JP2003244131A - Key management device, key management method, key management program, and computer readable recording medium with key management program recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus capable of switching a key so as to hardly leak the key when utilizing a common key cipher system. <P>SOLUTION: This device has a key storage region 2 for storing a plurality of cipher keys, a use key storage region 1 for storing a key itself that is currently used or an index number corresponding to the key, a communication means 4 which communicates with outside through a network such as the Internet, a key management means 5 which manages the key to be used when encrypting and changes the current key in case necessary for changing the key, a control means 10 which controls the flow of various data. The key is switched as needed. Consequently, it prevents the key from being leaked to a third parson and it is possible to improve the strength of encryption system. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records an encryption key management device, a key management method, a key management program, and a key management program capable of managing a common key used in a common key cryptosystem and appropriately changing it. Computer-readable recording medium.

[0002]

2. Description of the Related Art With the recent development of the Internet network,
There are increasing opportunities to transmit confidential data such as personal information and in-house information via the Internet.

However, the Internet is not always a safe communication path, and technically it is possible to eavesdrop on data flowing through the Internet.

Therefore, in order to prevent the data from being illegally leaked by wiretapping, an encryption technique is used for converting the data into data that cannot be seen by a third party even if the data is tapped. In recent years, an encryption method using a key has been widely used. Cryptography using a key keeps data confidential by keeping the key secret.

The key-based cryptosystems are roughly classified into a common-key cryptosystem and a public-key cryptosystem, but here, only the common-key cryptosystem will be described.

[0006] The common key cryptosystem means a text encrypted by using the same key as the key used when encrypting original data (hereinafter referred to as "plaintext") (hereinafter, "encryption"). It is an encryption method for decrypting a "text"). Since a key is required for each communication partner, as the number of communication partners increases, the number of keys also increases and the management thereof becomes complicated. Also, the key is
Prior to encrypted communication, secretly, in advance, between the correspondents,
Must be shared. As an example of such a common key cryptosystem, DES (Data Encryption)
Standard).

By the way, the encryption technique can be used not only to keep the confidentiality of the communication contents but also to authenticate the legitimacy of the communication partner. If the legitimacy of the communication partner is not guaranteed, it is possible for an unauthorized third party to impersonate a legitimate correspondent and perform impersonation. In order to prevent this, the method of using the encryption technology for partner authentication is as follows.

As an authentication method using the common key cryptosystem, there is one based on the authentication method described in the international standard ISO / IEC9798- (2). FIG. 6 shows a conceptual diagram of partner authentication using common key cryptography. This authentication method is based on proving that the prover (device to be authenticated) has a secret function called an authentication function to the authenticator (device to be authenticated) without notifying the function itself. . An encryption method is used as this authentication function.

More specifically, first, the cryptographic algorithm and the key are shared between the device on the authentication side and the device on the authentication side. Then, the authenticator first selects certain data (challenge data) and sends it to the prover. On the other hand, the prover converts the challenge data using an authentication function, and returns the obtained data (response data) to the authenticator. The authenticator receiving this response data converts the sent challenge by using the authentication function possessed by itself, and compares the result with the response data. If they match, it is determined that the other party has a legitimate authentication function (encryption algorithm and key), and the validity is verified.

If the common key is leaked to a third party for some reason, the confidentiality of the encrypted communication cannot be maintained, and the communication content is leaked to an unauthorized third party. In the case of authentication, there is a risk that a third party may impersonate a legitimate correspondent using the illegally obtained key and make an unauthorized communication. Therefore, in either case, it is necessary to change the key to continue secure communication. However, if the common key is leaked to a third party, in the case of consumer products, it takes a lot of time and cost to collect all products on the market and change the key. It must be made. Therefore, a method of holding multiple keys in advance and using some method to identify which key is used for encryption so that a key leaked to a third party is not used can be considered. Has been.

[0011]

However, in the conventional method, the key is changed only after it is discovered that the key has been leaked, and before the key is actually leaked until it is changed. , There is a possibility that important data may be leaked or unauthorized communication may be damaged due to spoofing. Further, by continuing to use the leaked key without even knowing that the key has been leaked to a third party, there is a possibility that important data may be leaked or fraudulent communication may be damaged due to spoofing.

Further, in order to prevent the leakage of the key, in the common key encryption method, it can be said that the longer the key length used, the higher the strength. Therefore, it is possible to increase the key length, but the key length is long. There is a problem that the time required for encryption or decryption becomes longer.

Therefore, an object of the present invention is to construct an encryption system having high strength without lengthening a key used for encryption or decryption.

[0014]

In a key management device of the present invention, a key storage area for storing a plurality of encryption keys and a key storage area currently used or an index number corresponding to the key is used. A key storage area, a communication means for communicating with the outside via a network such as the Internet, and a key management means for managing the key used at the time of encryption and changing the key in use when the key needs to be changed. , And a control means for controlling the flow of various data.

According to the present invention, it is possible to obtain a key management device in which the key can be changed periodically, and it is difficult to obtain the key illegally.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention stores a key storage area for storing a plurality of encryption keys and the key itself currently used or an index number corresponding to the key. A key storage area, a communication means for communicating with the outside via a network such as the Internet, and a key management means for managing the key used at the time of encryption and changing the key in use when the key needs to be changed. And a control means for controlling the flow of various data. The key management device is characterized in that the key can be changed as necessary, and the product can be recovered for the key change. This has the effect of reducing the cost required for.

According to a second aspect of the present invention, there is provided a key change time storage area for storing a key change time, a current time obtaining means for obtaining the current time, and a last update time of the key stored in the key change time storage area. , Referring to the current time acquired by the current time acquisition means, and if a fixed time has passed since the last key change,
The key management device according to claim 1, further comprising a key management means for changing the key. The key management device is capable of changing the key at regular time intervals, thereby increasing the strength of the encryption system. Have.

According to a third aspect of the present invention, a random number generating means for generating a random number and the presence or absence of a key change are determined based on the random number generated by the random number generating means, and the key or the index number corresponding to the key is used as the key to be used. The key management device according to claim 1 or 2, further comprising a key management means for storing in a storage area, wherein the key is changed every communication, and the strength of the encryption system is further increased. Have an effect.

According to a fourth aspect of the present invention, a key having a key storage area for storing a plurality of encryption keys and a key storage area for storing the currently used key itself or an index number corresponding to the key Key storage that manages the key used during encryption for the management device, and changes the key in use when it is necessary to change the key and the key storage that stores the changed key itself or the index number corresponding to the key The key management method is characterized by having a key selection step including steps and a communication step of performing communication with the outside via a network such as the Internet, and the key can be changed as necessary. Therefore, there is an effect that it is possible to reduce the cost required for collecting the product for changing the key.

According to a fifth aspect of the present invention, the key management device is provided with a key change time storage area for storing the key change time, and the key selecting step includes a current time obtaining step for obtaining the current time and a key changing step. In the key change time acquisition step that acquires the last update time of the key stored in the time storage area, the current time acquisition step that acquires the current time, and the key change time acquired in the key change time acquisition step, and the current time acquisition step 5. The key management method according to claim 4, further comprising a key management step of changing the key when a predetermined time has elapsed since the last key change with reference to the acquired current time. The key can be changed at regular intervals, which has the effect of increasing the strength of the cryptographic system.

According to a sixth aspect of the present invention, the key selection step includes a random number generation step for generating a random number, and a key change step for determining whether or not there is a key change based on the random number generated in the random number generation step. The key management method according to claim 4 or 5, wherein the key is changed each time communication is performed, and the strength of the encryption system is further enhanced.

According to a seventh aspect of the present invention, a key having a key storage area for storing a plurality of encryption keys and a key storage area for storing the currently used key itself or an index number corresponding to the key Key storage that manages the key used during encryption for the management device, and changes the key in use when it is necessary to change the key and the key storage that stores the changed key itself or the index number corresponding to the key It is a key management program for executing a key selection step including steps and a communication step for executing communication with the outside via a network such as the Internet.Because the key can be changed as necessary, This has the effect of reducing the cost required for product recovery and the like due to the key change.

According to an eighth aspect of the present invention, the key management device is provided with a key change time storage area for storing a key change time, and the key selecting step includes a current time obtaining step for obtaining the current time, and a key changing step. In the key change time acquisition step that acquires the last update time of the key stored in the time storage area, the current time acquisition step that acquires the current time, and the key change time acquired in the key change time acquisition step, and the current time acquisition step The key management program according to claim 7 for executing the key management step of changing the key when a predetermined time has elapsed since the last key change with reference to the acquired current time. The key can be changed every time, which has the effect of increasing the strength of the cryptographic system.

According to a ninth aspect of the present invention, the key selecting step includes a random number generating step for generating a random number, and a key changing step for determining whether or not a key is changed based on the random number generated in the random number generating step. The key management program according to item 7 or 8 has the function of changing the key each time communication is performed and further increasing the strength of the cryptographic system.

According to a tenth aspect of the present invention, a key having a key storage area for storing a plurality of encryption keys and a key storage area for storing the key itself currently used or an index number corresponding to the key Key storage that manages the key used during encryption for the management device, and changes the key in use when it is necessary to change the key and the key storage that stores the changed key itself or the index number corresponding to the key A computer-readable recording medium recording a key management program for causing a computer to perform a key selection step including steps and a communication step for performing communication with the outside via a network such as the Internet. The key management program according to claim 7 can be easily realized.

According to an eleventh aspect of the present invention, the key management device is provided with a key change time storage area for storing the key change time, and the key selecting step is the final step of the key stored in the key change time storage area. Refer to the key change time acquisition step to acquire the update time, the current time acquisition step to acquire the current time, and the key change time acquired in the key change time acquisition step, and the current time acquired in the current time acquisition step If a certain time has passed since the key was changed,
A computer-readable recording medium recording the key management program according to claim 10 having a key management step of changing a key, and the key management program according to claim 8 can be easily realized. Has the effect of.

According to the twelfth aspect of the invention, the key selecting step includes a random number generating step for generating a random number, and a key changing step for determining whether or not a key is changed based on the random number generated in the random number generating step. Item 10 or 1
The key management program according to claim 1 is a computer-readable recording medium, and has an effect that the key management program according to claim 9 can be easily realized.

FIG. 1 shows an embodiment of the present invention.
It will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a functional block diagram of a key management apparatus according to an embodiment of the present invention, showing a configuration of functional means.

In FIG. 1, reference numeral 1 denotes a used key storage area for storing a key itself to be used or an index number corresponding to the key to be used when the present encryption system is used.
Reference numeral 2 is a key storage area for storing a plurality of secret keys, 3 is a key change time storage area for storing the time when the key was last changed, 4 is communication means for executing communication with the outside through a network such as the Internet, and 5 Is a key management means for managing the key used for encryption stored in the used key storage area 1 and changing it to another key stored in the key storage area 2 when the key needs to be changed. Time management means for determining whether or not it is time to change the key from the time when the key was last changed and the current time stored in the change time storage area 3, and 7 is an encryption for executing data encryption. Means, 8 is a current time acquisition means for acquiring the current time used by the time management means 6, 9 is a random number generation means for generating a random number when the key used by the key management means 5 is changed at random, and 10 is key management. Is a control means for controlling the execution of.

FIG. 2 is a circuit block diagram of the key management apparatus according to the embodiment of the present invention, showing a hardware configuration.

In FIG. 2, reference numeral 21 denotes a central processing unit (hereinafter abbreviated as CPU) for executing a program, 22
Is a random access memory (hereinafter abbreviated as RAM) for temporarily recording data, and 23 is a read only memory (hereinafter, RO) for storing a program.
M is abbreviated as M), 25 is a reading device for reading data from the recording medium 24, 26 is a secondary storage device for recording data such as an optical disk, and 27 is an internal data bus.

The correspondence between the functional means shown in FIG. 1 and the hardware shown in FIG. 2 will be described.

As shown in FIGS. 1 and 2, the used key storage area 1, the key storage area 2 and the key change time storage area 3 are R
It is realized by the AM 22 or the secondary storage device 26. In the communication unit 4, the key management unit 5, the time management unit 6, the encryption unit 7, the current time acquisition unit 8, the random number generation unit 9, and the control unit 10, the CPU 21 controls the ROM 23 and the RAM 2.
It is realized by executing the control program stored in the ROM 23 while exchanging data with the computer 2.

In the present embodiment, the CPU 21 uses the R
Although the control program stored in the OM 23 is executed, the recording medium 24 recording the control program
Alternatively, the control program may be read from the device via the reading device 25, expanded on the RAM 22 or the secondary storage device 26, and the expanded control program may be executed by the CPU 21. With such a configuration, the present invention can be easily realized by a general-purpose computer or the like.

In the following embodiments, the case of using the common key cryptosystem for encrypted communication will be described.
The present invention is applicable not only to encrypted communication but also to the case of using other common key cryptosystems such as authentication.

It is assumed that the transmitting side and the receiving side share a plurality of keys, and that the same index number specifies the same key on both sides.

The operation of changing the encryption key when performing encryption in the data transmitting device will be described with reference to the flowcharts of FIGS. 3 and 4.

In FIG. 3, first, key selection is performed to select which key to use (step 11). The key selection will be described in detail with reference to the flowchart of FIG.

In FIG. 4, the time management means 6 acquires from the key change time storage area 3 the time when the currently used common key is changed (step 21). Further, the time management means 6 requests the current time acquisition means 8 via the control means 10 to acquire the current time. The current time acquired by the current time acquisition means 8 is passed to the time management means 6 via the control means (step 22). In step 23, the time management means 6 calculates the usage time of the key used at the time of encryption by also referring to the key modification time acquired from the key modification time storage area 3. If the time obtained as a result does not exceed a certain value, the time management means 6 notifies the key management means 5 to that effect, and the key management means 5
The key selection processing ends without changing the key in use.

As a result of the calculation, if the value exceeds a certain value, the process proceeds to step 24, and the key changing process is executed. The key to change the key after a certain period of time is based on the idea that if you keep using the same key for a long time, the risk that a third party will understand the key you are using increases. This is because it is difficult to understand the key by changing the.

Next, in step 24, the key number to be used by the key management means 5 is updated, and in step 25, the key management means 5 acquires the changed key itself obtained from the key storage area 2, or The index number corresponding to the key is stored in the used key storage area 1. As a method of updating the key, a method of increasing the index number value of the currently used key by 1, a method of generating a random number and changing to a key having an index number corresponding to the generated random number, and the like can be considered.

After that, the key management means 5 controls the control means 1
0 to request the time management means 6 to store the current time acquired in step 22, and the time management means 6 stores the current time in the key change time storage area 3 (step 26), The key selection process ends. In addition, step 2
The key management step is composed of the procedures 1 to 24. Above, the explanation of FIG. 4 is completed and it returns to FIG.

In FIG. 3, when the key selection in step 11 is completed, the key number obtained by the key selection is used as the communication means 4
Transmits the key number to be used to the communication partner via the network (step 12). This is for designating which of the keys to use, even though the communication partner stores a plurality of keys. It should be noted that there is no security problem because the index is not the key itself but the index number indicating the key.

After transmitting the key number, the transmitting side waits for the communication means 4 in its own device to receive the response (step 13).
When the response is received, the process proceeds to step 14 and the control means 10
Check whether is a normal response. If it is a normal response, the process proceeds to step 15. If it is an abnormal response, the encrypted communication is stopped.

In step 15, the data to be transmitted with confidentiality is encrypted by the encryption means 7 using the key indicated by the key management means 5, and in step 16, the communication means 4 communicates the encrypted data. Send to the other party (reception side) and complete encrypted communication.

(Second Embodiment) A second embodiment will be described with reference to FIGS. 3 and 5. However, the difference from the first embodiment is only the key selection in step 11 in FIG. 3, so only this step will be described using FIG.

In step 31 of FIG. 5, the key management means 5
Requests the random number generation means 9 to generate a random number.
In step 32, the key management means 5 determines whether or not the key is changed based on the random number generated in step 31, and if the key is changed, the process proceeds to step 33. If the key is not changed, the key change process is ended. To do. As a method of determining whether or not the key is changed based on the generated random number, a key change may be performed if the generated random number is an odd number, and a change may not be performed if the generated random number is an even number.

At step 33, the key number to be used by the key management means 5 is updated, and at step 34, the key management means 5 acquires the changed key itself obtained from the key storage area 2,
Alternatively, the index number corresponding to the key is stored in the used key storage area 1, and the key selection process ends. As a key updating method, as in the embodiment, a method of incrementing the value of the index number of the currently used key by 1 or generating a random number and changing to a key having an index number corresponding to the generated random number Methods etc. are considered. In addition, step 3
The key changing step is constituted by the procedure of 1 to 33.

After that, the processes from step 12 onward in FIG. 3 are performed as in the case of the first embodiment.

[0051]

As described above, according to the present invention, a key storage area for storing a plurality of encryption keys and a used key storage area for storing the currently used key itself or an index number corresponding to the key. And communication means for communicating with the outside via a network such as the Internet, key management means for managing the key used during encryption and changing the key in use when the key needs to be changed, and various data. By adopting a configuration having a control means for controlling the flow of, the key to be used is switched when necessary when using the common key cryptosystem, so it is difficult for an unauthorized person to leak the key. The advantageous effect that the strength of the cryptosystem can be improved is obtained.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a key management device according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram of a key management device according to an embodiment of the present invention.

FIG. 3 is an operation flowchart of the key management device according to the embodiment of the present invention.

FIG. 4 is a key selection operation flowchart of the key management device according to the embodiment of the present invention.

FIG. 5 is a key selection operation flowchart of the key management device according to the embodiment of the present invention.

FIG. 6 is a conceptual diagram of partner authentication using common key cryptography.

[Explanation of symbols]

1 Key storage area 2 key storage area 3 Key change time storage area 4 Communication means 5 Key management means 6 hour management means 7 encryption means 8 Current time acquisition means 9 Random number generation means 10 Control means 21 CPU 22 RAM 23 ROM 24 recording media 25 reader 26 Secondary Storage Device 27 Internal data bus

Claims (12)

[Claims] 1. A key storage area for storing a plurality of encryption keys, a used key storage area for storing a currently used key itself or an index number corresponding to the key, and a network such as the Internet. Communication means for executing communication with the outside, key management means for managing the key used at the time of encryption and changing the key in use when it is necessary to change the key, and control for controlling various data flows A key management device comprising: 2. A key change time storage area for storing the key change time, a current time acquisition means for acquiring the current time, a last update time of the key stored in the key change time storage area, and a current time acquisition. The key management device according to claim 1, further comprising: a key management unit that refers to the current time acquired by the unit, and changes the key when a predetermined time has elapsed since the last key change. 3. A random number generating means for generating a random number, and whether or not a key is changed is determined based on the random number generated by the random number generating means, and the key or an index number corresponding to the key is stored in a used key storage area. The key management device according to claim 1 or 2, further comprising: 4. A key storage area for storing a plurality of encryption keys,
If it is necessary to manage the key used at the time of encryption and change the key to a key management device having a key storage area that stores a key itself currently used or an index number corresponding to the key A key selection step including a key selection step of changing the key in use and a key storage step of storing the changed key itself or an index number corresponding to the key, and communication with the outside via a network such as the Internet And a communication step for executing the key management method. 5. The key management device is provided with a key change time storage area for storing the key change time, and the key selecting step is the last update time of the key stored in the key change time storage area. A key change time acquisition step for acquiring the current time, a current time acquisition step for acquiring the current time, and a key change time acquired in the key change time acquisition step, and a current time acquired in the current time acquisition step, The key management method according to claim 4, further comprising a key management step of changing the key when a predetermined time has elapsed since the last key change. 6. The key selecting step includes: a random number generating step of generating a random number; and a key changing step of determining whether a key is changed based on the random number generated in the random number generating step. The key management method according to claim 4 or 5. 7. A key storage area for storing a plurality of encryption keys,
If it is necessary to manage the key used at the time of encryption and change the key to a key management device having a key storage area that stores a key itself currently used or an index number corresponding to the key A key selection step including a key selection step of changing the key in use and a key storage step of storing the changed key itself or an index number corresponding to the key, and communication with the outside via a network such as the Internet A key management program that causes a computer to execute a communication step for executing. 8. The key management device is provided with a key change time storage area for storing the key change time, and the key selecting step is the last update time of the key stored in the key change time storage area. A key change time acquisition step for acquiring the current time, a current time acquisition step for acquiring the current time, and a key change time acquired in the key change time acquisition step, and a current time acquired in the current time acquisition step, 8. The key management program according to claim 7, further comprising a key management step of changing the key when a predetermined time has passed since the last key change. 9. The key selecting step includes: a random number generating step of generating a random number; and a key changing step of determining whether a key is changed based on the random number generated in the random number generating step. The key management program according to claim 7. 10. A key management device having a key storage area for storing a plurality of encryption keys and a currently used key itself or a used key storage area for storing an index number corresponding to the key. A key selecting step of managing the key used during encryption and changing the key in use when the key needs to be changed, and a key storing step of storing the changed key itself or an index number corresponding to the key A computer-readable recording medium having recorded therein a key management program for causing a computer to execute a key selecting step including: and a communication step for performing communication with the outside via a network such as the Internet. 11. The key management device is provided with a key change time storage area for storing the key change time, and the key selecting step is the last update time of the key stored in the key change time storage area. A key change time acquisition step for acquiring the current time, a current time acquisition step for acquiring the current time, and a key change time acquired in the key change time acquisition step, and a current time acquired in the current time acquisition step, A computer-readable recording medium having a key management program according to claim 10, further comprising a key management step of changing the key when a predetermined time has elapsed since the last key change. 12. The key selecting step includes: a random number generating step of generating a random number; and a key changing step of determining whether or not a key is changed based on the random number generated in the random number generating step. A computer-readable recording medium in which the key management program described in [1] is recorded.