JP2670019B2 - Communication device and communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device and a communication method for encrypting and transmitting communication data in a wireless or wired network.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of a wireless or wired communication system. In FIG. 5, a plurality of terminal devices 1
00a, 100b, 100c are connected by a network line 101. Data is transmitted and received between the plurality of terminal devices 100a, 100b, 100c via the network line 101. In the case of a wireless communication system, the network line 101 does not exist.

In order to perform communication in such a communication system while keeping the communication contents secret, the transmitting side encrypts the data according to a predetermined encryption algorithm and transmits the encrypted data. On the other hand, on the receiving side, the received encrypted data is decrypted according to the decryption algorithm corresponding to the above encryption algorithm.

FIG. 6 is a diagram showing an example of a conventional communication method for encrypting and communicating data. In FIG. 6, on the transmitting side, the communication data 22a, 22b, 22c are encrypted using a fixed encryption key 21 according to a predetermined encryption algorithm. Thereby, the encrypted data 23a, 2
3b and 23c are obtained and transmitted to the receiving side.

On the receiving side, the received encrypted data 23
a, 23b, and 23c are decrypted according to a predetermined decryption algorithm using the same fixed encryption key 24 as that of the transmitting side. Thereby, the decrypted data 25a, 25b, 25c are obtained.

As described above, by using the same fixed encryption keys 21 and 24 on the transmitting side and the receiving side, communication data can be encrypted and transmitted / received.

[0007]

However, in the above-mentioned conventional communication method, since the fixed encryption keys 21 and 24 are used for encryption and decryption, the contents of communication data are several kinds such as a command. If the data is stylized, the encrypted data will also be stylized. Therefore, there may be a case where the content of the communication data can be grasped without knowing the content of the encryption key itself.

In order to prevent this, a method of changing the contents of the encryption key at an appropriate time interval is used. However, since such a change is usually performed at a long time interval of several days or months, communication contents may be leaked during that time. Also, when changing the encryption key,
Since it is necessary to notify all terminal devices of the changed encryption key, it is troublesome to change the encryption key frequently.

An object of the present invention is to provide a communication device and a communication method capable of reliably preventing leakage of communication contents by dynamically changing an encryption key without requiring a complicated procedure. It is to be.

[0010]

Means for Solving the Problems (1) First Invention A communication device according to the first invention comprises a time measuring means for measuring time,
Rounding means for rounding the value of the timekeeping means to an arbitrary precision, encryption means for encrypting the transmission data using the encryption key based on the value obtained by the rounding means, and encrypted data obtained by the encryption means , A receiving means for receiving the encrypted data, a decrypting means for decrypting the encrypted data received by the receiving means by using the encryption key based on the value obtained by the rounding means, and a rounding amount. To determine
Rounding amount determining means .

The encryption means sends the rounding amount determination data.
Sometimes, rounding means rounds the value to multiple levels of precision.
Data using multiple encryption keys
And, sending the data rounding amount determining multiple encrypted data
Transmit via communication means. The decoding means is a
When receiving data, it is rounded to multiple levels of precision by the rounding means.
Received with multiple encryption keys based on the assigned value
Decrypt the rounding amount determination data. The rounding amount determining means
Based on the decoding result of the rounding amount determination data by the reading means
Determine the amount of rounding.

(2) Second Invention A communication method according to the second invention is to send rounding amount determination data.
At the time of delivery, multiple values based on rounded values
The transmitted data is encrypted using the encryption key, and multiple encrypted
The converted data is sent as data for determining the rounding amount, and the rounding amount is determined.
Value rounded to multiple levels of accuracy when receiving regular data
Rounding received with multiple encryption keys based on
Decode the regular data and use it as the decryption result of the rounding amount determination data.
The amount of rounding is determined based on the rounded value of the timekeeping means to the precision corresponding to the determined amount of rounding when the data is sent, and the data is encrypted using the encryption key based on the rounded value and sent. When data is received, the value of the timer is rounded to the above precision, and the received data is decrypted using an encryption key based on the rounded value.

[0013]

In the communication device according to the first invention and the second invention,
In such a communication method , the value of the timekeeping means is rounded to an arbitrary precision, the transmitted data is encrypted using the encryption key based on the rounded value when transmitting the data, and the rounding is performed when receiving the data. The encrypted data is decrypted using the encryption key based on the obtained value.

In this way, on the transmitting side and the receiving side, the data is encrypted and decrypted by using the encrypted data which are dynamically changed and synchronized with each other. Thereby, even if the communication content is standardized, the encrypted data to be transmitted constantly changes dynamically. Therefore,
It is possible to reliably prevent the leakage of communication contents without requiring a complicated procedure.

In addition, even if there is an error in the value of the clock means between the transmitting side and the receiving side, the receiving side can accurately obtain the decoded data corresponding to the transmitted data.

Particularly , when transmitting the rounding amount determination data, the transmission data is encrypted using a plurality of encryption keys based on the values rounded to a plurality of levels of precision, and the plurality of encrypted data are used for the rounding amount determination. Sent as data. Further, when the rounding amount determination data is received, the received rounding amount determination data is decrypted by using the plurality of encryption keys based on the values rounded to a plurality of levels of accuracy. Then, the rounding amount is determined based on the decoding result of the rounding amount determination data.

Thus, before the actual data communication,
By exchanging the rounding amount determination data between the sending side and the receiving side, the minimum rounding that can accurately decrypt the encrypted data when there is an error in the value of the time measuring means between the sending side and the receiving side. The amount can be determined. Therefore, it is possible to perform accurate data communication while surely preventing the leakage of communication contents according to the error of the value of the time measuring means on the transmitting side and the receiving side.

[0018]

1 is a diagram showing a communication method according to a first embodiment of the present invention. In this embodiment, the value of the internal timer is used as the encryption key on the transmitting side and the receiving side.

On the transmitting side, the value of the internal timer is 199.
When it is 18:00 on October 17, 4th, "19
Transmission data 2 according to a predetermined encryption algorithm using the encryption key 1a having the value of "94101718".
a, 2b, and 2c are encrypted. Thereby, the encrypted data 3a, 3b, 3c are obtained and transmitted to the receiving side.
Further, when the value of the internal timer indicates 19:00 on October 17, 1994, the transmission data 2a, 2b, 2c are transmitted according to a predetermined encryption algorithm using the encryption key 1b having the value "1994101719". Encrypted. Thereby, the encrypted data 4a, 4b, 4c is obtained and transmitted to the receiving side.

As described above, even if the transmission data is the same, the content of the encrypted data dynamically changes depending on the time of encryption.

On the other hand, on the receiving side, the value of the internal timer is 19
When it is 18:00 on October 17, 1994, "1
The received encrypted data 3a, 3b, 3c is decrypted according to a predetermined decryption algorithm using the encryption key 5a having a value of "994101718". Thereby, the decrypted data 6a, 6b, 6c is obtained. When the value of the internal timer indicates 19:00 on October 17, 1994, the received encrypted data 4a, 4b, 4c is decrypted. Thereby, the decrypted data 6a, 6b, 6c is obtained.

As described above, by using the value of the internal timer as the encryption key, the encryption key changes dynamically, and decryption data matching the transmission data can be obtained on the receiving side.

FIG. 2 is a diagram showing a communication method according to the second embodiment of the present invention. In the present embodiment, the value obtained by rounding the value of the internal timer on the transmitting side and the receiving side by the set rounding width is used as the encryption key.

Here, it is assumed that there is a one-hour error between the value 11 of the internal timer on the transmitting side and the value 17 of the internal timer on the receiving side.

On the transmitting side, the value 11 of the internal timer is set to a plurality of rounding widths 13a, 13b, 13c, which are set in stages.
Rounded at 13d. Rounding width 13a is the internal timer value 1
1 means rounding the lower 4 digits, rounding width 13b means rounding the lower 3 digits of the internal timer value 11, rounding width 13c means rounding the lower 2 digits of the internal timer value 11. However, the rounding width 13d means that the lower 1 digit of the value 11 of the internal timer is rounded.

When the value 11 of the internal timer indicates 18:05 on October 17, 1994, the rounding width 13a gives the encryption key 14a having the value "941017", and the rounding width 13b gives "9410171". An encryption key 14b having a value of "" is obtained. In addition, rounding width 13c
Encryption key 1 having a value of "94101718" by
4c is obtained, and the rounding width 13d causes "94101718".
An encryption key 14d having a value of "0" is obtained.

Using the plurality of encryption keys 14a, 14b, 14c, 14d thus obtained, the rounding width setting data 12 is encrypted according to a predetermined encryption algorithm. Thereby, a plurality of encrypted data 15a,
15b, 15c and 15d are obtained. These encrypted data 15a, 15b, 15c, 15d are combined and transmitted as the encryption code 16 for setting the rounding width.

On the receiving side, the value 17 of the internal timer is the same as that on the transmitting side.
It is rounded by 8b, 18c and 18d. The rounding width 18a means that the lower 4 digits of the internal timer value 17 are rounded, the rounding width 18b means that the lower 3 digits of the internal timer value 17 are rounded, and the rounding width 18c is the internal timer value 17 of the internal timer value 17. This means that the lower 2 digits are rounded, and the rounding width 18d means that the lower 1 digit of the value 17 of the internal timer is rounded.

When the value 17 of the internal timer indicates 19:05 on October 17, 1994, the rounding width 18a gives the encryption key 19a having the value "941017", and the rounding width 18b gives "9410171". An encryption key 19b having a value of "" is obtained. In addition, rounding width 18c
Encryption key 1 having a value of "94101719" by
9c is obtained, and with the rounding width 18d, "94101719"
An encryption key 19d having a value of "0" is obtained.

Using the plurality of encryption keys 19a, 19b, 19c and 19d thus obtained, the received encryption code 16 for setting the rounding width is decrypted according to a predetermined decryption algorithm. Thereby, the decrypted data 20
a, 20b, 20c, 20d are obtained. By comparing these decrypted data 20a, 20b, 20c, and 20d with known rounding width setting data, the optimum rounding width can be obtained on the transmitting side and the receiving side.

In the example of FIG. 2, the transmission data 1 is transmitted using the encryption keys 14a and 14b obtained with the rounding widths 13a and 13b.
Only when 2 is encrypted, the correct decryption data 2 on the receiving side
0a and 20b are obtained. That is, when there is an error of one hour between the value 11 of the internal timer on the transmitting side and the value 17 of the internal timer on the receiving side, in order to correctly decrypt the encrypted data on the receiving side, the transmitting side and the On the receiving side, the rounding widths 13b and 18b are determined to be the minimum rounding widths, respectively.

After that, the transmission side encrypts the transmission data using the encryption key 14b with the rounding width 13b,
The reception side decrypts the received encrypted data using the encryption key 19b having the rounding width 18b.

FIG. 3 is a functional block diagram showing the structure of a communication device for executing the communication method of FIG.

In the communication device 100 of FIG. 3, the internal timer 31 measures the current time. The rounding width setting means 32 includes a plurality of dividers 32a, 32b corresponding to a plurality of rounding widths.
32c and 32d. Dividers 32a, 32b, 32
Stepwise rounding widths are set in c and 32d, respectively.
Each of the dividers 32a, 32b, 32c, and 32d rounds the value of the internal timer 31 by dividing the value of the internal timer 31 by the set rounding width. Encryption key setting unit 33
Sets the value rounded by each of the dividers 32a, 32b, 32c, 32d as an encryption key.

During the rounding width setting process, the encryption / decryption unit 35 uses a plurality of encryption keys set in the encryption key setting unit 33 according to a predetermined encryption algorithm to set a preset rounding width. Data is encrypted and a plurality of encrypted data is stored in the transmission buffer 36. The plurality of encrypted data stored in the transmission buffer 36 are combined and transmitted as an encryption code for setting the rounding width.

Further, when the encryption / decryption unit 35 receives the encryption code for setting the rounding width via the receiving buffer 37 during the rounding width setting processing, the encryption / decryption unit 35 sets a plurality of encryption codes set in the encryption key setting unit 33. The received encryption code for setting the rounding width is decrypted according to a predetermined decryption algorithm using the encryption key, and a plurality of decrypted data are stored in the received data storage memory 38.

The optimum rounding width determination unit 39 determines the optimum rounding width by comparing the plurality of pieces of decoded data stored in the received data storage memory 38 with the known data for setting the rounding width, and determines the determined optimum rounding width. Is sent to the encryption / decryption unit 35 and the transmission buffer 36 stores the optimum rounding width data.
To the communication device of the other party via.

After that, the encryption / decryption unit 35 uses the encryption key obtained by the determined rounding width among the encryption keys set in the encryption key setting unit 33 at the time of data transmission, to transmit data. The transmission data stored in the storage memory 34 is encrypted. Also, the encryption / decryption unit 35, when receiving the data, decrypts the received data using the encryption key obtained by the determined rounding width among the encryption keys set in the encryption key setting unit 33. Then, the decoded data is stored in the received data storage memory 38.

The communication device shown in FIG. 3 can be realized by hardware, can be realized by software, and can be realized by both hardware and software.

FIG. 4 is a sequence diagram showing communication processing in the communication system using the communication device 100 of FIG.

First, the transmitting communication device transmits an encryption code for setting the rounding width to the receiving communication device (step S).
1). The reception-side communication device performs rounding width setting processing based on the received encryption code, determines the optimum rounding width (step S2), and notifies the transmission side communication device of the rounding width data indicating the determined rounding width. (Step S3).

After that, the transmission side communication device performs the encryption process of the transmission data using the encryption key obtained by the determined rounding width (step S4), and the obtained encrypted data is processed by the reception side communication device. (Step S5). The receiving-side communication device performs decryption processing of the encrypted data using the encryption key obtained by the determined rounding width to obtain decrypted data (step S6).

Further, the receiving side communication device performs the encryption process of the transmission data using the encryption key obtained by the determined rounding width (step S7), and transmits the encrypted data to the transmitting side communication device. (Step S8). The transmitting communication device performs decryption processing of the received encrypted data by using the encrypted data obtained by the determined rounding width, and obtains decrypted data (step S9).

Thus, before the actual data communication,
By exchanging rounding width setting data between the transmitting side and the receiving side, the optimal rounding width is set according to the error in the value of the internal timer in the transmitting side communication device and the receiving side communication device. Data is encrypted and decrypted using the encryption key with the set rounding width. Therefore, it is possible to reliably prevent the leakage of communication contents and absorb the error in the value of the internal timer to perform accurate data communication.

[0045]

According to the first and second aspects of the present invention, on the transmitting side and the receiving side, data encryption and decryption are performed using encrypted data which are dynamically changed and synchronized with each other, and the encryption is performed. Since the encrypted data constantly changes dynamically, it becomes difficult for a third party to decrypt the encrypted data. Therefore, it is possible to reliably prevent the leakage of communication contents without requiring a complicated procedure.

In particular , since the value of the time measuring means is rounded to an arbitrary precision and the encryption key based on the rounded value is used, even if there is an error in the value of the time measuring means on the transmitting side and the receiving side, an error is generated. It becomes possible to absorb, and the encrypted data can be accurately decrypted on the receiving side.

Further , since the minimum rounding amount that enables accurate data communication is determined before the actual data communication, the content of communication is leaked according to the error of the value of the time measuring means on the transmitting side and the receiving side. It is possible to perform accurate data communication while surely preventing this.

[Brief description of the drawings]

FIG. 1 is a diagram showing a communication method according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a communication method according to a second embodiment of the present invention.

3 is a functional block diagram showing the configuration of a communication device for executing the communication method of FIG.

FIG. 4 is a sequence diagram showing communication processing in a communication system using the communication device of FIG.

FIG. 5 is a block diagram showing a communication system including a plurality of terminal devices connected by a network.

FIG. 6 is a diagram showing a conventional communication method using a fixed encryption key.

[Explanation of symbols]

1a, 1b, 5a, 5b, 14a, 14b, 14c, 1
4d, 19a, 19b, 19c, 19d Encryption key 2a, 2b, 2c, transmission data 3a, 3b, 3c, 4a, 4b, 4c, 15a, 15
b, 15c, 15d Encrypted data 6a, 6b, 6c, 20a, 20b, 20c, 20d
Decoded data 11,17 Internal timer value 12 Rounding width setting data 13a, 13b, 13c, 13d, 18a, 18b, 1
8c, 18d Rounding width 16 Encryption code for setting rounding width 31 Internal timer 32 Rounding width setting unit 33 Encryption key setting unit 35 Encryption / decryption unit 39 Optimal rounding width determination unit 100 Communication device

Continuation of the front page (56) Reference JP-A 63-161745 (JP, A) JP-A 1-212041 (JP, A) JP-A 5-41704 (JP, A) JP-A 5-304614 (JP , A) Shin Ichimatsu "Mathematics of Cryptography" Bluebacks B-421, Kodansha (March 20, 1980), p. 108 Transistor Technology Editor, “Practical Electronic Circuit Handbook (2),” CQ Publishing (October 20, 1975), p. 170

Claims (2)

(57) [Claims] 1. A cipher for encrypting transmission data using a time measuring means for measuring time, a rounding means for rounding the value of the time measuring means to an arbitrary precision, and an encryption key based on the value obtained by the rounding means. Encrypting means, transmitting means for transmitting the encrypted data obtained by the encrypting means, receiving means for receiving the encrypted data, and receiving by using an encryption key based on the value obtained by the rounding means. Decryption means to decrypt the encrypted data received by the means, and determine the rounding amount
Rounding amount determining means for storing the rounding amount determining data.
Based on the value rounded to multiple levels of precision by the rounding means.
Data to be encrypted by using multiple encryption keys.
Number of encrypted data is sent as data for rounding amount determination
And the decoding means receives the rounding amount determination data upon receiving the rounding amount determination data.
Based on values rounded to multiple levels of precision by rounding means
The rounding amount determination data received using multiple encryption keys.
Data, and the rounding amount determining means determines the rounding amount by the decrypting means.
A communication device, wherein a rounding amount is determined based on a result of decoding the determination data . 2. A plurality of stages when transmitting the rounding amount determination data.
Uses multiple encryption keys based on rounded values to floor precision
Encryption of transmitted data and rounding of multiple encrypted data
Send as the data for determining the amount and receive the data for determining the rounding amount.
At the time of delivery, the number of duplicates based on the value
Rounding amount determination data received using a number of encryption keys
Based on the decoding result of the rounding amount determination data
Determine the rounding amount, and when transmitting the data, set the value of the timekeeping means.
Rounding to a precision corresponding to the determined rounding amount, encrypting and transmitting data using an encryption key based on the rounded value, when receiving data, rounding the value of the clocking means to the precision, A communication method characterized by decrypting received data using an encryption key based on the rounded value.