JPS63161745A - Terminal equipment for cryptographic communication - Google Patents

Abstract

PURPOSE:To prevent reduction in data transmission efficiency from being caused by outputting a data cryptographic key from a common key and a time latch value, ciphering a communication plain text and outputting a data decoding key from the common key and the time latch to decode the received cryptographic key. CONSTITUTION:A trigger message generator 23 generating a trigger signal message when a communication session is started, a timer 17 giving data time information, a time latch 19 latching it by the trigger message, and a ciphering device 21 are provided to give the same data time information to two terminal equipments by the trigger signal message and the data cryptographic key is provided in common between two terminal equipments by using the common key KC. Thus, every time one communication session of the ciphering data communication is applied, the request of a data cryptographic key KS is not required to the key delivery center and the data transmission efficiency is not lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an encrypted communication terminal device that performs encrypted data communication between terminals.

When encrypted data communication is performed between terminals using a conventional encryption method, it is necessary to update the data encryption key shared between the terminals for each communication session in order to guarantee the security of the encryption key.

Conventionally, the encryption key distribution method in conventional cryptography is as follows:
A centralized key management method is known in which a key distribution center is set up to manage the unique terminals of each terminal, generate or manage data encryption keys used when transferring data between each terminal, and deliver them to each terminal. .

An example of such a conventional cryptographic key distribution method is W.

“Security for Computer Networks” by D.W. DAVIS and W.L. Price.
AND W, L, PRICE; 5ECURITY FO
RCOMPUTERNETWORKS, JOHN W.
ILEY&5ONS) f shown.

FIG. 2 shows a protocol diagram of a cryptographic key distribution system using this conventional centralized key management system.

In Figure 2, 1 is a terminal A that plays a leading role in the distribution of encryption keys and has KA as a terminal key, 2 is a terminal B that has KB as a terminal pair, and 3 is a terminal unique to each terminal. This is a key distribution center that manages pairs of terminals, generates or manages data encryption keys used when transferring data between each terminal, and distributes them to each terminal. KA and KB are respectively terminal A
, is the secret key of terminal B and is known only to you and the key distribution center.

In the conventional encryption key distribution system configured as described above, a protocol for delivering and authenticating the data encryption key KS for secretly encrypted data communication between terminal A and terminal B will be described.

In the following explanation, the message X is written as EK(X) in the ciphertext encrypted with gsK.

[1] Terminal A uses data encryption of 1m for data communication with terminal B! In order to obtain KSt-, the request REQAB to the key distribution center and the confirmation number 1d are encrypted by the terminal 'aKA of terminal A, and EKA(REQAB-1d) (1
) and send it to the key distribution center.

Here, the confirmation number 1d is a random number created by terminal A, and is used to confirm that the message has not been tampered with on the way and that the eavesdropper has not retransmitted what was previously eavesdropped.

[2] The key distribution center decrypts the above ciphertext (1), and based on this, sends the data encryption key KS, confirmation number 1d, data encryption fiKs, and identifier A of terminal A to terminal A to terminal B. The ciphertext EKA (K S, i d,
Send EKB(K S, A)) (2).

[3] Terminal A checks the ID from the above ciphertext (2) and data encryption faKSI! 'EKB(KS,A
) and hold it. After that, EKB (KS, A) and EKs (X) obtained by encrypting the random number X with KS are transmitted to terminal B. This ciphertext is written as follows.

E KB (K S p A) e E Ks (X) ---
(3) Here, Ell(X) is used to check whether the data encryption key KS has been correctly transmitted to the terminal B.

[41m end B is EKB (KS, A) in the above ciphertext (3)
), it recognizes that it is an official data communication request from terminal A via the key distribution center, and extracts and holds the data encryption key KS.

Further, Egs(X) in the above ciphertext (3) is decrypted by this KS to obtain a random number X, and F(X) is generated using a predetermined number F. This is encrypted with KS and sent to terminal A as EKs(F (X)) - (4).

[5] Terminal A decrypts the above ciphertext (4) and obtains F(X
), and by checking whether it is generated by the random number X and the random number F, it can be confirmed that the data encryption key KS has been correctly transmitted to the terminal B. In this way, terminal A and terminal B can share the data encryption @IKs necessary for encrypted data communication, and in subsequent data communication, encrypted communication will be performed using this data encryption key KS. be able to.

Next, the configuration of a terminal used in the conventional centralized key management method as shown above will be explained below.

FIG. 3 shows a block diagram of a terminal used in such a conventional centralized key management system. In Fig. 3, 1 plays a leading role in the generation of encryption keys, and K serves as a terminal pair.
Terminal A with A, 2 is terminal B with KB as a terminal pair,
4 is a communication line, and 5 and 6 are data buffers at the terminal A1 terminal port, respectively, through which plain text messages are input and output. 7
is an encryption/decryption device of terminal A, 8 is an encryption/decryption device of terminal B, 9 is a terminal key register that stores the terminal pair KA of terminal A, and 10 is a terminal key register that stores the terminal pair KB of terminal B. , 11 and 12 are data encryption key registers that store a common data encryption key KS in terminal A and terminal B, respectively;
3 is a random number generator within terminal A, which generates the confirmation number 1d and random number X shown in the above protocol. Numerals 14 and 15 are located in terminal A and terminal B, respectively, and execute a predetermined number F, and 16 is a comparator that compares the output of the encryption/decryption device 7 with the output of the function generator 14. .

The operation of the terminal configuration in the conventional cryptographic key distribution system configured as described above will be described below.

If terminal A has a plaintext message to be encrypted and transmitted, it prepares it in data buffer 5. The encryption/decryption device 7 uses the value of the terminal key register 9 as a key when manually encrypting the contents of the data buffer 5 or the random number generator 13 with the terminal key KA, and uses the value of the terminal key register 9 as the key when encrypting the contents with the data encryption filKs. Encryption is performed using the value of the key register 11 as a key, and the encrypted text is output to the communication line 4. Furthermore, the encrypted message received from the communication line 4 is similarly decrypted in the encryption/decryption device 7 using the value of the terminal key register 9 or the data encryption key register 11 as a key, and the decrypted message is written to the data buffer 5. It will be done.

The same is true for terminal B, and if there is a plaintext message to be encrypted and transmitted, it is prepared in the data buffer 6. The encryption/decryption device 8 uses the value of the terminal key register 10 as a key when encrypting with the terminal key KB manually.
When encrypting data using the data encryption UKS, the value of the data encryption pair register 12 is used as a key to execute the encryption, and the encrypted text is output to the communication line 4. Similarly, the encrypted message received from the communication line 4 is sent to the terminal key register 10 or the data encryption key register 11 in the encryption/decryption device 8.
The message is decrypted using the value as a key, and the decrypted message is written to the data buffer 6.

The operation of checking the coincidence of the data encryption key KS between the terminals A and B using the random number X shown in the above protocols [3] to [5] will be described below.

The random number X generated by the random number generator 13 is sent to the function unit 14
is input manually, and is encrypted by the encryption/decryption device 7 with the value KSA of the data encryption key register 11, resulting in the ciphertext E.
KSA(X) is sent to terminal B via communication line 4.

At terminal B, EKSA(X) is decrypted by the encryption/decryption device 8 using the value KSB of the data encryption key register 12. If terminal A's data encryption key register 11 value K
If the value KSB of the data encryption key register 12 of SA and terminal B match, the decryption result is a random number X. This is input to the function unit 15, and its output F(X) is encrypted by the encryption/decryption device 8 with a data encryption of 1KsB, and the ciphertext EKss (F (X) ) is sent to the terminal A through the communication line 4. EK8B (F
(X)) is the data encryption key K by the encryption/decryption device 7.
sA, and the comparator 16 compares the decoded value with the output F(X) of the function unit 14.

If these are the same, the data encryption key register 11 of terminal A
value KSA and the value K of the data encryption key register 12 of terminal B
It is found that the SBs match, and this can be used as the data encryption key in one subsequent communication session of encrypted data communication.

If the comparison results in the comparator 16 are not the same, a common data encryption WKS must be obtained again using the protocols [1] to [5] above.

As described above, terminal A and terminal B can share the data encryption key KS necessary for encrypted data communication, and in one communication session of subsequent data communication, this data encryption key 11Ks is used. Encrypted communication can be performed.

Problems to be Solved by the Invention However, in the above method, it is necessary to request data encryption WKS from the key distribution center before each communication session of encrypted data communication between terminals. In addition, when the frequency of access increases between some terminals, access contention tends to occur and data transmission efficiency decreases. Another problem is that if the same data encryption key is used for a long time in one communication session, the security of the key is compromised.

In view of the above, the present invention provides an encryption key that reduces the number of access requests for data encryption keys to a key distribution center without compromising the security of the data encryption keys, and provides efficient data transmission in encrypted communications between terminals. The purpose is to provide a delivery method.

Means for Solving the Problems The present invention provides an encryption device for encrypting data to be communicated;
A decryption device that decrypts encrypted data received from a communication line, a common key register that stores a common key agreed upon in advance with a communicating party terminal, a timer that provides current date and time information, and a time that latches the timer value. a latch, a data encryption key output circuit that outputs a data encryption key based on the values of the common key and the time latch, and a trigger signal message generator that generates a latch trigger to the time latch and outputs a trigger signal message through a communication line. , a terminal device for encrypted communication comprising a trigger signal message detector that detects a received trigger signal message and outputs a latch signal to the time latch at the time of detection.

According to the above-described configuration, the trigger signal message generator in the first terminal generates a trigger to the time latch at the start of one communication session, so that the time latch latches the date and time information of the timer, and the communication starts. Outputs a trigger signal message through the line. A trigger signal message detector at the second terminal receives and detects this and generates a trigger to the time latch, which causes the time latch to latch the date and time information of the timer. A data encryption key output circuit in the first terminal outputs a data encryption key based on the values of the common pair and the time latch, and using this as a key, the encryption device encrypts communication plaintext data and sends it to the communication line.

A data encryption key output circuit in the second terminal outputs a data decryption key based on the common key and the value of the time latch, and using this as a key, the decryption device decrypts the ciphertext of the first terminal received from the communication line.

Embodiment Regarding the encryption key distribution method in the embodiment of the present invention, the protocol will be explained below for the case where encrypted data communication is performed between terminal A, which plays a leading role in the distribution of encryption keys, and another terminal. .

[1] A common key KC is obtained between terminal A and terminal B using a centralized key management system in which a key distribution center is installed, using the protocol described in the conventional example above.

[2] When starting one session of data communication, at the starting point, terminal A latches the current date and time information TA and sends a trigger signal message to terminal B via the communication line. Terminal B detects this trigger signal message and similarly latches the date and time information TB at that time.

[3] It is necessary to check whether the date and time information TB latched at terminal B is the same as the date and time information TA latched at terminal A. For this purpose, terminal A encrypts the date and time information TA using a common IKc and encrypts the ciphertext E.
The random number X is encrypted as KC(TA) = ETA t' fla, and EETA(X) is sent to terminal B.

At terminal B, the date and time information TB is encrypted using the common fiKc into a ciphertext E. EETA(X) received as (TB)=ETBtr:fi is decoded, and if TA and TB match, random number X is obtained. F(X) is generated using the prearranged open number F1t', which is encrypted with ETB and sent to terminal A as EETB(F(X)).

At terminal A, the above ciphertext EETB(F(X)) is ETA
is decoded to obtain F(X), which is compared with F(X) calculated using random number X and open number F to determine TA and TB.
You can check that they match.

[4] In this way, terminal A and terminal B can share EKC(T) obtained by encrypting date and time information T using the common fiKc as a data encryption key necessary for encrypted data communication,
In one communication session in subsequent encrypted data communication, encrypted communication is performed using this data encryption fa7f:.

[5] To obtain the data encryption key necessary for the next communication session and use it to perform encrypted communication, repeat [2]
The operations [21 to 4] are continued while the data communication of the application data block including multiple communication sessions is performed. Therefore, in order to perform such multiple communication sessions, the operations [21 to [4] are performed. There is no need for terminal A to access the key distribution center and obtain the common key.

[6] It is preferable to communicate with another application data block by changing the common key KC as well.

In this case, the protocols from [1] to [5] above are repeated.

Next, the above operation will be explained by showing the circuit blocks of a specific terminal.

FIG. 1 shows a block diagram of a terminal used in the cryptographic key distribution system in the above embodiment of the present invention. In FIG. 1, 1 is a terminal A that plays a leading role in generating encryption keys and has KA as a terminal pair, 2 is a terminal B that has KB as a terminal pair, 4 is a communication line, 5 and 6 are terminals A, This is the data buffer of terminal B, and plain text messages are output. 7 is an encryption/decryption device of terminal A, 8 is an encryption/decryption device of terminal B, 9 is a terminal key register that stores the terminal pair KA of the terminal user, and 10 is a terminal key that stores the terminal pair KB of terminal B. Registers 11 and 12 are terminal A and terminal B, respectively.
13 is a random number generator in terminal A, 14 and 15 are in terminal A and terminal B, respectively, and are number counters that execute a predetermined function F.
A comparator 16 compares the output of the encryption/decryption device 7 and the output of the interpolator 14. 17 and 18 are timers that give current date and time information, and 19 and 20 are timers 17 and 1, respectively.
8 is the time latch that latches the value, 21 is the time latch 19
22 is an encoder that encrypts the value of the time latch 20 with the content KC of the common key register 12. 23 is an encoder when starting one session of data transfer. A trigger signal message generator 24 generates a trigger indicating the start of data transfer and applies it to the time latch 19, and outputs a trigger signal message indicating the start of data transfer to the destination terminal via the communication line 4. FIG. 2 is a block diagram of a terminal used in a conventional key management method in 0 or more blocks that are trigger signal message detectors that detect a trigger signal message received from another terminal and output a latch signal to a time latch 20 upon detection. Blocks with the same numbers as in FIG. 3 basically perform the same operations.

The operation of the encryption key distribution system of this embodiment configured as described above will be described below with respect to the case where terminal A and terminal B perform encrypted data communication in the dark.

Using the protocol described in the conventional example using a centralized key management system with a key distribution center, terminal A and terminal B obtain the common key KC in the dark, and store the common key registers 11 and 12 respectively.
Store in.

When performing one communication session of encrypted data communication, the trigger signal message generator 23 of the terminal A1 outputs a latch signal to the time latch 19 at the time when data communication is started, and also sends a communication session signal to the terminal B via the communication line 4. Sends a trigger signal message instructing the start. As a result, the time latch 19 of terminal A is set to timer 1.
The date and time information TA indicated by 7 is latched. Further, the trigger signal message detector 24 of terminal B detects this trigger signal message and outputs a latch signal to the time latch 20 at the time of detection. As a result, the time latch 20 latches the current date and time information TB indicated by the timer 18. Since the timers 17 and 18 each operate in units of a certain time width (for example, minutes or seconds) that is sufficiently long compared to the delay time of the communication line 4, the time latch 1 at terminal A
The value TA of timer 17 when time latch 9 latches and the value TB of timer 18 when time latch 20 latches at terminal B.
are often the same. (In principle, the value TB of the timer 18 when the time latch 20 latches in the terminal B is different from the time latch 1 in the terminal A due to a delay in the communication line 4, etc.)
It is possible that timer 9 is ahead of the latched value TA of timer 17 by one time width unit).

At terminal A, the encoder 21 encrypts the value of TA using the content KC of the common key register 11 as a key, and EKC(TA)=E.
Output TA. The encryption/decryption device 7 is a random number generator 13
The output X is encrypted using ETA as a key, and E and TA(X) are sent to terminal B through the communication line 4. Also in terminal B, the encoder 22 encrypts the value of TB using the content KC of the common key register 12 as a key, and EKC(T B) = E T B
Output. Encryption/decryption device 8 decrypts EETA(X) received from terminal A using ETB as a key. If TB is equal to TA, random number X is decoded. This is function unit 1
5, and the output F(X) is sent to the encryption/decryption device 8.
It is encrypted using TB as a key and sent to terminal A via communication line 4 as EETB (F(X)). In the terminal A, the encryption/decryption device 7 decrypts this using the ETAt' key,
A comparator 16 compares it with the output F(X) of the interpolator 14. If they match, the value TA of time latch 19
It is confirmed that the value TB of the time latch 20 and the value TB of the time latch 20 are set to the same value. If they do not match, it is detected that the value TA of the time latch 19 and the value TB of the time latch 20 are different, and the trigger signal message generator 23 generates a trigger signal again.

If it is confirmed that TA and TB match in this way, in one communication session in subsequent data communication, terminal A and terminal B each receive the output E of the encoder 21.
KC (TA) and the output EKC (TB) of the encoder 22
can be used as a data encryption key.

When one communication session ends and the next communication session is to be performed, the trigger signal message generator 23 generates a trigger signal again to latch the date and time information in the time latch 19 without changing the common fiKc, and the above operation is performed. This value is encrypted by the encoder 21 in the same manner as above, and the value is used as the data encryption key for the new communication session.

When an application block containing multiple communication sessions ends and encrypted communication is to be performed for the next application block, terminal A can access the key distribution center and re-obtain the next common*KC if necessary. Bye.

As described above, according to this embodiment, the trigger signal message generator 23 generates a trigger signal message when starting a communication session, and the timer 17 provides date and time information.
, a time latch 19 that latches this in response to a trigger signal message, and an encoder 21 are provided to allow two terminals to have the same date and time information in response to a trigger signal message, and use this and a common key KC to create a data encryption key. can be shared between two devices. Therefore, there is no need to request data encryption fiKs from the key distribution center before each communication session of encrypted data communication.
Therefore, even if there are many terminals, the frequency of requests for data encryption keys from the key distribution center does not increase, and data transmission efficiency does not decrease.

In addition, in the protocol example of this embodiment, is the date and time information TB latched at terminal B the same as the date and time information TA latched at terminal A, that is, the data encryption key EKC (TA) used for encrypted communication? are terminals A and B
It was confirmed whether or not they matched by using random number X and random number F (protocol description number [3])
, This confirmation adds a pre-arranged message authentication code to the transferred data, encrypts such data with this data encryption WEKC (TA) and sends it, and sends it to terminal B.
This method may be performed by decrypting and authenticating with the data encryption key EKC (TB) on the side, which simplifies the data encryption key confirmation protocol and improves transmission efficiency.

Furthermore, the data encryption key created in this embodiment is a value EKC ( TA), but this may be any number of intervals that inputs two values: the content TA of the time latch 19 and the common 1iKc.

As described in detail, according to the present invention, there is no need to request data encryption WKS from the key distribution center before each communication session of encrypted data communication between terminals. Therefore, the frequency of access from many terminals to the key distribution center does not increase, and data transmission efficiency does not decrease. Therefore, the present invention does not impair the security of data encryption keys, and the frequency of access to the key distribution center from many terminals does not increase. It is possible to provide an encryption key distribution method that reduces the number of requested accesses to data encryption keys and has high data transmission efficiency in encrypted communication between terminals, and has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an encrypted communication terminal device according to an embodiment of the present invention, Figure 2 is a protocol diagram of a conventional cryptographic key distribution system, and Figure 3 is a block diagram of a terminal device in a conventional cryptographic key distribution system. It is a diagram. 1...Terminal A, 2...Terminal B, 4...Communication line,
7, 8... Encryption/decryption device, 11゜12... Common key register, 17.18... Timer, 19.20...
- Time latch, 21.22... Encryptor, 23... Trigger signal message generator, 24... Trigger signal message generator. Name of agent: Patent attorney Toshio Nakao Haka18yan 2rX
J

Claims (1)

[Claims] An encryption device that encrypts data to be communicated, a decryption device that decrypts encrypted data received from a communication line, a common key register that stores a common key agreed upon in advance with the communication partner terminal, and current date and time information. a time latch that latches the timer value; a data encryption key output circuit that outputs a data encryption key from the common key and the value of the time latch; An encrypted communication terminal device comprising: a trigger signal message generator that outputs a trigger signal message; and a trigger signal message detector that detects a received trigger signal message and outputs a latch signal to the time latch upon detection.