JPH06259012A - Enciphering method by hierarchic key control and information communication system - Google Patents

Abstract

PURPOSE:To improve the safety of a file that plural users shares in environment where users are hierarchically sectioned according to kinds of information which can be accessed and to correctly decode a ciphertext file, controlled by a user belonging to one layer, by a user belonging to a layer above the layer. CONSTITUTION:A terminal 100 reads a key generation right list 131 and a ciphertext 132, making a group with a file name 130 that the user inputs, out of a storage device 120 and sends only the key generation right list 131 to an IC card 110. When the received key generation right list 131 and the card identification number 133 of an IC card 110 satisfy specific relation, the IC card 110 generates a data key 135 on the basis of a master key selected from among the key generation right list 131 and its card master key list 134 and sends the data key to the terminal 100. The terminal 100 decodes the ciphertext 132 with the received data key 135 to generate a plaintext 136.

Description

Detailed Description of the Invention

[0001]

The present invention relates to information shared by a plurality of users in an environment where users can be hierarchically divided according to the type and importance of accessible information, such as a company organization. The present invention relates to an encryption method that can be properly encrypted and an information communication system to which such an encryption method is applied. More specifically, encrypted information managed by a user who belongs to a certain layer is stored in the upper layer. The present invention relates to an encryption method and an information communication system that enable a user to which the user belongs to correctly decrypt.

[0002]

2. Description of the Related Art With the development of information and communication equipment, a local area network (LAN) using terminals such as workstations and personal computers has come into widespread use. Along with this, various kinds of information have been digitized and sent.

In a LAN, information is broadcast on the line. That is, the information transmission source attaches the address of the other party to the information to be transmitted and transmits it to the line, and all terminals on the line receive this. The terminal side receiving the information refers to the address and checks whether or not the information is transmitted to itself. Therefore, the information sent by a certain terminal in a broadcast manner can be basically received by any terminal. Therefore, when sending highly confidential information,
Information is protected using security technologies such as encryption and access control.

On the other hand, under such an environment, file sharing is performed in order for a plurality of users to work together. The file shared by a plurality of users has an influence on a large number of users at a time when the correct content is leaked to a third party as compared with the file for each individual. Therefore, it is necessary to properly protect the information stored as a file in this manner by using security techniques such as encryption and access control, like the information sent on the communication line.

When encrypting the information sent on the communication line or encrypting the information stored as a file, it is necessary to share the encryption key between the correspondents or the users who share the file. is there.

However, when the information stored as a file is encrypted, the following problems occur.

[0007] When encrypting the information sent over the communication line, the encryption key can be made disposable for each session, but when encrypting the file information,
You don't know when to decrypt the ciphertext, so you have to save the ciphertext along with the ciphertext.

A method for properly encrypting a file is disclosed, for example, in "Cryptography and Information Security (edited by Shigeo Tsujii, Masao Kasahara; published by Shokoido)".

In the above disclosed example, the file is first encrypted with a randomly generated random number to generate a ciphertext file. Further, the random number is also encrypted with a secret number unique to the system called a master key to generate a ciphertext key (encrypted encryption key). Then, this ciphertext key is stored together with the ciphertext file. When reading a file, the ciphertext key is first decrypted with the master key, and then the ciphertext file is decrypted.

At this time, whether or not the user has the right to decrypt the ciphertext file and read the correct contents can be checked only by separately controlling access to the file (method of checking whether or not the person has the right to access the file). Is going.

[0011]

By the way, for example, in a company organization as shown in FIG. 21, users can be hierarchically classified according to the type and importance of accessible information. In such an environment, the file created by the subordinate can be read by the superior, but there is a demand that the file created by the superior cannot be read by the subordinate.

[0012] However, in the above-mentioned conventional technique, since it is checked only by the access control whether or not the right to read the correct contents is obtained, the boss must know the master keys of all subordinates belonging to his or her subordinates. . Otherwise, the subordinate cannot decrypt the encrypted file. However, managing the master keys of all the subordinates imposes a heavy burden on the user. Also, for terminals that do not have access control functions, such as personal computers,
There is a problem that it cannot be applied.

Therefore, an object of the present invention is to provide a cryptographic method and apparatus capable of properly encrypting a file shared by a plurality of users without increasing the burden on the users to enhance security. To do.

Another object of the present invention is to provide a ciphertext file managed by a user belonging to a certain hierarchy,
An object of the present invention is to provide an encryption method and device that allows a user belonging to the upper layer to correctly decrypt it.

[0015]

In order to achieve the above object, in the first aspect, the present invention first generates an encryption key from the identification number of a storage medium (for example, an IC card) distributed to each user. An encryption method is provided, which is characterized by checking whether or not there is a right to do so and generating an encryption key according to the result.

[0016] In a second aspect, the present invention not only checks whether a user who is permitted by the file creator in advance when decrypting a ciphertext file, but also determines whether the user belongs to an upper layer of the user. An encryption method is provided which is characterized by also performing the check.

According to a third aspect, the present invention prepares a master key used for encryption key generation for each user layer, and distributes to each user the master key of the layer to which the user belongs and the master key of the lower layer. An encryption method is provided.

[0018]

With the encryption method according to the first aspect, a file shared by a plurality of users can be properly encrypted without imposing too much burden on the users.

In the encryption method according to the second aspect, when determining whether or not there is a right to generate an encryption key, it is also checked whether the user belongs to a higher hierarchy than the user permitted by the file creator. I'm doing so
A ciphertext file managed by a user belonging to a certain layer can be correctly decrypted by a user belonging to the upper layer.

In the encryption method according to the third aspect described above, the user cannot obtain the master key of the hierarchy higher than the hierarchy to which the user belongs, so that the ciphertext file managed by the user belonging to a certain hierarchy is A user belonging to the lower hierarchy cannot correctly decrypt.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same numbers represent similar parts and elements. This does not limit the present invention.

(Example 1)

FIG. 1 is a first embodiment of the present invention and is a block diagram showing a procedure for decrypting ciphertext (file information) in a system to which the encryption method according to the present invention is applied. FIG. 2 is a block diagram showing the system configuration of the system of this embodiment.

First, the system configuration of this embodiment will be described with reference to FIG.

In FIG. 2, reference numerals 100 and 101 denote terminals such as workstations and personal computers. The user performs various tasks using these terminals. A storage device 120 is connected to the terminals 100 and 101 by the communication network 210. The user can store files created using the application program in the storage device 120. Further, the information in the storage device 120 can be read.

Reference numerals 110 and 111 denote IC cards, which are distributed to each user in advance, one by one. The user inserts his or her IC card into the reader / writer 20.
Plug in 0, 201 and work. IC card 1
The terminals 10 and 111 exchange data with the terminals 100 and 101 via the reader / writers 200 and 201.

FIG. 3 is an internal block diagram of the terminal 100.
Other terminals such as the terminal 101 have the same configuration. As shown in the figure, the terminal 100 has a communication network interface 301.
, Reader / writer interface 302, CPU (central processing unit) 303, display device 304, and input device 3
05 and a memory 306. They are connected to each other by a bus 300.

The communication network interface 301 is the communication network 2
This is an interface for exchanging data with the storage device 120 via the storage device 10. The reader / writer interface 302 is connected to the reader / writer 2 via the cable 310.
This is an interface for exchanging data with 00. The CPU 303 has an arithmetic function and controls the operation of the entire terminal. The display device 304 is a display or the like for displaying a message to the user.
The input device 305 is a keyboard, a mouse or the like for the user to input data. The memory 306 includes a communication program 307, an application program 308,
A security program 309 and the like are stored.

The communication program 307 stored in the memory 306 is a program for controlling the data exchange with the storage device 120 or the reader / writer 200. Application program 308
Is a program that supports and controls a user when creating a new file or reading or writing an existing file. In addition, the security program 309
Is a program that performs various processes related to file encryption and decryption.

FIG. 4 is an internal block diagram of the IC card 110. The configurations of other IC cards such as the IC card 111 are similar. As shown in the figure, the IC card 110 has a C
PU401, reader / writer interface 402,
It has a memory 403. They are connected to each other by a bus 400.

The CPU 401 has an arithmetic function and controls the entire processing in the IC card. The reader / writer interface 402 is an interface for exchanging data with the reader / writer 200. A communication program 404, a security program 405, a master key list 406, a card identification number 407, etc. are stored in the memory 403.

The communication program stored in the memory 403 is a program for controlling the data exchange with the reader / writer 200. The security program 405 is a program that performs various processes when generating an encryption key based on the information sent from the terminal 100 via the reader / writer 200.

The master key list 406 shows the IC card 1 among the master keys which are secret numerical values common to each user hierarchy.
It is a numerical sequence composed of the master keys of the hierarchy to which the ten owners belong and the lower hierarchy.

For example, assume that the organization to which the system of this embodiment is applied has a hierarchical structure as shown in FIG. A,
B, C, ... Show each person constituting the organization, and the person at the top is the boss. For example, J-P's boss is F, and E-
G's boss is B. In the case of such an organization, the constituent elements of the master key list of the IC card owned by B belonging to the second layer are KM2, KM3, and KM4. In other words, the IC card of B has the master key KM of its own layer.
In addition to 2, master keys KM3 and KM4 in the lower hierarchy are also stored. The constituent element of the master key list of the M IC card belonging to the fourth layer is only KM4.

Referring again to FIG. 4, the card identification number 40
The numeral 7 is a numerical value specific to the IC card 110. When all users are structured as shown in FIG. 5, the card identification number 407 indicates at which node the owner of the IC card 110 is located.

The card identification numbers of all IC cards are stored in the storage device 120 in the form of an identification number table 600 as shown in FIG. 6, for example. In the identification number table 600 of FIG. 6, “name” indicates the names of all those who own IC cards belonging to this organization, and “post” indicates the post of that person. The “personal identification number” is an identification number unique to the individual (such as a staff number). The "card identification number" is the value of the card identification number 407 of the above IC card.

As described above, the position (so to speak) of the owner of the IC card within the organization can be known by the card identification number. For example, since the organization of FIG. 5 has four layers as a whole, the card identification number is formed by arranging four numerical values as shown in FIG.

The card identification number is a position where "0" appears when referring to the card from the left side, and the layer to which the card belongs can be known. For example, the card identification number of the IC card owned by A is (1, 0, 0, 0), but the first numerical value when viewed from the left is "1" other than "0", and the next second Since the numerical value of is “0”, it can be seen that A belongs to the first layer. The card identification number of the IC card owned by G is (1, 1, 3, 0), but the first numerical value is "1" other than "0", and the second numerical value is "1". "1" other than "0", "3" when the next third numerical value is other than "0",
Since "0" appears at the next fourth position, it can be seen that G belongs to the third layer.

Furthermore, the position within the tissue can be known by the numerical values before the appearance of "0". For example, IC owned by C
The card identification number of the card is (1, 2, 0, 0), but the owner of this card has the first number "1".
The first person in the hierarchy (card identification number (1, 0, 0,
It turns out that he is a subordinate of (0). Also, with the second numerical value "2" before the appearance of "0", the owner of this card is the second of its subordinates (ie,
It can be seen that it is C) of FIG. Similarly, for example,
With the card identification number of L (1, 1, 2, 3), this I
If the owner of the C card is the card identification number (1, 1, 2,
It is understood that he is a subordinate of the person 0) and is the third subordinate of the subordinates.

Next, referring to FIG. 1, the procedure for decrypting the ciphertext (ciphertext file) already stored in the storage device 120 in this embodiment will be briefly described.

First, the user inputs the file name 130 of the file to be read. The terminal 100 sends the file name 130 input by the user to the storage device 120. The storage device 120 stores the key generation right list 131 and the ciphertext 132 paired with the file name 130 in the terminal 10
Send to 0. The terminal 100 selects the key generation right list 13 out of the read key generation right list 131 and ciphertext 132.
Only 1 is sent to the IC card 110.

The key generation right list is a list of card identification numbers indicating persons who have the right to read and decrypt the file. In this embodiment, the data has a format in which card identification numbers indicating the persons who have the access right to the file are concatenated, but it may be expressed in another format. Any data can be used as long as it can identify the card identification number indicating the person who has the access right. The key generation right list is generated when the person who created the file writes the file in the storage device 120, and is written in the storage device 120. The person who created the file determines who is given access.

The IC card 110 checks the key generation right 141 whether the received key generation right list 131 and the received card identification number 133 satisfy a specific relationship. Checking a specific relationship means own card identification number 13
3 is specified in the key generation right list 131,
Alternatively, the own card identification number 133 is the key generation right list 13
It is a check regarding whether or not the boss designated as 1 is shown. In other words, it is checked whether the person has the access right specified in the key generation right list 131 or the boss thereof.

The IC card 110 has a key generation right check 1
In 41, a master key is selected from the own card master key list 134 using the master key selection algorithm 142 only when the key generation right list 131 and the own card identification number 133 satisfy a specific relationship. The master key selection algorithm 142 checks the hierarchy of the person who is designated as having the access right in the key generation right list 131, and selects the master key of the lowest hierarchy from the master key list 134. This is because the IC card of the person in the upper layer stores the master key of the lower layer, while the IC card of the person in the lower layer does not store the master key of the upper layer. That is, the master key is adjusted to the lowest hierarchy among those who have access rights.

Next, the IC card 110 generates the data key 135 based on the key generation right list 131 and the selected master key, and sends it to the terminal 100.

The terminal 100 receives the received data key 135.
By using the cipher algorithm 140 and the ciphertext 132.
Is decrypted and a plaintext 136 is generated. As described above, the plaintext 136 can be obtained.

Next, referring to FIG. 7 to FIG. 10, the user's operation, the terminal 100 and the IC card 1 in this embodiment are performed.
The internal processing of 10 will be described in detail.

FIG. 7 is a flow chart showing a processing procedure when a plaintext file is encrypted and written in the storage device 120.

This processing is performed by the user in his own IC card 11
It is started by inserting 0 into the reader / writer 200 and using the input device 305 to write a plaintext file created by the application program 308 in the storage device 120 (step 700).

The terminal 100 first reads the identification number table 600 (FIG. 6) in the storage device 120 and displays it on the display device 304 (step 701). The user
By referring to the displayed identification number table 600, the sharing partner of the created plaintext file is designated using the input device 305. The terminal 100 generates a key generation right list including the card identification numbers of all the designated users (step 702). Then, the key generation right list is sent to the IC card 110 (step 703).

The IC card 110 generates a data key based on the key generation right list sent from the terminal 100,
It is sent back to the terminal 100 (step 704). The processing of the IC card 110 will be described later with reference to FIG.

The terminal 100 uses the data key sent from the IC card 110 to encrypt the plaintext file (step 705). Then, the generated ciphertext file, the file name, and the key generation right list are paired and written in the storage device 120 (step 706).

Finally, the user removes the IC card 110 from the reader / writer 200, and all the processing is completed (step 707).

FIG. 8 is a flow chart showing the key generation processing (step 704) inside the IC card 110 in FIG. 7 in more detail. In this process, the IC card 110 is used by the terminal 10
It starts by receiving the key generation right list from 0 (step 800).

First, the IC card 110 checks whether or not the constituent elements of the received key generation right list include its own card identification number (step 801). If it is included, the process proceeds to step 802 to continue the processing. If not included, the process ends (step 80).
4).

When the component of the received key generation right list includes the own card identification number, the IC card 110
Refers to the key generation right list, and selects the master key assigned to the lowest user hierarchy among the constituent elements from the master key list (step 80).
2). Then, a data key is generated from the selected master key and the key generation right list, and it is sent back to the terminal 100 (step 803). Then, all the processes are finished (step 804).

FIG. 9 is a flowchart showing the processing procedure for reading the ciphertext file stored in the storage device 200 and decrypting it.

This process is started by the user inserting the IC card 110 into the reader / writer 200 and reading the ciphertext file stored in the storage device 120 (step 900).

The terminal 100 first reads the file name of each ciphertext file stored in the storage device 120,
The file list is displayed on the display device 304 (step 901).

The user refers to the displayed list of file names and specifies the file name to be read using the input device 305. The terminal 100 reads, from the storage device 120, the ciphertext file and the key generation right list that are stored in combination with the designated file name (step 9).
02). Then, only the key generation right list is sent to the IC card 11
0 (step 903).

The IC card 110 generates a data key based on the key generation right list sent from the terminal 100 and sends it to the terminal 100 (step 904). The processing of the IC card 110 will be described later with reference to FIG.

The terminal 100 decrypts the ciphertext file using the data key sent from the IC card 110 (step 905). Finally, the user sets the reader / writer 2
By taking out the IC card 110 from 00, all processing is completed (step 906).

FIG. 10 is a flow chart showing the key generation processing (step 904) inside the IC card in FIG. 9 in more detail. Since the procedure of FIG. 10 is basically the same as that of FIG. 8, steps performing the same processing are denoted by the same reference numerals.

However, in FIG. 10, the data key is generated even when the own card identification number satisfies a certain relation with the card identification number included in the key generation right list received from the terminal 100. The difference is that they are forgiving (steps 1000 and 1001). The certain relationship in this case is that the owner of the IC card is the boss of the user whose card identification number is included in the key generation right list.

For example, when a card identification number is assigned as shown in FIG. 6, it is determined whether the card identification number in the IC card and the card identification number included in the key generation right list satisfy this relationship. , Is inspected as follows. That is, the exclusive OR of the card identification number in the IC card and all the card identification numbers included in the key generation right list is calculated, and the numerical values up to the layer to which the owner of the IC card belongs are inspected. They are all 0
If so, it can be determined that the relationship is satisfied.

This is to set a card identification number of a subordinate of a certain person (boss) to "1", "2" ... at the position of "0" which appears first from the left with the card identification number of the boss. This is because it is configured with. For example, in FIG.
The exclusive OR of the B card identification number (1, 1, 0, 0) of G and the card identification number of G (1, 1, 3, 0) is (0,
0,0,0), it is clear that B and C have a relationship with their superior and subordinate.

In the above-described embodiment, the user designated by the file creator and the user having a specific relationship with those users (for example, the boss in the above-described example) connect their own IC card to the terminal. A correct data key is generated inside the IC card only when it is inserted into the reader / writer. Therefore, a third party who does not have an IC card or a user who does not have the right to read the file cannot know the correct content, and the safety of the shared file is increased.

Further, since the data key is not shared in advance for each other who will share the file, the data key is generated each time inside the IC card from the key generation right list or the master key list. It is possible to reduce the burden on the user who has a lot of people who share the file, and to safely share the file with any person.

(Example 2)

Next, a second embodiment of the present invention will be described.
The second embodiment is basically the same as the above-mentioned first embodiment. The system configuration of the system, the internal configuration of the terminal, and the internal configuration of the IC card are the same as those in FIGS. 2, 3 and 4 of the above-described first embodiment, and the decryption procedure of the ciphertext (file information) is also performed. It is similar to FIG. Further, the structure of the identification number table is the same as that in FIG.

In the first embodiment, the plaintext file is encrypted by the procedure of FIG. 7 and written in the storage device 120, but in the second embodiment, the procedure of FIG. 11 is used.

With reference to FIG. 11, a processing procedure for encrypting a plaintext file and writing it in the storage device 120 in this embodiment will be described. 11, the same processing steps as those in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted. Figure 11
Then, steps 1100 and 1101 are added.

That is, in step 1100, the card identification number of the user designated using the input device 305,
A card identification number satisfying a certain specific relationship (for example, a card identification number of a boss of a designated user) is set to the terminal 100
Generate in advance. And step 110
At 1, the card identification number is added to the key generation right list. The key generation right list of the added result is displayed in step 703.
Then, it is transmitted to the IC card 110.

Further, in this embodiment, the storage device 120
The processing procedure for reading the ciphertext file stored in and decrypting it is the same as in FIG. Also, IC
The key generation process inside the card is the same as in FIG. 8 regardless of whether the file is written or read.

In the first embodiment, a specific relationship is checked when reading a file so that, for example, the boss can also read the file. On the other hand, in the present embodiment, when writing a file in advance, a card identification number satisfying a specific relationship, for example, a boss card identification number,
It is generated and added to the key generation right list. Therefore, in addition to obtaining the same effect as the first embodiment, it is possible to reduce the processing in the IC card, which is generally inferior to the terminal in performance, and to achieve higher speed.

(Example 3)

Next, a third embodiment of the present invention will be described.
The third embodiment is basically the same as the above-mentioned first embodiment. The system configuration of the system and the internal configuration of the terminal are the same as those in FIGS. 2 and 3 of the first embodiment described above. The structure of the identification number table is similar to that of FIG.

FIG. 12 is a block diagram showing the outline of the procedure for decrypting ciphertext (file information) in this embodiment. In FIG. 12, the same processes or information as those in FIG. 12 is different from FIG. 1 in blocks 1200 and 1210.

That is, in this embodiment, the IC card 11
0, the required master key is not selected from the master key list, but the required master key for hierarchy is generated from the master key for hierarchy 1200 using the master key generation algorithm 1210. Hierarchical master key 1
200 is a master key of the hierarchy to which the owner of the IC card belongs. For example, in the organization of FIG. 5, the IC card owned by A stores the master key KM1 of the first hierarchy as a hierarchy-based master key, and the IC card owned by B is the master key KM2 of the second hierarchy as a hierarchy-based master key. I remember.

FIG. 13 is a diagram showing that hierarchy-specific master keys are generated in advance in association with each other, and a lower hierarchy master key can be generated from an upper hierarchy master key. That is, the i + 1st layer master key 1301 can be generated from the ith layer master key 1300 using the one-way function 1310. Since it is a one-way function, it is not possible to generate the master key of the upper layer from the master key of the lower layer.

FIG. 14 is a block diagram showing the internal structure of the IC card, which is basically the same as FIG. However, the memory 403 stores only one hierarchical master key 1400, not the master key list. In addition,
The one-way function 1310 is the security program 405.
Is equipped with.

FIG. 15 is a flow chart showing a key generation process inside the IC card when writing and reading a file. This is basically the same as in FIG. However, the required hierarchy master key is generated from the hierarchy master key of the own card (step 1500), and the data key is generated from the generated hierarchy master key and the key generation right list (step 1501). The points are different.

The processing procedures for writing and reading a file in this embodiment are the same as those in FIGS. 11 and 9, respectively.

According to this embodiment, in addition to the same effects as those of the first and second embodiments, the amount of information that must be stored in the IC card can be reduced, and users to be classified can be classified. This is effective when there are many layers.

(Example 4)

Next, a fourth embodiment of the present invention will be described.
The fourth embodiment is basically the same as the above-mentioned third embodiment. The system configuration of the system and the internal configuration of the terminal are the same as those in FIGS. 2 and 3 of the first embodiment described above. The structure of the identification number table is similar to that of FIG.

FIG. 16 is a block diagram showing the outline of the procedure for decrypting ciphertext (file information) in this embodiment. In FIG. 16, the same processes or information as those in FIG. 12 are given the same numbers and their explanations are omitted. 12 is different from FIG. 1 in that blocks 1600, 1610, 1601, 1
611.

That is, in this embodiment, before the key generation right check 141 is performed, it is confirmed whether the owner of the IC card is surely located at the node (post) described in the identification number table. The difference is that the check 1611 is performed.

FIG. 17 is a block diagram showing the internal structure of the IC card, which is basically the same as FIG.
However, in addition to the above, the memory 403 also stores a personal identification number 1700 which is a numerical value different for each user.

FIG. 18 is a flow chart showing a processing procedure when a plaintext file is encrypted and written in the storage device 120 in this embodiment. This is basically the same as in FIG. However, step 704 of FIG.
It has been replaced by 800, 1801, 1802.

In FIG. 18, when the key generation key list is sent to the IC card in step 703, in step 1800 I
The C card performs data key generation processing 1. This is the process of step 2000 in FIG. 20 described later, which is a process in which the IC card returns its own card identification number to the terminal.

In step 1801, the terminal refers to the identification number table 1600, searches for the personal identification number corresponding to the card identification number received from the IC card, and returns the obtained personal identification number to the IC card 110. . In step 1802, the IC card performs the data key generation process 2. This is a process after step 2001 of FIG. 20 which will be described later, and is a process of checking a personal identification number and generating a data key.

FIG. 19 shows the storage device 2 in this embodiment.
10 is a flow chart showing a processing procedure when a ciphertext file stored in 00 is read and the ciphertext file is decrypted. This is basically the same as in FIG. However, as in FIG.
Step 904 in FIG. 9 corresponds to steps 1800, 1801,
It has been replaced by 1802. That is, by referring to the identification number table 1600, a personal identification number corresponding to the card identification number received from the IC card is searched, the obtained personal identification number is returned to the IC card, and the personal identification number is checked. The point to do is different.

FIG. 20 is a flow chart showing a key generation process inside the IC card when writing and reading a file. This is basically the same as in FIG. However, the difference is that steps 2000 and 2001 are added.

That is, when the key generation right list is received from the terminal, first, the card identification number is sent to the terminal 100 (step 2000). This step 2000 is shown in FIG.
This corresponds to steps 1800 of 8 and 19. 18 and 19
As described above, the terminal sends the personal identification number corresponding to the card identification number received from the IC card to the IC card. The IC card checks whether the returned personal identification number and the personal identification number in its own card match (step 2001).

According to this embodiment, in addition to the same effects as those of the first to third embodiments, there is a change in the node (post) where the user is located (at this time, according to the change). The identification number table in the storage device has been rewritten), and it is possible to prevent the file from being decrypted by the previous user, which can increase the security and expandability.

[0097]

As described above, according to the encryption method of the present invention, ICs owned by users who share files
Since the encryption key is generated by using the identification number of the storage medium such as a card, it is possible to properly encrypt the file shared by a plurality of users and enhance the security of information. Moreover, since it is not necessary to have all the master keys of the users in the lower hierarchy than himself, the burden on the user is reduced.

Further, since the identification number of the storage medium such as the IC card is set according to the user hierarchy, the encrypted information managed by the user belonging to a certain hierarchy is stored in the upper hierarchy. A user belonging to can be correctly decrypted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a system configuration diagram of the first embodiment.

FIG. 3 is an internal configuration diagram of a terminal in the first embodiment.

FIG. 4 is an internal configuration diagram of an IC card according to the first embodiment.

FIG. 5 is a configuration diagram of a user and a master key in the first embodiment.

FIG. 6 is a configuration diagram of an identification number table in the first embodiment.

FIG. 7 is a flowchart showing a processing procedure for encrypting a plaintext file in the first embodiment.

FIG. 8 is a flow chart showing processing inside the IC card when a plaintext file is encrypted in the first embodiment.

FIG. 9 is a flowchart showing a processing procedure for decrypting a ciphertext file in the first embodiment.

FIG. 10 is a flowchart showing the processing inside the IC card when a ciphertext file is decrypted in the first embodiment.

FIG. 11 is a flowchart showing a processing procedure when a plaintext file is encrypted in the second embodiment of the present invention.

FIG. 12 is a block diagram showing a third embodiment of the present invention.

FIG. 13 is a block diagram showing a method of generating a hierarchy-specific master key according to the third embodiment.

FIG. 14 is an internal configuration diagram of an IC card according to a third embodiment.

FIG. 15 is a flow chart showing processing inside the IC card in the third embodiment.

FIG. 16 is a block diagram showing a fourth embodiment of the present invention.

FIG. 17 is an internal configuration diagram of an IC card according to a fourth embodiment.

FIG. 18 is a flowchart showing a processing procedure for encrypting a plaintext file in the fourth embodiment.

FIG. 19 is a flowchart showing a processing procedure for decrypting a ciphertext file in the fourth embodiment.

FIG. 20 is a flowchart showing the processing inside the IC card in the fourth embodiment.

FIG. 21 is a diagram showing a configuration of users hierarchized by post.

[Explanation of symbols]

 100, 101 ... Terminal, 110, 111 ... IC card, 120 ... Storage device, 200, 201 ... Reader / writer, 210 ... Communication network.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Matsumoto 3-10-22 Sakae, Naka-ku, Nagoya-shi, Aichi Hiritsu Chubu Software Co., Ltd.

Claims (17)

[Claims] 1. In an information communication system comprising a plurality of terminals mutually connected by a communication network and a storage device accessible from the plurality of terminals, a file on the storage device is shared by a plurality of users. An encryption method for performing encryption, wherein the terminal is a storage medium provided with a calculation function in advance to a user, and a storage medium identification number unique to the storage medium and a secret called a plurality of master keys. A storage medium that stores a master key list composed of numerical values can be connected, and when writing a file from a certain terminal to the storage device, a key that is a list of storage medium identification numbers that represents the sharers of the file to be written Generating a generation right list and transmitting the key generation right list from a terminal to a storage medium connected to the terminal; And selecting a master key based on the received key generation right list, generating a data key based on the selected master key and the received key generation right list, and returning the data key to the terminal. , A plaintext file is encrypted using the data key to generate a ciphertext file, and the ciphertext file, the key generation right list, and the file name are written to the storage device. To read a file from the storage device according to, the step of reading the ciphertext file and the key generation right list from the storage device according to the specified file name, and connecting the read key generation right list to the terminal To the stored storage medium, and in the storage medium, whether the received key generation right list includes its own storage medium identification number, or Determines whether or not the storage medium identification number included in the key generation right list and the own storage medium identification number have a predetermined relationship, and by the checking step, self-stores in the received key generation right list. When the medium identification number is included or the storage medium identification number included in the key generation right list and the own storage medium identification number have a predetermined relationship, the master key is set based on the key generation right list. Select and generate a data key based on the selected master key and the received key generation right list,
An encryption method, comprising: returning to a terminal; and decrypting the ciphertext file using the data key in the terminal to generate a plaintext file. 2. In an information communication system comprising a plurality of terminals mutually connected by a communication network and a storage device accessible from the plurality of terminals, a file on the storage device is shared by a plurality of users. An encryption method for performing encryption, wherein the terminal is a storage medium provided with a computing function in advance to a user, and a storage medium identification number unique to the storage medium and a secret called a plurality of master keys. A storage medium that stores a master key list composed of numerical values can be connected, and when writing a file from a certain terminal to the storage device, a key is a list of storage medium identification numbers that represent the sharers of the file to be written. Generating a generation right list and transmitting the key generation right list from a terminal to a storage medium connected to the terminal; And selecting a master key based on the received key generation right list, generating a data key based on the selected master key and the received key generation right list, and returning the data key to the terminal. , A step of generating a ciphertext file by encrypting a plaintext file using the data key, and a step of writing the ciphertext file, the key generation right list, and the file name in the storage device. And the encryption method. 3. In an information communication system comprising a plurality of terminals mutually connected by a communication network and a storage device accessible from the plurality of terminals, a file on the storage device is shared by a plurality of users. An encryption method for reading and decrypting, wherein the terminal is a storage medium provided with a calculation function in advance to a user, and is called a storage medium identification number unique to the storage medium and a plurality of master keys. A storage medium storing a master key list composed of secret numbers can be connected, and in the storage device, a file name of a file shared by a plurality of users and a storage medium identification number indicating a sharer of the file are stored in advance. Based on the key generation right list and the master key selected by the key generation right list. A ciphertext file encrypted with the generated data key is stored, and when a file is read from the storage device by a certain terminal, the ciphertext file is stored as a ciphertext file from the storage device according to the specified file name. Reading the key generation right list; transmitting the read key generation right list to a storage medium connected to the terminal; and in the storage medium, the received key generation right list has its own storage medium identification number. A step of inspecting whether or not the storage medium identification number included in the key generation right list and the own storage medium identification number included in the key generation right list have a predetermined relationship; and the received key generation by the inspection step. The right list includes its own storage medium identification number or the key generation right list includes a storage medium identification number and its own storage medium identification number. When in, select the master key based on said key generation rights list, generates the data key based on the key generation permission list received the master key and said selected,
An encryption method, which comprises performing a step of returning to a terminal and a step of decrypting the ciphertext file using the data key in the terminal to generate a plaintext file. 4. The encryption method according to any one of claims 1 to 3, wherein the storage medium is an IC card. 5. The encryption method according to claim 1, wherein all users are hierarchically divided according to the type and importance of accessible information, and
The storage medium identification number is set so that the hierarchy of the user who owns the storage medium is known, and the predetermined relationship in the checking step is that the hierarchy indicated by the self storage medium identification number is in the key generation right list. An encryption method characterized in that it has a relationship of being an upper layer of a layer indicated by the included storage medium identification number. 6. The encryption method according to claim 1, wherein the storage medium identification number represents a relationship between a user of the storage medium and another user. 7. The encryption method according to claim 1, wherein the step of generating a data key and returning it to the terminal when writing a file to the storage device is the received key generation right list. An encryption method characterized in that the data key is generated and returned to the terminal only when the own storage medium identification number is included in. 8. The encryption method according to claim 5, wherein the master key list in the storage medium is a hierarchy to which a user who owns the storage medium belongs among the master keys whose secret numerical values are different for each user hierarchy. An encryption method comprising a master key of the above and a master key of a lower hierarchy thereof. 9. The encryption method according to claim 8, wherein when a data key is generated inside the storage medium when writing or reading a file to or from the storage device, the storage medium identification is included in the key generation right list. An encryption method characterized by selecting and using a master key of the lowest hierarchy among hierarchies to which a user including a number belongs. 10. In an information communication system comprising a plurality of terminals mutually connected by a communication network and a storage device accessible from the plurality of terminals, a file on the storage device is shared by a plurality of users. An encryption method for performing encryption, wherein the terminal is a storage medium provided with a computing function in advance to a user, and a storage medium identification number unique to the storage medium and a secret called a plurality of master keys. A storage medium that stores a master key list composed of numerical values can be connected, and when writing a file from a certain terminal to the storage device, a key is a list of storage medium identification numbers that represent the sharers of the file to be written. The key is generated by generating a generation right list and calculating a storage medium identification number having a predetermined relationship with the storage medium identification number of the key generation right list. Adding to the authorization list and transmitting the added key generation authority list from the terminal to a storage medium connected to the terminal, and selecting a master key in the storage medium based on the received key generation authority list Then, a step of generating a data key based on the selected master key and the received key generation right list and returning the data key to the terminal, and encrypting the plaintext file using the data key at the terminal, and encrypting the plaintext file. The step of generating a text file and the step of writing the ciphertext file, the key generation right list, and the file name into the storage device are performed, and the reading of the file from the storage device by a certain terminal is performed by the designated file. The step of reading the ciphertext file and the key generation right list from the storage device according to the name, and the read key generation right list to the terminal. To the subsequent storage medium, a step of checking whether the received key generation right list in the storage medium includes the own storage medium identification number, and a step of checking the received key generation right list , The master key is selected based on the key generation authority list, and the data key is generated based on the selected master key and the received key generation authority list. , A step of returning to the terminal, and a step of decrypting the ciphertext file using the data key in the terminal to generate a plaintext file. 11. The encryption method according to claim 2, wherein a key, which is a list of storage medium identification numbers representing sharers of a file to be written, when the key generation right list is generated when writing a file to the storage device. An encryption method, wherein a generation right list is generated, a storage medium identification number having a predetermined relationship with a storage medium identification number of the key generation right list is calculated, and added to the key generation right list. 12. The encryption method according to claim 5, wherein the master key list in the storage medium is a hierarchy to which a user who owns the storage medium belongs among the master keys whose secret numerical values are different for each user hierarchy. An encryption method characterized by being configured only by the hierarchy-specific master key that is the master key of. 13. The encryption method according to claim 12, wherein when a data key is generated inside the storage medium when writing or reading a file to or from the storage device, the storage medium identification is included in the key generation right list. An encryption method, characterized in that the master key of the lowest hierarchy of the hierarchies to which the user including the number belongs is calculated from the hierarchy-specific master key and used. 14. The encryption method according to claim 1, wherein each storage medium further stores a personal identification number of an owner of the storage medium, and a data key is stored inside the storage medium. A cryptographic method characterized in that, when calculating, the storage medium identification number and the personal identification number are used to check whether or not there is a right to calculate a data key. 15. A plurality of terminals connected to each other by a communication network, and a storage device accessible from the plurality of terminals.
An information communication system comprising: a storage medium that is connectable to the terminal and has a calculation function that is distributed to users in advance, and that encrypts a file on the storage device that is shared by a plurality of users. The storage medium is a master key list composed of a storage medium identification number unique to the storage medium and a plurality of secret numerical values called master keys, and a key transmitted from a terminal in the process of writing a file to the storage device. A means for receiving a generation right list, selecting a master key based on the key generation right list, generating a data key based on the selected master key and the received key generation right list, and returning the data key to the terminal; Receiving the key generation right list transmitted from the terminal in the process of reading the file from the storage device, and including the own storage medium identification number in the key generation right list. Means for checking whether the storage medium identification number included in the key generation right list is in a predetermined relationship with its own storage medium identification number, and the key generation right received by the checking means If the self-storage medium identification number is included in the list or if the self-storage medium identification number and the storage medium identification number included in the key generation right list have a predetermined relationship, based on the key generation right list Means for selecting a master key, generating a data key based on the selected master key and the received key generation right list, and returning the data key to the terminal, wherein the terminal stores a file to the storage device. In the writing process, a means for generating a key generation right list, which is a list of storage medium identification numbers representing sharers of the file to be written, and transmitting the key generation right list to the storage medium, and a means for returning from the storage medium. Means for encrypting a plaintext file using the sent data key to generate a ciphertext file, means for writing the ciphertext file, the key generation right list, and the file name in the storage device, and the storage device In the process of reading the file from the device, means for reading the ciphertext file and the key generation right list from the storage device according to the file name of the file to be read, and transmitting the read key generation right list to the storage medium. An information communication system comprising means and means for generating a plaintext file by decrypting the ciphertext file using the data key returned from the storage medium. 16. An IC card comprising a computing means, a reader / writer interface, and a storage means, wherein the storage means stores an IC card identification number unique to the IC card, and an IC is provided via the reader / writer interface. When the list of card identification numbers is received and the IC card identification number is included in the list, a data key is generated and output, and the IC card identification number is not included in the list. Also included in the list
An IC card which generates and outputs a data key when a card identification number and an own IC card identification number satisfy predetermined conditions. 17. An IC card provided with a computing means, a reader / writer interface, and a storage means, wherein the storage means has a cryptographic code in addition to a personal identification number of a cardholder used for general purposes. An IC card characterized by storing an identification number for use.