermined function f(X, ID) by using the 24-bit random number signal X, for example. Then, the signal processing circuit unit 3 transmits the encrypted signal f(X, ID) to the lock apparatus 10.

0019This function f(X, ID) is defined as shown below, for example, such that if respective corresponding bits of the random number signal X and the identification signal ID have the same value of "1" or "0", then the value of a corresponding bit in the function f(X, ID) is set to "1" and if the respective corresponding bits have the values different from each other, then the value thereof in the function f(X, ID) is set to "0". <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="25" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="6.30mm" /><colspec colnum="2" colname="col2" colwidth="6.30mm" /><colspec colnum="3" colname="col3" colwidth="6.30mm" /><colspec colnum="4" colname="col4" colwidth="6.30mm" /><colspec colnum="5" colname="col5" colwidth="6.30mm" /><colspec colnum="6" colname="col6" colwidth="6.30mm" /><colspec colnum="7" colname="col7" colwidth="6.30mm" /><colspec colnum="8" colname="col8" colwidth="6.30mm" /><colspec colnum="9" colname="col9" colwidth="6.30mm" /><colspec colnum="10" colname="col10" colwidth="6.30mm" /><colspec colnum="11" colname="col11" colwidth="6.30mm" /><colspec colnum="12" colname="col12" colwidth="6.30mm" /><colspec colnum="13" colname="col13" colwidth="6.30mm" /><colspec colnum="14" colname="col14" colwidth="6.30mm" /><colspec colnum="15" colname="col15" colwidth="6.30mm" /><colspec colnum="16" colname="col16" colwidth="6.30mm" /><colspec colnum="17" colname="col17" colwidth="6.30mm" /><colspec colnum="18" colname="col18" colwidth="6.30mm" /><colspec colnum="19" colname="col19" colwidth="6.30mm" /><colspec colnum="20" colname="col20" colwidth="6.30mm" /><colspec colnum="21" colname="col21" colwidth="6.30mm" /><colspec colnum="22" colname="col22" colwidth="6.30mm" /><colspec colnum="23" colname="col23" colwidth="6.30mm" /><colspec colnum="24" colname="col24" colwidth="6.30mm" /><colspec colnum="25" colname="col25" colwidth="6.30mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">ID</entry><entry namest="col2" nameend="col2" align="center">0</entry><entry namest="col3" nameend="col3" align="center">1</entry><entry namest="col4" nameend="col4" align="center">0</entry><entry namest="col5" nameend="col5" align="center">1</entry><entry namest="col6" nameend="col6" align="center">0</entry><entry namest="col7" nameend="col7" align="center">1</entry><entry namest="col8" nameend="col8" align="center">0</entry><entry namest="col9" nameend="col9" align="center">1</entry><entry namest="col10" nameend="col10" align="center">0</entry><entry namest="col11" nameend="col11" align="center">1</entry><entry namest="col12" nameend="col12" align="center">0</entry><entry namest="col13" nameend="col13" align="center">1</entry><entry namest="col14" nameend="col14" align="center">0</entry><entry namest="col15" nameend="col15" align="center">1</entry><entry namest="col16" nameend="col16" align="center">0</entry><entry namest="col17" nameend="col17" align="center">1</entry><entry namest="col18" nameend="col18" align="center">0</entry><entry namest="col19" nameend="col19" align="center">1</entry><entry namest="col20" nameend="col20" align="center">0</entry><entry namest="col21" nameend="col21" align="center">1</entry><entry namest="col22" nameend="col22" align="center">0</entry><entry namest="col23" nameend="col23" align="center">1</entry><entry namest="col24" nameend="col24" align="center">0</entry><entry namest="col25" nameend="col25" align="center">1</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">X</entry><entry namest="col2" nameend="col2" align="center">1</entry><entry namest="col3" nameend="col3" align="center">1</entry><entry namest="col4" nameend="col4" align="center">0</entry><entry namest="col5" nameend="col5" align="center">1</entry><entry namest="col6" nameend="col6" align="center">1</entry><entry namest="col7" nameend="col7" align="center">1</entry><entry namest="col8" nameend="col8" align="center">0</entry><entry namest="col9" nameend="col9" align="center">1</entry><entry namest="col10" nameend="col10" align="center">1</entry><entry namest="col11" nameend="col11" align="center">1</entry><entry namest="col12" nameend="col12" align="center">0</entry><entry namest="col13" nameend="col13" align="center">1</entry><entry namest="col14" nameend="col14" align="center">1</entry><entry namest="col15" nameend="col15" align="center">1</entry><entry namest="col16" nameend="col16" align="center">0</entry><entry namest="col17" nameend="col17" align="center">1</entry><entry namest="col18" nameend="col18" align="center">1</entry><entry namest="col19" nameend="col19" align="center">1</entry><entry namest="col20" nameend="col20" align="center">0</entry><entry namest="col21" nameend="col21" align="center">1</entry><entry namest="col22" nameend="col22" align="center">1</entry><entry namest="col23" nameend="col23" align="center">1</entry><entry namest="col24" nameend="col24" align="center">0</entry><entry namest="col25" nameend="col25" align="center">1</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">f(X, ID)</entry><entry namest="col2" nameend="col2" align="center">0</entry><entry namest="col3" nameend="col3" align="center">1</entry><entry namest="col4" nameend="col4" align="center">1</entry><entry namest="col5" nameend="col5" align="center">1</entry><entry namest="col6" nameend="col6" align="center">0</entry><entry namest="col7" nameend="col7" align="center">1</entry><entry namest="col8" nameend="col8" align="center">1</entry><entry namest="col9" nameend="col9" align="center">1</entry><entry namest="col10" nameend="col10" align="center">0</entry><entry namest="col11" nameend="col11" align="center">1</entry><entry namest="col12" nameend="col12" align="center">1</entry><entry namest="col13" nameend="col13" align="center">1</entry><entry namest="col14" nameend="col14" align="center">0</entry><entry namest="col15" nameend="col15" align="center">1</entry><entry namest="col16" nameend="col16" align="center">1</entry><entry namest="col17" nameend="col17" align="center">1</entry><entry namest="col18" nameend="col18" align="center">0</entry><entry namest="col19" nameend="col19" align="center">1</entry><entry namest="col20" nameend="col20" align="center">1</entry><entry namest="col21" nameend="col21" align="center">1</entry><entry namest="col22" nameend="col22" align="center">0</entry><entry namest="col23" nameend="col23" align="center">1</entry><entry namest="col24" nameend="col24" align="center">1</entry><entry namest="col25" nameend="col25" align="center">1</entry></row></tbody></tgroup></table></tables>

0020The infrared-ray transmitting and receiving unit 4 according to this embodiment is arranged so as to carry out communication in accordance with a known base band system. The base band system permits high-speed communication at a lower consumed power and simplifies a circuit arrangement as compared with other modulation systems such as an amplitude shift keying (ASK), a frequency shift keying (FSK) or the like.

0021The lock apparatus 10 is provided at a predetermined position in association with the door. The lock apparatus 10 has an infrared-ray transmitting and receiving unit 11 for communicating with the key apparatus 1, a signal processing circuit unit 12, a memory unit 13 for storing a specific (own) identification signal ID, a random number generating unit 14 for generating the random number signal X, and a drive unit 15 for controlling a door locking or unlocking operation based on a command signal from the signal processing circuit unit 12.

0022A binary counter for processing 24 bits, for example, is employed as the random number generating unit 14. This 24-bit binary counter carries out a count operation in accordance with a predetermined clock signal regardless of the communication. When the lock apparatus 10 receives the response request signal from the key apparatus 1, the operation of the 24-bit binary counter is stopped and then a count value of the binary counter at this time is read, thereby the 24-bit random number signal X, for example, being obtained.

0023The signal processing circuit unit 12 is formed of a microcomputer. When the lock apparatus 10 receives the response request signal from the key apparatus 1, the signal processing circuit unit 12 transmits the random number signal X generated by the random number generating unit 14 from the lock apparatus 10 to the key apparatus 1.

0024When the lock apparatus 10 receives from the key apparatus 1 the encrypted signal f(X, ID) obtained by encrypting the identification signal ID with the random number signal X, the signal processing circuit unit 12 decrypts the received encrypted signal f(X, ID) in accordance with a predetermined function f^-1{f(x, ID), X} by using the previously transmitted 24-bit random number signal X, for example, and checks whether or not the identification signal ID obtained by this decryption coincides with the specific (own) identification signal ID previously stored (registered) in the memory unit 13.

0025As a result of the check processing, if the decrypted identification signal ID coincides with the identification signal ID previously stored (registered), then the signal processing circuit unit 12 supplies a locking/unlocking command signal based on a door opening/closing command included in the response request signal to the drive unit 15. Then, under the operation of the drive unit 15, the door is opened or closed.

0026The infrared-ray transmitting and receiving unit 11 according to this embodiment is arranged similarly to the above-mentioned infrared-ray transmitting and receiving unit 4, and arranged so as to carry out communication in accordance with the known base band system. In FIG. 1, batteries 6 and 16 are used for energizing the key apparatus 1 and the lock apparatus 10, respectively.

0027An operation of the keyless entry system for opening and closing a door according to this embodiment will be described with reference to FIG. 2 which is a flowchart therefor and with reference to FIGS. 3A to 3D which are timing charts therefor. In this embodiment, it is assumed that the same specific (own) identification signals ID, e.g., the identification signals ID formed of codes of 24 bits, for example, are previously registered (stored) in the memory units 5 and 13.

0028In step S1 of the flowchart shown in FIG. 2, the switch unit 2 of the key apparatus 1 is operated and the switch thereof is set in its on-state, thereby a command to open or close a door being issued. In step S2, as shown in FIG. 3A, for example, the key apparatus 1 transmits the response request signal including the door opening/closing command signal to the lock apparatus 10 for a period of 100 ms. Then, the processing proceeds to step S3.

0029In step S3, the lock apparatus 10 receives the response request signal as shown in FIG. 3D. Then, the processing proceeds to step S4, wherein the lock apparatus 10 obtains the 24-bit random number signal X, for example, generated by the random number generating unit 14. In step S5, as shown in FIG. 3C, the lock apparatus 10 transmits the random number signal X to the key apparatus 1 for a period of 30 ms. Then, the processing proceeds to step S6.

0030In step S6, the key apparatus 1 receives the random number signal X as shown in FIG. 3B. Then, the processing proceeds to step S7, wherein the key apparatus 1 encrypts the specific (own) identification signal ID registered in the memory unit 5 to convert it into the 24-bit code signal, in accordance with the predetermined function f(X, ID) by using the 24-bit random number signal X, for example, and obtains the encrypted signal f(X, ID). Then, the processing proceeds to step S8, wherein the key apparatus 1 transmits the encrypted signal f(X, ID) to the lock apparatus 10 during the period of 30 ms, for example, as shown in FIG. 3A. Then, the processing proceeds to step S9.

0031In step S9, the lock apparatus 10 receives the encrypted signal f(X, ID) as shown in FIG. 3D. Then, the processing proceeds to step S10, wherein the lock apparatus 10 decrypts the received encrypted signal f(X, ID) in accordance with the predetermined function f^-1{f(x, ID), X} by using the previously transmitted random number signal X. Then, the processing proceeds to step S11, wherein the lock apparatus 10 checks whether or not the decrypted identification signal ID coincides with the specific (own) identification signal ID previously registered in the memory unit 13. In step S12, as a result of the check processing, if the decrypted identification signal ID coincides with the specific (own) identification signal ID previously registered (stored) in the memory unit 13, then, in accordance with the door opening or closing command signal of the response request signal, the signal processing circuit unit 12 supplies the unlocking or locking command signal to the drive unit 15 for carrying out the unlocking or locking operation of the door. Then, under the control of the drive unit 15, the door is opened or closed.

0032According to this embodiment, every time when the operation of opening or closing the door is attempted, the lock apparatus 10 generates the random number signal X and the key apparatus 1 encrypts the identification signal ID by using the random number signal X and transmits the encrypted signal f(X, ID) to the lock apparatus 10. Therefore, since the signals transmitted in this both-way communication are constantly different from each other, even if these communication signals are intercepted, the specific (own) identification signal ID is prevented from being stolen.

0033According to this embodiment, even if the operation of opening or closing the door is attempted any times, the possibility that the code signals coincide with each other by accident is constant, e.g., the possibility is constantly about one over 16.7 million in a case of the 24-bit code signal. Therefore, it is advantageously possible to realize the extremely high security with ease.

0034Since the lock apparatus 10 decrypts the encrypted identification signal f(X, ID), even if the key apparatus 1 and the lock apparatus 10 are separately manufactured and distributed on a market, when the lock apparatus 10 is built in a door or the like, the lock apparatus 10 decrypts the encrypted signal f(X, ID) transmitted from the key apparatus 1 to obtain the specific (own) identification signal ID. Therefore, if the identification signal ID obtained by decryption is registered in the memory unit 13 of the lock apparatus 10, then it is possible to register the same identification signal ID in both of the key apparatus 1 and the lock apparatus 10.

0035Therefore, according to the first embodiment, it is not necessary to manage both of the key apparatus 1 and the lock apparatus 10 as a pair of the objects to be managed, which leads to the advantages in effective management and physical distribution.

0036An identification signal checking apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. In FIG. 4, parts corresponding to those in FIG. 1 are marked with the same reference numerals and hence need not be described.

0037In the second embodiment, a nonvolatile memory unit 5 of a key apparatus 1 stores a plurality of, e.g., sixteen identification signals ID₁, ID₂, ..., ID₁₆.

0038When a key apparatus 1 receives a random number signal X of 24 bits, for example, from a lock apparatus 10, a signal processing circuit unit 3 of the key apparatus 1 determines which of random number signals X₁, X₂, ..., X₁₆ a random number signal formed of lower 4 bits of the 24 bits of the received random number signal X is, and, if the lower 4-bit random number signal is a random number signal X₁, selects one of sixteen identification signals ID₁, ID₂, ..., ID₁₆ stored in the memory unit 5, e.g., the identification signal ID₁ in response to the random number signal X₁.

0039In this embodiment, as shown in Table 2, the random number signals X₁, X₂,..., X₁₆ formed of the lower 4 bits of the above 24-bit random number signal X respectively correspond to sixteen identification signals ID₁, ID₂, ..., ID₁₆ stored in the memory unit 5. <tables id="tabl0002" num="0002"><table frame="all"><title>Table 2</title><tgroup cols="3" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="center">lower 4-bit random number</entry><entry namest="col2" nameend="col2" align="center">identification signal</entry><entry namest="col3" nameend="col3" align="center">encrypted signal</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">X₁ = 0000</entry><entry namest="col2" nameend="col2" align="center">ID₁</entry><entry namest="col3" nameend="col3" align="center">f(X, ID₁)</entry></row><row><entry namest="col1" nameend="col1" align="center">X₂ = 0001</entry><entry namest="col2" nameend="col2" align="center">ID₂</entry><entry namest="col3" nameend="col3" align="center">f(X, ID₂)</entry></row><row><entry namest="col1" nameend="col1" align="center">:</entry><entry namest="col2" nameend="col2" align="center">:</entry><entry namest="col3" nameend="col3" align="center">:</entry></row><row><entry namest="col1" nameend="col1" align="center">:</entry><entry namest="col2" nameend="col2" align="center">:</entry><entry namest="col3" nameend="col3" align="center">:</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">X₁₆ = 1111</entry><entry namest="col2" nameend="col2" align="center">ID₁₆</entry><entry namest="col3" nameend="col3" align="center">f(X, ID₁₆)</entry></row></tbody></tgroup></table></tables>

0040In this second embodiment, each of the sixteen identification signals ID₁, ID₂, ..., ID₁₆ stored in the memory unit 5 is formed of 24 bits, for example.

0041In this second embodiment, the signal processing circuit unit 3 encrypts one of the identification signals ID₁, ID₂, ..., ID₁₆ selected as shown in Table 2 in response to the received one of the lower 4-bit random number signal X₁, X₂, ..., X₁₆ of the random number signal X by using the received random number signal X, and obtains one of the encrypted signals f(X, ID₁), f(X, ID₂), ..., f(X, ID₁₆) shown in Table 2. The key apparatus 1 transmits the obtained one of the encrypted signals f(X, ID₁), f(X, ID₂), ..., f(X, ID₁₆) to the lock apparatus 10.

0042The same identification signals, e.g., the sixteen identification signals ID₁, ID₂, ..., ID₁₆ stored in the memory unit 5 of the key apparatus 1 are also stored in the memory unit 13 of the lock apparatus 10 shown in FIG. 4.

0043The signal processing circuit unit 12 of the lock apparatus 10 stores the 24-bit random number signal X, for example, generated by the random number generating unit 14 and transmitted therefrom in response to the response request signal from the key apparatus 1, and selects one of, for example, the sixteen identification signals ID₁, ID₂, ..., ID₁₆ stored in the memory unit 13 similarly to the key apparatus 1 in response to the selected one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X.

0044In this case, the identification signal selected by the key apparatus 1 in response to one of the lower 4-bit random number signal X₁, X₂, ..., X₁₆ of the random number signal X is set the same as the identification signal selected by the lock apparatus 10 in response to the same one of the lower 4-bit random number signal X₁, X₂, ..., X₁₆ of the random number signal X.

0045When the lock apparatus 10 receives from the key apparatus 1 one of the encrypted signals f(X, ID₁), f(X, ID₂), ..., f(X, ID₁₆) obtained by encrypting the selected one of the identification signals ID₁, ID₂, ..., ID₁₆, e.g., the encrypted signal f(X, ID1) by using the random number signal X, the signal processing circuit unit 12 decrypts the encrypted signals f(X, ID₁) in accordance with a predetermined function f^-1{f(X, ID₁), X} by using the identification signal ID₁ selected in response to the random number signal X₁, for example, selected from the lower 4-bit random number signals X₁, X₂,..., X₁₆ of the random number signal X, and checks whether or not the identification signal ID₁ obtained by the decryption coincides with the one of the identification signals ID₁, ID₂,..., ID₁₆ previously selected in response to the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X, e.g., the identification signal ID₁.

0046Other parts and units of the identification signal checking apparatus according to the second embodiment shown in FIG. 4 are arranged similarly to those of the identification signal checking apparatus according to the first embodiment shown in FIG. 1.

0047An operation of the keyless entry system for opening and closing a door according to the second embodiment shown in FIG. 4 will be described with reference to FIG. 5 which is a flowchart therefor. In this second embodiment, it is assumed that the same sixteen identification signals ID₁, ID₂, ..., ID₁₆ formed of codes of 24 bits, for example, are previously stored (registered) in both of the memory units 5 and 13.

0048In step S21 of the flowchart shown in FIG. 5, the switch unit 2 of the key apparatus 1 is operated, thereby a command to open or close a door being issued. In step S22, as shown in FIG. 3A, for example, the key apparatus 1 transmits the response request signal including the door opening/closing command signal to the lock apparatus 10 for a period of 100 ms. Then the processing proceeds to step S23.

0049In step S23, the lock apparatus 10 receives the response request signal as shown in FIG. 3D. Then, the processing proceeds to step S24, wherein the lock apparatus 10 obtains the 24-bit random number signal X, for example, generated by the random number generating unit 14. In step S25, as shown in FIG. 3C, the lock apparatus 10 transmits the random number signal X to the key apparatus 1 for the period of 30 ms, for example. Then, the processing proceeds to step S26.

0050In step S26, the key apparatus 1 receives the random number signal X as shown in FIG. 3B. Then, the processing proceeds to step S27, wherein the key apparatus 1 selects one of the sixteen identification signals ID₁, ID₂, ..., ID₁₆ registered in the memory unit 5, e.g., the identification signal ID₁ in response to one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X. Then, the processing proceeds to step S28.

0051In step S28, the key apparatus 1 encrypts the selected identification signal ID₁ to convert it into the 24-bit code signal, in accordance with a predetermined function f(X, ID₁) by using the 24-bit random number signal X, for example, and then obtains the encrypted signal f(X, ID₁). Then, the processing proceeds to step S29, wherein the key apparatus 1 transmits the encrypted signal f(X, ID₁) to the lock apparatus 10 during the period of 30 ms, for example, as shown in FIG. 3A. Then, the processing proceeds to step S30.

0052In step S30, the lock apparatus 10 receives the encrypted signal f(X, ID₁) as shown in FIG. 3D. Then, the processing proceeds to step S31, wherein the lock apparatus 10 decrypts the received encrypted signal f(X, ID₁) in accordance with a predetermined function f^-1{f(X, ID₁), X} by using the previously transmitted random number signal X. Then, the processing proceeds to step S32.

0053In step S32, the lock apparatus 10 checks whether or not the decrypted identification signal ID₁ coincides with the one of the sixteen identification signals ID₁, ID₂, ..., ID₁₆ registered in the memory unit 13, e.g., the identification signal ID₁ selected in response to the selected one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X. In step S33, as a result of the check processing, if the decrypted identification signal ID₁ coincides with the selected identification signal ID₁, then, in accordance with the door opening or closing command signal of the response request signal, the signal processing circuit unit 12 supplies the unlocking or locking command signal to the drive unit 15 for carrying out the unlocking or locking operation of the door. Under the control of the drive unit 15, the door is opened or closed.

0054Since the identification signal checking apparatus according to the second embodiment shown in FIG. 4 is arranged as described above, it can easily be understood that it is possible to achieve the same effect as that of the identification signal checking apparatus according to the embodiment shown in FIG. 1. According to the second embodiment shown in FIG. 4, since one of the sixteen identification signals ID₁, ID₂, ..., ID₁₆ is selected in response to one of the lower 4-bit random number signals X1, X₂, ..., X₁₆ of the random number signal X, it is advantageously possible to improve the security further.

0055The identification signal checking apparatus according to a third embodiment of the present invention will be described with reference to FIGS. 6 and 7. In FIG. 6, parts and units corresponding to those in FIG. 1 are marked with the same reference numerals and hence need not to be described in detail.

0056In the third embodiment shown in FIG. 6, a nonvolatile memory unit 5 of a portable key apparatus 1 stores a specific (own) identification signal ID and a plurality of, e.g., sixteen functions f₁, f₂,..., f₁₆.

0057When the key apparatus 1 receives a random number signal X of 24 bits, for example, from a lock apparatus 10, a signal processing circuit unit 3 of the key apparatus 1 determines which of random number signals X₁, X₂,..., X₁₆ a random number signal formed of lower 4 bits of the 24 bits of the received random number signal X is, and, if the lower 4-bit random number signal is a random number signal X₁, for example, selects one of sixteen functions f₁, f₂,..., F₁₆ stored in a memory unit 5, e.g., the function f₁ in response to the random number signal X₁.

0058In this third embodiment, as shown in Table 3, the random number signals X₁, X₂,..., X₁₆ formed of the lower 4 bits of the above 24-bit random number signal X respectively correspond to the sixteen functions f₁, f₂,..., F₁₆ stored in the memory unit 5. <tables id="tabl0003" num="0003"><img file="EP0807733A2_D0001.tif" /></tables><tables id="tabl0004" num="0004"><img file="EP0807733A2_D0002.tif" /></tables>

0059In this third embodiment, the identification signal ID stored in the memory unit 5 is formed of 24 bits, for example.

0060In this embodiment, the signal processing circuit unit 3 encrypts the identification signal ID by using the received random number signal X and one of the functions f₁, f₂, ..., f₁₆ selected in response to one of the lower 4-bit random number signal X₁, X₂, ..., X₁₆ of the random number signal X, and obtains one of the encrypted signals f₁(X, ID), f₂(X, ID),..., f₁₆(X, ID) shown in Table 3. The key apparatus 1 transmits the obtained one of the encrypted signals f₁(X, ID), f₂(X, ID), ..., f16(X, ID) to the lock apparatus 10.

0061The same identification signal and the same plurality of, e.g., sixteen functions f₁, f₂,..., f₁₆ stored in the memory unit 5 of the key apparatus 1 are also stored in the memory unit 13 of the lock apparatus 10 shown in FIG. 6.

0062The signal processing circuit unit 12 of the lock apparatus 10 stores the 24-bit random number signal X, for example, generated by the random number generating unit 14 and transmitted therefrom in response to the response request signal from the key apparatus 1, and selects one of, for example, the sixteen functions f₁, f₂, ..., f₁₆ stored in the memory unit 13 similarly to the key apparatus 1 in response to the received one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X.

0063In this case, one of the functions f₁, f₂,..., f₁₆ selected by the key apparatus 1 in response to one of the lower 4-bit random number signal X₁, X₂, ..., X₁₆ of the random number signal X is set the same as one of the functions f₁, f₂,..., f₁₆ selected by the lock apparatus 10 in response to one of the lower 4-bit random number signals X₁, X₂,..., X₁₆ of the random number signal X.

0064When the lock apparatus 10 receives from the key apparatus 1 one of the encrypted signals f₁(X, ID), f₂(X, ID, ..., f₁₆(X, ID) obtained by encrypting the identification signal ID by using the selected one of the functions f₁, f₂,..., f₁₆ and the random number signal X, e.g., the encrypted signal f₁(X, ID), the signal processing circuit unit 12 decrypts the encrypted signals f1(X, ID) in accordance with a predetermined function f₁^-1{f₁(X, ID), X} by using the previously transmitted 24-bit random number signal X and the function f₁ selected in response to one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X, e.g., selected in response to the random number signal X₁, and checks whether or not the identification signal ID obtained by the decryption coincides with the identification signal ID previously registered in the memory unit 13.

0065Other parts of the identification signal checking apparatus according to the third embodiment shown in FIG. 6 are arranged similarly to those of the identification signal checking apparatus according to the first embodiment shown in FIG. 1.

0066An operation of the keyless entry system for opening and closing a door according to the third embodiment shown in FIG. 6 will be described with reference to FIG. 7 which is a flowchart therefor. In this third embodiment, it is assumed that the identification signal and the sixteen functions f₁, f₂, ..., f₁₆ are previously registered (stored) in both of the memory units 5 and 13.

0067In step S41 of the flowchart shown in FIG. 7, the switch unit 2 of the key apparatus 1 is operated, thereby a command to open or close a door being issued. In step S42, as shown in FIG. 3A, for example, the key apparatus 1 transmits the response request signal including the door opening/closing command signal to the lock apparatus 10 for a period of 100 ms. Then, the processing proceeds to step S43.

0068In step S43, the lock apparatus 10 receives the response request signal as shown in FIG. 3D. Then, the processing proceeds to step S44, wherein the lock apparatus 10 obtains the 24-bit random number signal X, for example, generated by the random number generating unit 14. In step S45, as shown in FIG. 3C, the lock apparatus 10 transmits the random number signal X to the key apparatus 1 for a period of 30 ms, for example. Then, the processing proceeds to step S46.

0069In step S46, the key apparatus 1 receives the random number signal X as shown in FIG. 3B. Then, the processing proceeds to step S47, wherein the key apparatus 1 selects one of the sixteen functions f₁, f₂,..., f₁₆ registered in the memory unit 5, e.g., the function f₁ in response to one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X. Then, the processing proceeds to step S48.

0070In step S48, the key apparatus 1 encrypts the identification signal ID to convert it into the 24-bit code signal, by using the selected function f1 and the 24-bit random number signal X, for example, and then obtains the encrypted signal f₁(X, ID). Then, the processing proceeds to step S49, wherein the key apparatus 1 transmits the encrypted signal f₁(X, ID) to the lock apparatus 10 during the period of 30 ms, for example, as shown in FIG. 3A. Then, the processing proceeds to step S50.

0071In step S50, the lock apparatus 10 receives the encrypted signal f₁(X, ID) as shown in FIG. 3D. Then, the processing proceeds to step S51, wherein the lock apparatus 10 decrypts the received encrypted signal f₁(X, ID) in accordance with a predetermined function f₁^-1{f₁(X, ID), X} by using the previously transmitted random number signal X and the corresponding one of the random number signals X₁, X₂, ..., X₁₆ of the random number signal X. Then, the processing proceeds to step S52.

0072In step S52, the lock apparatus 10 checks whether or not the decrypted identification signal ID coincides with the identification signal ID registered in the memory unit 13. In step S53, as a result of the check processing, if the decrypted identification signal ID coincides with the identification signal ID registered in the memory unit 13, then, in accordance with the door opening or closing command signal of the response request signal, the signal processing circuit unit 12 supplies the unlocking or locking command signal to the drive unit 15 for carrying out the unlocking or locking operation of the door. Under the control of the drive unit 15, the door is opened or closed .

0073Since the identification signal checking apparatus according to the third embodiment shown in FIG. 6 is arranged as described above, it can easily be understood that it is possible to achieve the same effect as that of the identification signal checking apparatus according to the first embodiment shown in FIG. 1. According to the third embodiment shown in FIG. 6, since one of the sixteen functions f₁, f₂,..., f₁₆ is selected in response to one of the lower 4-bit random number signals X₁, X₂, ...,X₁₆ of the random number signal X, it is advantageously possible to improve the security further.

0074While in the first to third embodiments the communication between the key apparatus 1 and the lock apparatus 10 is carried out in accordance with the base band system by using the infrared rays, the communication may be carried out in accordance with some other modulation systems such as the ASK, the FSK or the like by using the infrared rays. It is needless to say that the communication may be carried out by using a radio wave or a supersonic wave instead of the infrared rays.

0075It is not necessary that each of the random number signal, the identification signal and the encrypted signal is formed of 24 bits. It is sufficient to determine the number of bits thereof in response to a required degree of the security.

0076While in the first to third embodiments the response request signal includes the locking or unlocking command signal, the locking or unlocking command signal may be added to the above encrypted signal or may be transmitted individually.

0077In the above embodiments, the number of the identification signals ID₁, ID₂, ..., ID₁₆ or the functions f₁, f₂,..., f₁₆ is set to 16, it is not necessary to set the number to 16, and hence the number may be set to any value depending upon a desired degree of security.

0078While in the above embodiments one of the identification signals ID₁, ID₂, ..., ID₁₆ or one of the functions f₁, f₂, ..., f₁₆ is selected in response to one of the lower 4-bit random number signals X₁, X₂, ..., X₁₆ of the random number signal X, it is not necessary to use the lower 4 bits of the random number signal X and one of the identification signals ID₁, ID₂, ..., ID₁₆ or one of the functions f₁, f₂,...,f₁₆ may be selected by using any bits of the random number signal X.

0079According to the first to third embodiments of the present invention, the detecting apparatus (lock apparatus) transmits the random number signal, and the apparatus to be detected (key apparatus) encrypts the identification signal by using the random number signal and transmits the encrypted identification signal to the detecting apparatus (lock apparatus). Therefore, since the identification signal transmitted from the apparatus to be detected (key apparatus) to the detecting apparatus (lock apparatus) is the encrypted signal obtained by encryption using the random number signal and hence is always a unique signal, the security is advantageously improved.

0080According to the embodiments of the present invention, since it is not necessary to manage the apparatus to be detected (key apparatus) and the detecting apparatus (lock apparatus) as a pair of items or objects to be managed, this leads to advantages in effective management and physical distribution.

0081Having described preferred embodiments of the present invention with reference to the accompanying drawings, it is to be understood that the present invention is not limited to the above-mentioned embodiments and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the present invention as defined in the appended claims.