JP2002261749A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speed up processes, while ensuring a high security, in a communication system for remote-controlling home apparatus over a global network 105. SOLUTION: The system holds unique identification codes, corresponding to a plurality of combinations of encryption algorithms with keys in a home terminal 100 and an IC card 107, in advance. For remote-controlling a home apparatus, it sets the IC card 107 in a public terminal, encrypts control data, using an encryption algorithm and a key corresponding to the identification code and transmits the encryption and the identification code to the home terminal 100, which is then decodes the encryption to generate the control data, using the encryption algorithm and the key corresponding to the received identification code.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a communication system, and more particularly to a communication system for remotely controlling home appliances using an IC card.

[0002]

2. Description of the Related Art In recent years, home appliances have been connected to a communication system using a wide area network, and personal terminals have been connected to arbitrary terminals.
It has been proposed that a home device can be remotely controlled and operated after authenticating a user using a C card (Integrated Circuit Card). As a technique for performing authentication in such a system, for example, an electronic signature using a public key cryptosystem is known.

FIG. 1 shows a communication system for remotely controlling household equipment such as a video tape recorder (hereinafter, referred to as VTR) and an air conditioner (air conditioner) using an IC card. In this figure, reference numeral 100 denotes a home terminal, and the home terminal 100 includes a VTR 1
01, an air conditioner 102, a rice cooker 103 and other home appliances are connected, and a local area network (LAN) 1
04 is configured.

On the other hand, the home terminal 100 is connected to a public terminal (external terminal) 106 via a wide area network 105. In the figure, the public terminal 106 has the IC card 10
7 shows a state in which the user intends to set 7, but the IC card 107 can also be set in the home terminal 100.

[0005] Next, in this system configuration, authentication of a user by a public key method will be described.

First, in the home terminal 100, a public key Pu and a secret key Pa are generated in advance, and a unique synchronization (SYNC) pattern is encrypted using the public key Pu (SYNC, P
u) to generate the cipher A. Then, this encryption A is
It is stored in the C card 107.

At the time of authentication, the cipher A of the IC card 107 is transmitted from the public terminal 106 to the home terminal 100 via the wide area network 105. The home terminal 100 decrypts the encryption A using the secret key Pa (encryption A, Pa) and generates the decryption B. If the decryption B matches the SYNC pattern, authentication is established and communication is continued,
If they do not match, the communication is terminated assuming that the authentication has failed.

[0008]

However, in the above-mentioned conventional configuration, encryption and decryption of the public key cryptosystem are generally more secure than the common key cryptosystem, but the amount of calculation is large, so that the encryption and decryption of the public key cryptosystem are required for authentication. It takes longer time. Also, for example, RSA (Rive) which is a public key cryptosystem using prime numbers
In the st, Shamir, Adleman) cryptosystem, at present, no method has been found for generating and verifying a prime number once, so that it takes time to generate a key. Therefore, in order to increase the speed by this method, a processor with high performance is required, and there is a problem that the system becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a communication system using an IC card which has high security without using a public key cryptosystem. And to increase the processing speed without using a high-performance processor.

[0010]

According to the present invention, an identification code for specifying one of a plurality of pairs of a key and an encryption algorithm is transmitted and received between the IC card and the home terminal together with the encryption.

Specifically, a first solution taken by the present invention is to connect an IC card to an external terminal on a network in which the home terminal and the external terminal are connected, and connect the home terminal to the home terminal. It is premised on a communication system that remotely controls devices.

[0012] In this communication system, the home terminal and the IC card each have the same contents in which a plurality of keys and encryption algorithms are associated with each other in one-to-one correspondence and individual identification codes are assigned to each pair. There is provided storage means for storing. Further, the IC card, when set in the external terminal, generates encryption using one of the plurality of pairs of the key and the encryption algorithm, and transmits control data for transmitting data together with an identification code corresponding to the pair. The home terminal includes control means for determining a corresponding key and an encryption algorithm from the identification code of the data received from the external terminal and decrypting the encryption.

[0013] With this configuration, the control means of the IC card encrypts the control data of the home appliance with one of the pair of the key and the encryption algorithm stored in the storage means, and transmits the control data from the external terminal to the home. And transmits the code together with the identification code corresponding to the pair to the terminal. Further, the home terminal specifies a key and an encryption algorithm from the received identification code and the content of the storage means, and decrypts the encryption. Therefore, the control of the home appliance can be executed based on the decrypted control data and the like.

[0014] A second solution taken by the present invention is:
In the first solution, the home terminal includes random number generation means for generating a random number to generate a plurality of keys and an identification code, and the home terminal and the IC card have a plurality of cryptographic algorithms having a plurality of cryptographic algorithms. Holding means is provided. And the storage means of the home terminal and the IC card are:
With the IC card set in the home terminal, one key is associated with one encryption algorithm and one identification code and stored in a combination of two or more.

In the first solution, the contents of the key and the encryption algorithm assigned with the identification code may be stored in the storage in advance. In the second solution, a plurality of keys and the identification code are generated by random numbers. In addition, the contents of assigning identification code while pairing the key and encryption algorithm,
It is stored in the storage means of the home terminal and the IC card. In this case, it becomes easy to appropriately update the key and the encryption algorithm.

According to a third solution taken by the present invention, in the first or second solution, a plurality of home appliances are connected to the home terminal, and the home terminal and the IC card are connected to a key. And a combination in which an identification code corresponding to a pair of an encryption algorithm and an encryption algorithm is assigned to each household device. Further, the control means of the IC card generates a cipher using the key and the encryption algorithm corresponding to the identification code of the home appliance to be controlled in a state where the IC card is set in the external terminal, and generates the cipher together with the identification code. The control means of the home terminal determines the corresponding key and encryption algorithm from the identification code of the data received from the external terminal, decrypts the encryption, and decodes the encryption. It is configured to specify a device for use.

With this configuration, the encryption generated using a different key and encryption algorithm for each home device to be controlled is transmitted between the IC card and the home terminal together with the corresponding identification code. You.

Further, a fourth solution taken by the present invention is:
In the second solving means, the home terminal and the storage means of the IC card may be configured to add or subtract the access number data with the value generated by the random number generating means as an initial value and the access number data. And a change value generated by the random number. Further, the control means of the IC card generates an encryption including access number data using one of the plurality of pairs of the key and the encryption algorithm in a state where the IC card is set in the external terminal, and corresponds to the pair. The control means of the home terminal decodes the data received from the external terminal, compares the access count data of the IC card with the access count data of the home terminal, When the two access count data match, the control of the home appliance is executed, and when the two access count data are different, the IC card side is urged to change the access count data. Further, after changing the access count data, the control means of the IC card is configured to perform communication using an encryption algorithm and a key corresponding to an identification code different from that before the change.

With this configuration, the encryption including the access count data is communicated with the identification code between the IC card and the home terminal, and the access count data on the IC card side and the access count data on the home terminal side are transmitted. By comparing with the above, it is determined whether or not the control of the home appliance can be performed. If the access count data does not match, the access count data on the IC card side is updated, and then encryption is generated again using a key and an encryption algorithm corresponding to a different identification code, and communication is performed.

[0020]

According to the first and second means, only the identification code is disclosed, so that high security can be ensured. In addition, since a common key cryptosystem having a smaller processing amount than the public key system is used, the processing speed can be increased without using an expensive processor with high performance.

Further, according to the third solution, since an individual identification code is used for each household device, it is assumed that an encryption algorithm and a key corresponding to one household device are found. However, the influence on other household appliances can be reduced.

According to the fourth solution, when the access count data is changed, an identification code different from that before the change is used, so that a third party analyzes the access count data. It is difficult as well.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) This embodiment 1 relates to a communication system for remotely controlling home appliances such as a VTR 101 using an IC card 107 as shown in FIG. The IC card 107 is configured as follows.

First, the internal configurations of the home terminal 100 and the IC card 107 will be described with reference to FIG. As shown in the figure, inside the home terminal 100, a random number device 200 as a random number generating means for generating a random number, a nonvolatile random access memory (RAM) 201 as a storage means for holding control data, and a wide area network 105 And LAN
A network interface (network I / F) 202 for performing communication via the communication terminal 104; a read-only memory (RO) for holding program data necessary for controlling the home terminal 100 and a plurality of encryption algorithms;
M) 203, a central processing unit (CPU) 204 as control means for performing control according to data in the ROM 203,
A card interface (card I / F) 205 for communicating with the IC card 107 is provided, and these components 200 to 205 are connected to each other.

The random number device 200 is used to generate a random number, thereby generating a key required for generating and decrypting a cipher, and a unique identification code corresponding to the key. In this embodiment, the random number is generated by using the random number device 200. However, instead of providing the random number device 200, the random number may be generated by a program in the ROM 203.

The home terminal 100 has an operation panel (not shown). The operation panel is provided for previously writing necessary data to an IC card 107 used when remotely controlling the VTR 101 or the like using the public terminal (external terminal) 106.

The IC card 107 has,
Card I / F 206 for communicating with home terminal 100 and public terminal 106, non-volatile R as storage means
An AM 207, a ROM 208 for holding a program necessary for controlling the IC card 107, and a CPU 209 as control means for performing control in accordance with data in the ROM 208 are provided, and these components 206 to 209 are connected to each other. The same encryption algorithm as that of the home terminal 100 is stored in the ROM 208 (or the RAM 207).

The operation of this system is performed as follows.

First, the operation panel is operated on the home terminal 100 side, and the ROM 2 as the encryption algorithm holding means is operated.
One is selected from a plurality of cryptographic algorithms stored in 03, and a key and a unique identification code required for cryptography are generated by the random number device 200. Then, as shown in Table 1, the generated identification code and key are stored in the RAM 201 while associating the generated identification code and key with the address of the program of the selected encryption algorithm.

[0031]

[Table 1]

Here, the identification code is a unique code corresponding to the key as described above, and when generating a plurality of keys, the CPU 204 controls so that the identification code in Table 1 does not have the same identification code. It shall be.

Next, the IC card 107 is inserted into the home terminal 10.
0, and the card I / F 206 of the IC card 107 is connected to the card I / F 205 of the home terminal 100. Then, the information of Table 1 stored in the RAM 201 is stored in the RAM 207 from the card I / F 205 of the home terminal 100 via the card I / F 206 of the IC card 107 under the control of the CPU 209. That is, the information in Table 1 is stored in both the home terminal 100 and the IC card 107.
The IC card 107 may be set in the home terminal 100 after the creation of the data in Table 1, or may be set in the home terminal 100 before the creation of the data in Table 1.

Next, the public terminal 106 and the home terminal 10 for remotely controlling the home device using the IC card 107 are described.
The communication state at 0 will be described with reference to FIG. In the figure, 300 of the public terminal 106 is IP address data representing the address of the home terminal 100 (here, an IP address), 301 is a unique identification code corresponding to the key, and 302 is encrypted data. The encrypted data 302 includes a SYNC pattern 303 used as information indicating whether data before encrypting the encrypted data 302 is genuine data, and control data 304 for home appliances. Further, the control data 304 includes air conditioner control data 305 and VTR control data 306.
And so on.

On the other hand, reference numeral 307 of the home terminal 100 denotes IP address data indicating the address of the public terminal 106;
Is an identification code, and 309 is encrypted data. Also, 31
0 is information before encrypting the encrypted data 309,
The content is ACK information (reception information) indicating completion of data reception from the public terminal 106.

In this system, when a household device is remotely operated, first, a personal IC card 107 is inserted into the public terminal 106 and set. And this public terminal 1
In order to operate the home terminal 100 at home at 06, the control data which is data including the IP address data 300 of the home terminal 100, the identification code 301, and the type and content of the home device at the public terminal 106. Set 304.

The contents set by the public terminal 106 are IC
It is stored in the RAM 207 of the card 107. The CPU 209 of the IC card 107 transmits the encryption algorithm and the key corresponding to the set identification code to the RA based on Table 1.
It is specified from M207. Then, using the algorithm and key corresponding to the identification code, the control data 3
04, a SYNC pattern 303 stored in the ROM 208 as information indicating the authenticity of the control data 304.
Are encrypted to generate encrypted data 302. Further, the IP address data 300, the identification code 301, and the encrypted data 302 shown on the public terminal side in FIG.
Create transmission data of a predetermined format consisting of
This is transmitted to the home terminal 100 via the wide area network 105 together with the IP address data 307 of the public terminal 106.

On the home terminal side receiving the data, the CPU 204
Determines the encryption algorithm and the key corresponding to the transmitted identification code 301 by referring to the contents of Table 1 held in the RAM 201. The encryption algorithm and the key are the same as those used for generating the encryption on the public terminal 106 side. Then, the encrypted data 302 is decrypted using the key and the encryption algorithm, and the SYNC pattern 30 is decrypted.
3 and control data 304 are generated.

Here, the ROM 203 of the home terminal 100
Holds a SYNC pattern corresponding to each device type and control content included in the control data 304. Then, in the home terminal 100, the decrypted SYNC pattern 303 and the SY pattern held by the home terminal 100 are stored.
Compare with the NC pattern. As a result of the comparison, if they match, it is determined that the control data 304 is genuine data, and the CPU 204 controls the household device using the control data 304 via the LAN 104.

When the SYNC patterns match, the home terminal 100 controls the CPU 204 to
The identification code 30 based on the random number generated by the random number device 200
8 is generated, and ACK information 310 indicating reception completion is encrypted from the information in Table 1 held in the RAM 201 using an encryption algorithm and a key corresponding to the identification code 308 to generate encrypted data 309. Then, it generates reception signal data of a predetermined format including the received IP address data 307 and the generated identification code 308 and encryption data 309, and transmits this signal to the public terminal 106 via the wide area network 105.

At the public terminal 106 receiving this signal,
The CPU 209 determines the encryption algorithm and the key corresponding to the identification code 308 from the contents of Table 1 held in the RAM 207, decrypts the encrypted data 309, and confirms the ACK information 310, thereby terminating the communication.

By doing so, it is possible to perform encrypted communication using the common key system without distributing information about encryption such as a key and an encryption algorithm. Updating enables highly secure communication between two points. Also, while securing the same security as the public key cryptosystem, the amount of operation is smaller than that of the public key cryptosystem, so that the processing speed can be increased without using a high-performance processor. It is also possible to prevent an increase in cost.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, in the communication system of the first embodiment, an individual identification code is assigned to each household device to be controlled.
Here, a description will be given assuming that the VTR 101 and the air conditioner 102 are controlled.

FIG. 4 shows a communication state between the public terminal 106 and the home terminal 100 when the home devices 101 and 102 are remotely controlled using the IC card 107 in this embodiment. In the figure, 400 of the public terminal 106 is IP address data representing the address of the home terminal 100, 4
01 is an identification code A, 40 which is an identification code for a VTR.
Reference numeral 2 denotes encrypted VTR control data, reference numeral 403 denotes an air conditioner identification code B, and reference numeral 404 denotes encrypted air conditioner control data.

405 of the home terminal 100 is IP address data indicating the address of the public terminal 106;
Is ACK information indicating completion of reception of information on the air conditioner,
Reference numeral 407 denotes ACK information indicating completion of reception of information on the VTR. Note that 401 is an air conditioner identification code A, and 403 is a VTR identification code B, as described on the public terminal 106 side.

In the system of the present embodiment, it is assumed that, at the time of creating the data of Table 1 described in the first embodiment, a home device is assigned to each identification code. That is, while making each identification code correspond to a key and an encryption algorithm, a home device corresponding to each identification code is also set at the same time. Then, the data of Table 2 created in this way is stored in the RAM 201 of the home terminal 100 and the RAM 2 of the IC card 107.
07.

[0047]

[Table 2]

In this system, the home appliance 10
When remote-controlling the terminals 1 and 102 from the public terminal 106, first, the personal IC card 107 is set in the public terminal 106, and the public terminal 106
00 is set as the IP address data 400, and the identification code and control data of the home appliance to be controlled are also set.

Here, the home equipment to be remotely controlled is VT
R101 and air conditioner 102. As described above, the identification code and the control data are the identification code A 401 and the control data 402 for the VTR 101, and the identification code B 403 and the control data 404 for the air conditioner 102.
And

The contents set by the public terminal 106 are IC
It is stored in the RAM 207 of the card 107. And I
The CPU 209 of the C card 107 reads the table 2 stored in advance.
The encryption algorithm and key corresponding to each identification code of
It is determined from M207, and the control data 402 and control data 404 of the home appliance are encrypted using an algorithm and a key corresponding to the identification code. Then, as shown on the public terminal 106 side of FIG. 4, the IP address data 400, the identification code A401, the control data 402, the identification code B4
03, transmission data of a predetermined format including the control data 404 is created, and this data is
It is transmitted to the home terminal 100 via the wide area network 105 together with the P address data 405.

The received home terminal 100 has a CPU
204 determines the encryption algorithm and key corresponding to the identification code A 401 and the identification code B 403 by checking the contents of Table 2 held in the RAM 201, and at the same time determines the household device corresponding to each identification code. Then, the control data 402 and the control data 404 are respectively decrypted to generate the original control data. CPU of home terminal 100
204 transmits the control data 402 to the V
The control data 404 is transferred to the TR 101 to the air conditioner 102, and control according to the content is performed. As in the first embodiment, it is preferable to include a SYNC pattern in the encrypted data and check whether the data is authentic.

Next, the home terminal 100 is connected to the VTR 101
The information indicating the completion of the reception of the information on the
ACK information 406 is generated by encrypting using an encryption algorithm and a key corresponding to 1 and the information indicating the end of the reception of the information on the air conditioner 102 is similarly identified by the identification code B403.
A using the encryption algorithm and key corresponding to
CK information 407 is generated. Then, reception signal data of a predetermined format including the received IP address data 405, the identification code A401, the ACK information 406, the identification code B403, and the ACK information 407 is created.
This data is transmitted to the public terminal 106 via the wide area network 105.

In the received public terminal 106, the CPU 209 determines an encryption algorithm and a key from the RAM 207 according to the identification code A401 and the identification code B403 included in the received reception signal data. And ACK
The information 406 and the ACK information 407 are decoded, and this AC
After confirming the K information, the communication ends.

As described above, if the identification code is set to be different for each device, even if the encryption algorithm and key of one home device are found out, the influence on other home devices can be suppressed, and the RAM 201 is periodically registered. By updating the data in Table 2 of the RAM 207, more secure communication becomes possible. Also, in this case, the amount of calculation is smaller than that of the conventional public key method, so that the processing speed can be increased without using a high-performance processor as in the first embodiment, and the system cost is reduced. It can be prevented from becoming high.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. Embodiment 3
Is the home appliance 1 in the communication system of the first embodiment.
The access number data is used for authentication between 00 and the public terminal 106.

FIG. 5 shows a communication state performed using the access count data of the home terminal 100 and the access count data of the IC card 107. 500 is the number of access times data held by the IC card 107, and 501 is I
The change value held by the C card 107, 502 is the number of access times data held by the home terminal 100, 503
Is a changed value held by the home terminal 100. In FIG. 5, the same reference numerals as those in FIG. 3 indicate information having the same function.

In this system, first, in the configuration shown in FIGS. 1 and 2, the CPU 204 of the home terminal 100 causes the random number device 200 to generate two random numbers. Then, one random number is stored in the RAM 201 as the access number data 502, and the other random number is stored in the RAM 201 as the changed value 503. Similarly, the two random numbers are stored in the RAM 207 via the card I / F 205 and the card I / F 206. The random number corresponding to the access count data 502 is set as the access count data 500, and the random number corresponding to the change value 503 is set as the change value 501. In addition, the data of Table 1 is created together with these data.

Communication between the home terminal 100 and the public terminal 106 using the access count data 500 and 502 is performed as follows. First, when the identification code 301 and the control data 304 are set in the public terminal 106 as in the example of FIG. 3, as shown in FIG. 5, the SYNC pattern 303 and the control data 304 include the access count stored in the IC card 107. From the data to which the data 500 has been added, the encrypted data 30 is obtained using the key corresponding to the identification code and the encryption algorithm.
2 is generated. Then, the encrypted data 302
The data is transferred to the home terminal 100 together with the P address data 300 and the identification code 301. The home terminal 100
The key and the encryption algorithm are specified from the identification code 301, and the encrypted data 302 is decrypted. Further, the received access count data 500 of the IC card 107 is
The authenticity of the communication is determined by comparing with the access number data 502 stored in the RAM 201 under the control of 204.

FIG. 6 shows the access count data 500 in FIG.
FIG. 7 is a conceptual diagram showing the update of the access count data 500 and 502 when the access count data 502 matches the access count data 502. FIG. 7 shows the access count when the access count data 500 and the access count data 502 in FIG. FIG. 9 is a conceptual diagram illustrating updating of data 500 and 502.

In FIG. 5, access number data 500,
If the numbers 502 match, the CPU 204 of the home terminal 100 controls the home appliance and adds the change value 503 to the access count data 502 assuming that the communication has been established. Then, this value is held as the access count data 502 of the next communication, and the
Send K information. In FIG. 6, the access count data 50
If 2 is "5", add the change value "3" and "8"
And transmitting the ACK information.

When the ACK information is received, public terminal 106 adds change value 501 to access number data 500 and holds the value as access number data 500 for the next communication. In FIG. 6, the public terminal 106 also updates the access count data 500 from “5” to “8”.

On the other hand, FIG.
If the numbers 502 do not match, it is determined that communication has not been established, and a mismatch code urging the updating of the access count data 500, 502 is sent to the public terminal 1 as shown in FIG.
06.

The public terminal 10 receiving the mismatch code
6 adds the change value 501 to the stored access count data 500 and sets the value to the access count data 500.
To the home terminal 100 again. In the figure,
“5” is updated to “8” and transmitted again.

In this case, if the identification code at the start of communication is the identification code A, the CPU 209 of the IC card 107 on the side of the public terminal 106 has received a change request from the home terminal 100 due to mismatch of the access count data. When the public terminal 106 changes the access count data 500 and retransmits the data, the identification code 301 is changed from the previous time to use the identification code B.

In the home terminal 100 as well, the IP address data of the public terminal requesting the change of the access count data and the identification code at that time are stored in the RAM 201, and if the transmission is performed from the IP address, the identification code 3 is used.
Check if 01 has been changed. If they match, transmission and reception of ACK information and access count data 50
The communication is terminated by updating 0, 502, and if they do not match, the held IP address data 300 and the identification code 301 are deleted, and the communication is continued.

In FIGS. 6 and 7, the ACK information and the mismatch code may be encrypted and transmitted together with the identification code.

As described above, the access count data 500, 5
02 so that the access number data 50
By making the identification code different each time communication is performed so as to match when 0 and 502 are different, the identification code 301 is different for each communication even if a malicious person attempts to uncover the access count data 500 and 502. Because of this, analysis is difficult, and highly secure communication between two points becomes possible.
Also, in this case, the amount of calculation is smaller than that of the common key cryptosystem, so that the processing can be speeded up without using a high-performance processor.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a network to which a communication system according to the present invention is applied.

FIG. 2 is a configuration diagram of a home terminal and an IC card.

FIG. 3 is a conceptual diagram of a protocol using an identification code.

FIG. 4 is a conceptual diagram of a protocol when an identification code is changed for each device.

FIG. 5 is a conceptual diagram of a protocol using access number data.

FIG. 6 is a conceptual diagram of communication when the access count data matches in FIG.

FIG. 7 is a conceptual diagram of communication in a case where access number data does not match in FIG. 5;

[Description of Signs] 100 Home terminal 101 VTR (home equipment) 102 Air conditioner (home equipment) 103 Rice cooker (home equipment) 104 LAN 105 Wide area network 106 Public terminal (external terminal) 107 IC card 200 Random number generator ( Random number generation means) 201 RAM (storage means) 202 network I / F 203 ROM (encryption algorithm holding means) 204 CPU (control means) 205 card I / F 206 card I / F 207 RAM (storage means) 208 ROM (encryption algorithm) Holding means) 209 CPU (control means) 300 IP address data 301 Identification code 302 Encrypted data 303 SYNC pattern 304 Control data 305 Air-conditioner control data 306 VTR control data 307 IP address data 308 Identification code 309 Encrypted data 310 ACK information 400 IP address data 401 Identification code A 402 Control data 403 Identification code B 404 Control data 405 IP address data 406 ACK information 407 ACK information 500 Access count data 501 Change value 502 Access count data 503 Change value

Claims (4)

[Claims] 1. A communication system for connecting a home terminal and an external terminal to each other and remotely controlling home equipment on the home terminal side by connecting an IC card to the external terminal, comprising: a home terminal; And an IC card each have storage means for storing the same contents in which a plurality of keys and encryption algorithms are associated in a one-to-one pair and an individual identification code is assigned to each pair. Control means for generating a cipher from one of the plurality of pairs of the key and the cipher algorithm using one, and transmitting data together with an identification code corresponding to the pair. A communication system comprising: control means for determining a corresponding key and an encryption algorithm from an identification code of data received from a terminal and decrypting the encryption. 2. The home terminal includes random number generation means for generating a random number to generate a plurality of keys and an identification code. The home terminal and the IC card each have a cryptographic algorithm holding a plurality of cryptographic algorithms. Means for storing the home terminal and the IC card, wherein the IC card is set in the home terminal, and two or more keys are associated with one encryption algorithm and one identification code while being associated with one key. The communication system according to claim 1, wherein the communication system is configured to store the information. 3. A home terminal is connected with a plurality of home devices, and the home terminal and the IC card are combined with each other by assigning an identification code corresponding to a pair of a key and an encryption algorithm to each home device. The control means of the IC card generates an encryption using a key and an encryption algorithm corresponding to the identification code of the home appliance to be controlled while the IC card is set in the external terminal. The control means of the home terminal determines the corresponding key and encryption algorithm from the identification code of the data received from the external terminal, decrypts the encryption, and decrypts the encryption. The communication system according to claim 1, wherein the communication system is configured to specify a household device to be used. 4. The storage means of the home terminal and the IC card,
An access number data having a value generated by the random number generation means as an initial value, and a change value generated by the random number for adding or subtracting to or from the access number data are stored. Generating an encryption including access number data using one of the plurality of pairs of the key and the encryption algorithm in a state where the IC card is set in the external terminal, and transmitting the data together with the identification code corresponding to the pair; The control means of the home terminal decodes the data received from the external terminal, compares the access count data of the IC card with the access count data of the home terminal, and determines whether the two access count data match. If the access number data is different, the IC card side controls the home device. Further, after changing the access count data, the control means of the IC card performs communication using an encryption algorithm and a key corresponding to an identification code different from that before the change. 3. The communication system according to claim 2, wherein the communication system is configured as follows.