KR950015185B1 - Personal computer data protection method using automatic encryption/decryption - Google Patents

Abstract

The data protecting method of a personal computer using an automatic coding/decoding comprises the steps of: performing a mandatory access control to determine if it is related to coding/decoding if a user inputs a command in a user command standby state; determining the coding/decoding to permit a read access to a corresponding file only when a secret grade of a user is higher than or equal to the secret grade of to-be-accessed file and the secret range of a user contains the secret range of the to-be-accessed file; generating a coding key by using the size of the file as a coding initial vector or generating a decoding key by using it as a decoding initial vector; and decoding corresponding file by inserting the decoding key and the decoding initial vector into a coding file to tout a decoded file to the user and performing a coding by the generated coding key to output a coding file.

Description

Data protection method of personal computer using automatic encryption / decryption

1 is a block diagram of a hardware system to which the present invention is applied.

2 is a block diagram of a software block of automatic encryption / decryption and method.

3 is a detailed configuration diagram of an automatic encryption / decryption unit.

4 is a process flow diagram for an automatic encryption / decryption method according to the present invention.

* Explanation of symbols for main parts of the drawings

1: auxiliary memory 2: main memory

3: access control unit 4: command interpreter

5: automatic encryption / decryption unit 6: encryption / decryption key generation unit

21: encryption / decryption reading unit 22: encryption unit

23: decoder

The present invention provides a method of preventing leakage of system resources of a malicious user, especially information about a file, due to the inherent characteristics of a personal computer in a personal computer system that stores and processes data. A data protection method of a personal computer using automatic encryption / decryption to prevent leakage of important data in the personal computer based on an automatic encryption / decryption system.

In general, the prevention of illegal information leakage of an existing personal computer relies only on random access control of a file by maintaining a profiling list for each file, or relies on encryption of a file by a user's command input. have. However, since discretionary access control (DAC) is based solely on access to system resources based on the user's identifier (ID), the DAC mechanism is a method of maintaining information for multiple levels of confidentiality of data. It does not have access control based on multiple secret classes of such data.

In addition, since the user's identifier is very important as described above, if any malicious user can use the identifier of another user to access certain material in the personal computer, the access control by the DAC is not secure. There is no guarantee. In addition, due to the inherent characteristics of the personal computer, there is a mechanism for bypassing such access control to directly access important files existing in the auxiliary storage. To solve this problem, the encryption / decryption method provided by the user's command input is also encrypted when the user has to enter the encryption / protection key and the command and the encryption / decryption key is lost. There was a problem in that the file could not be decrypted again and a double encryption could occur due to a user error.

Therefore, the present invention devised to solve all the problems of the prior art is based on the mandatory access control (MAC: Mandatorly) for the file based on the user's secret label (secret class + secret category) and the confidentiality of the data contained in the file The purpose of the present invention is to provide a data protection method of a personal computer using automatic encryption / decryption to prevent illegal leakage of information from malicious users by interlocking with automatic encryption / decryption after performing Access Control.

In order to achieve the above object, the present invention provides a main memory device, a command interpreter connected to the main memory device, an access control unit connected to the command interpreter, an access control unit, an auxiliary memory device and an automatic device connected to the main memory device. A data protection method of a personal computer comprising an encryption / decryption unit, an automatic encryption / decryption key generation unit connected to the automatic encryption / decryption unit, and a protection storage unit connected to the automatic encryption / decryption unit and a main memory device. Access when a user enters a command while waiting for a user command to execute a shell process, and intercepts all system calls in the automatic encryption / decryption unit linked with access control to determine whether encryption / decryption is involved. The first step of performing; If the user's secret level is higher than or equal to the secret level of the file to be accessed and the user's secret category contains the secret category of the file to be accessed, the read / write access to the file is allowed. A second step of determining decryption; Based on the encryption / decryption judgment, the file is forcibly closed to obtain a file size, and then an encryption key is generated using the file size as an encryption initial vector or a decryption key is used as a decryption key and decryption initial vector value. Third step to do; And injecting the generated decryption key and decryption initial vector into an encryption file to decrypt the corresponding file, outputting the decrypted plain text file to the user, and encrypting the file with the generated encryption key to output the encrypted file. And a fourth step.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

1 is a configuration diagram of a hardware system to which the present invention is applied, in which 1 is an auxiliary storage device, 2 is a main memory device, 3 is an access control unit, 4 is a command interpreter, 5 is an automatic encryption / decryption unit, and 6 is an arm. / Decryption key generator respectively.

Hardware system to which the present invention is applied is as shown in the drawings, a storage for storing the access control information of the user, a storage for storing the access control information of the file, a storage for storing instructions and data for encryption / decryption A main memory (2) configured by integrating a storage device, a command interpreter (4) connected to the main memory (2) to make a permission decision for a read access request, and a command secret (4) connected to the command interpreter (4). Compares the values between them by referring to the secret class of < RTI ID = 0.0 > and < / RTI > Automatic encryption / decryption that performs encryption / decryption by reading and recording request, and decrypts at the read request date and encrypts at the write request date. An encryption / decryption key generation unit 6 connected to the automatic encryption / decryption unit 5 and the automatic encryption / decryption unit 5 to generate and store a key used for encryption and decryption; A secondary storage device 1 is connected to the automatic encryption / decryption unit 5 and the main memory device 2, which stores secret grade information encrypted / decrypted data of a data file.

The operation of the hardware system configured as described above is as follows.

The identifier of the user and the user secret label are stored in the storage of the main storage device 2, and the owner identifier of the file and the access permission profiling list and the secret label of the file are stored in the auxiliary storage device 1. Is stored in the storage of the main storage device 2 from the directory entry of the " The user command is sent from the command store of the main storage 2 to the command interpreter 4 and is first controlled by the access control unit 3. If the command sent is a write request, it first checks whether it has write access.

The access control unit 3 compares the values between the user's secret label and the file's secret label, and records if the user's secret level is equal to the file's secret level and the file's secret category contains the user's secret category. Access is granted. In a manner similar to the above, when a user requests read access to an important file, the access control unit 3 determines that the user's secret level is greater than or equal to the file's secret level and that the user's secret category is the file's secret. Including a category allows read access requests.

When the user attempts to access the important file as described above, if the access is granted by the access control unit, automatic encryption / decryption is finally made. That is, the automatic encryption / decryption unit determines the encryption / decryption according to the read and write request of the user's important file, and decrypts the read request and encrypts the write request. At this time, the key used for encryption / decryption is generated by the encryption / decryption key generator and performs encryption / decryption of the file using the generated key. The encryption key maintains one primary key per personal computer using a random number in the encryption / decryption section, but encrypts / decrypts all files with one key to reduce the impact of the cryptographic secretity being attenuated. Is used as the initial vector value of encryption / decoding. If a key change request is generated, a random number generation routine in the encryption / decryption key generation unit 17 is driven to change the encryption / decryption key.

2 is a block diagram of software blocks of the automatic encryption / decryption method according to the present invention, in which 11, 11a and 11b are users, 12, 12a and 12b are application programs, 13 are software library interface functions, and 14 are system calls. An interface, 15 is an access control unit, 16 is a secret class management unit, 17 is an encryption / decryption key generation unit, 18 is an automatic encryption / decryption unit, 19 is a basic input / output system, and 20 is an auxiliary storage device.

As shown in the figure, the software of the automatic encryption / decryption method according to the present invention has a legitimate user's request when requesting access to a resource (file) through the software library interface function 13 and the system call interface 14 of the user. The automatic encryption / decryption unit 18 interworking with the access control unit 15 and the encryption / decryption key generation unit 17 which generates and stores a key necessary for encryption / decryption only when the user's request is justified. . The users 11, 11a and 11b of the personal computer wish to protect via their operating programs 12, 12a and 12b, the software library interface function 13 system call interface 14 or the basic input / output system 19. A secondary memory device containing important data is reached, wherein all access requests except the direct file access through the basic input / output system 19 are first controlled by the access control unit 15.

When the user wants to access an important file, the access control unit 15 first intercepts a user's system call and determines whether the user requests a read or write request for the important file. At this time, the determination of the read or write request is made by looking at the parameters of the system call generated to access the important file. In other words, when accessing an important file, it is checked whether it is in read mode or write mode when the important file is opened. When the secret category of the user is greater than or equal to and includes the secret category of the file, reading is allowed. At this time, the automatic encryption / decryption unit 18 is called to decrypt the file.

Decryption of a file is performed using a value obtained by driving a random number generation routine in the encryption / decryption key generation unit 17 as an encryption / decryption key and using a file size as an initial vector value.

When the user opens the important file in the recording mode, the access control unit 15 allows the record access to the important file if the user's secret level is equal to the file's secret level and the file's secret category contains the user's secret category. Done. At this time, the access control unit 15 notifies the encryption / decryption reading unit 21 that the user's request is in the recording mode, and decodes the file. At this time, if the file is created for the first time, the process of decryption is omitted, and the decryption key acquisition method of the encrypted file is processed as described above, and the user applies an arbitrary operation (update, addition, etc.) to the decrypted file. Afterwards, the automatic encryption / decryption unit 18 is called when the opened file is closed to store the file.

The automatic encryption / decryption unit 18 forcibly closes the file to obtain the information necessary for encryption (that is, the size of the file) and uses the encryption as an initial vector value of the encryption / decryption key generator 17 Encryption is performed using the key stored in

Here, the illegal access attempt to directly access the file to be protected stored in the auxiliary storage device 20 through the basic input / output system 19 does not go through the automatic encryption / decryption unit applied in the present invention. Since the encryption / decryption is not performed on the file, the desired file cannot be viewed properly. As described above, the compulsory access control that reinforces the vulnerability of the conventional discretionary access control when the user requests access to the important file is controlled to compensate for the weakness of the personal computer by controlling the access request and performing automatic encryption / decryption. This ensures the security of confidential data and prevents the leakage of illegal data.

3 is a detailed configuration diagram of an automatic encryption / decryption unit, where 21 is an encryption / decryption reading unit, 22 is an encryption unit, and 23 is a decryption unit.

As shown in the figure, the automatic encryption / decryption unit 18 includes an encryption / decryption reader 21, an encryption / decryption reader 21 which first performs encryption / decryption readout for every strict access request that has passed through the access control unit 15 as shown in the figure. And an encryption unit 22 and a decryption unit 23 that perform decryption.

The encryption / decryption reader 21 intercepts the system call when the user tries to access the file through the system call interface, and determines whether encryption or decryption is necessary according to the parameter (read or write) of the system call. The encryption unit 22 receives an encryption key from the encryption / decryption key generation unit 17 when the result read by the encryption / decryption reading unit 21 is a write access to the file, and initializes the size of the file. Encryption is performed on the target file to be accessed using the vector value, and is stored in the encryption / decryption key generation unit 17 when the result read by the encryption / decryption reading unit 21 is read access to the file. The decryption unit 23 decrypts the file using the decryption key and the size of the file as the initial vector value of decryption.

4 is a process flow diagram for an automatic encryption / decryption method according to the present invention.

First, a user who wants to use a personal computer enters a command in a standby state of a user command in which a cell process is executed (31). In this case, an automatic encryption / decryption unit that interlocks all system calls for input of the user command input with access control. Intercepted at (5) (32).

The automatic encryption / decryption unit 5 determines whether the user's system call is related to the encryption / decryption of the file (open, create, or close). If it is related to encryption / decryption, the corresponding action is taken. The automatic encryption / decryption unit 5 first examines the access right to the target file to be accessed (33). If the access right is read access, the user's secret level is higher than or equal to the secret level of the access target file, and the user's secret is checked. Read access to the file is allowed only if the category contains the secret category of the file to be accessed, which is used as the basis for the encryption / decryption decision (34). That is, when the access request is read from the file, the encryption / decryption reading unit 21 requests a decryption key to read the encrypted data stored in the auxiliary storage device 1 of FIG. 1 as requested by the user. The encryption / decryption key generation unit 6 of FIG. 1 acquires the size of the file used as the decryption key and decryption initial vector value stored therein (39). The automatic encryption / decryption unit 5 of FIG. 1 reads the encryption file stored in the auxiliary storage device 1 into the automatic encryption / decryption area in the main storage device 40, and the decryption key obtained above. And injecting the initial vector into the cipher file to perform decryption on the file (41) and outputting the decrypted plain text to the user (42).

In addition, when a user requests write access for a file, first, the user system call is intercepted as above to be examined for access rights. The write access request includes a write access request for a file that already exists and a newly created file. There are two types of write access requests (i.e., post-production) write requests. First, the write access request for the existing file is decoded as described above with respect to the existing file. If the user closes the file after proper manipulation (update, change, etc.) of the decrypted file is made, the automatic encryption / decryption unit intercepts this system call. The automatic encryption / decryption unit forcibly closes the file to obtain the file size and uses it as the encryption initial vector (35).

Obtain the encryption key stored in the initial vector and the encryption / decryption key generation unit obtained above (35) and read the file in the secondary storage device into the encryption / decryption area of the main memory device (36) to perform encryption of the file. (37) The encrypted file is used as an auxiliary memory in the encryption / decryption area of the main memory (38). In addition, when a write access request for a newly created file is requested, an automatic encryption / decryption unit intercepts a system call when a user calls a generated system, displays a newly generated file, and skips the decoding process. After that, when the user finishes the proper operation on the newly created file, the file is encrypted by intercepting the close system call of the file as described above.

The present invention, which is configured and operated as described above, is significantly different from the user's input of an instruction and a key for encryption, with the introduction of a MAC technique that compensates for the shortcomings of the DAC function provided in the conventional personal computer system. By performing automatic encryption / decryption according to the access result, it is possible to increase user's convenience, eliminate data recovery due to loss of encryption key, prevent illegal leakage of important information, and assist with personal characteristics of personal computer. Since information leakage can be prevented even when direct read / write access to the memory device, various security-related accidents such as illegal copying and use of important information can be prevented.

Claims (1)

A command interpreter (4) connected to the main memory (2), the main memory (2) to make a decision to grant a read access request, and a command interpreter (4) to compare the user's secret level with the file's secret level. An access control unit 3 for controlling write access, an access control unit 3 and a main storage unit 2, an encryption / decryption reading unit 21 and an encryption unit 22 that performs encryption and decryption, and decryption. An automatic encryption / decryption unit 5 having a unit 23, and an encryption / decryption key generation unit 6 connected to the automatic encryption / decryption unit 5 to generate and store a key used for encryption and decryption. And data protection applied to hardware having a secondary storage device (1) connected to the automatic encryption / decryption unit (5) and the main memory device (2) for storing secret grade information of the data file and storing encrypted / decrypted data. Method, a shell process When a command is input in a waiting state of a user command to be executed, mandatory access control for intercepting all system calls by the automatic encryption / decryption unit 5 linked with access control to determine whether encryption / decryption is related. First steps 31 to 33 to perform; If the user's secret level is higher than or equal to the secret level of the file to be accessed and the user's secret category includes the secret category of the file to be accessed, the read access to the file is allowed. A second step 34 of determining decryption; Based on the encryption / decryption judgment, the file is forcibly closed to obtain a file size, and then an encryption key is generated using the file size as an encryption initial vector or a decryption key is used as a decryption key and decryption initial vector value. Third step (35,39) to make; And injecting the generated decryption key and decryption initial vector into an encryption date, decrypting the corresponding file, outputting the decrypted plain text file to the user, and encrypting the file with the generated encryption key to output an encrypted file. And a fourth step (36 to 38, 40 to 42). The data protection method of the personal computer using automatic encryption / decryption.