KR101648262B1 - Method for managing encrypted files based on password with secure file deleting function suitable for ssd and system for managing encrypted files using the same - Google Patents

Abstract

The encryption file management system according to the embodiments of the present invention generates a file name encryption key by a predetermined encryption key derivation algorithm based on a user password input from a user and generates a file name encryption key based on a salt An encryption key generation unit for generating a file data encryption key by an encryption key derivation algorithm, a file data encryption unit for encrypting the file data using the file data encryption key, and a file name encryption unit for encrypting the file name using the file name encryption key .

Description

TECHNICAL FIELD The present invention relates to a password-based encryption file management method having a secure deletion function suitable for an SSD, and an encryption file management system using the password-

The present invention relates to a file encryption technique, and more particularly, to a password-based file encryption technique.

Nonvolatile storage devices such as solid state drives (SSDs) have become more popular than conventional hard disk drives (HDDs) as the nonvolatile storage devices become rapidly less expensive and larger in capacity due to the development of nonvolatile device technology including flash memory. , Hard disk drive) can be replaced.

In non-volatile storage devices such as SSDs, end users do not feel much different from HDDs in use, but operations that occur at the time of actual write, read, and delete commands are inherently different from those that occur at the HDD .

The biggest difference between SSD and HDD operation is a series of operations for erasing or overwriting, garbage collection operation, wear leveling, and trim operation.

The HDD can overwrite new data at any position on the disk, in as little as a bit. On the other hand, if the SSD wants to completely delete some data and create an empty block or overwrite it with other data, first copy all the pages of the block having the page to be erased to another empty block, ). Thereafter, overwriting can be completed only by programming data of a smaller unit such as a new word, page, etc. in the erased and vacated block. Normally, empty blocks must be fully prepared in the SSD so that it can be written smoothly, so the SSD must consistently gather pieces of the file to prevent fragmentation. This is called garbage collection.

Also, since the lifetime of each cell depends on the number of write and erase cycles, the number of write and erase cycles for the blocks must be leveled to increase the life of the storage device. This is called wear-leveling.

The trim operation is an operation in which the operating system performs more active empty block creation for the SSD if the garbage collection operation is an operation in which the internal controller of the SSD creates its own empty blocks. For example, if the operating system deletes a file, then if it is a HDD, the file can be deleted only by manipulating the file entry of the file system, and new data can be overwritten at any time as an empty block on the block marked as deleted , SSD, you can not overwrite new data on the block by manipulating only the file entry. In this case, when the operating system sends a Trim command to the SSD at the time of file deletion, the SSD not only deletes the logical files in the file system of the file but also erases the blocks in which the file is recorded in a timely manner to make empty blocks. Collection to free an empty block.

According to the characteristic of the SSD alone, the security deletion method developed on the basis of the HDD conventionally allows the data to remain as it is before the controller of the SSD actually performs the garbage collection to make an empty block even if the user deletes the data with such security deletion methods. There is a problem in that it can be recovered at any time.

In addition, if the secure delete application performs the delete operation independently of the operating system to make the block occupied by the file a de facto empty block, the operating system can not prevent the block from being occupied by the file because the delete operation did not go through the operating system Or it may cause performance degradation due to erroneous operation or unnecessary operation, in which the operating system repeatedly tries to repeatedly erase a block already filled with "1 ".

On the other hand, the file encryption technology can be classified into a hardware-based method and a software-based method. The hardware-based method is a method in which a storage device incorporates a hardware encryption chip, and the storage device itself performs encryption and decryption in real time. However, a commonly used USB (universal serial bus) external drive or a Serial Advanced Technology Attachment (SATA) drive can not recognize (replugging) the data bus as long as the power line is still connected from the original host , It remains unlocked even if it is connected to the data bus of the unauthorized host since it is unlocked by the authorized host. Thus, an unauthorized host can access the encrypted SSD. This hardware-based file encryption technology is vulnerable to such hot-plug attacks.

In the case of a software based approach, the user can only encrypt the desired files or encrypt the entire drive. Encrypting the entire drive is inefficient, so it is common to encrypt files by file or by directory / folder. However, in a commonly used symmetric key encryption scheme, a password itself or an encryption key must be stored in some form somewhere, whether attached to a file or stored in a specific location provided by the operating system or application, There is a possibility. There is also the problem that filenames that can have important information about the file are not encrypted.

Likewise, when the conventional encryption method developed on the basis of the HDD is applied to the SSD as it is, there is no guarantee that the encryption key is stored somewhere in the SSD, and even if the encrypted file is deleted on the operating system, all the encryption keys are actually deleted together with the file .

First of all, since the SSD can not be overwritten immediately, when the user encrypts the original unencrypted original file to create a new encrypted file, the original data before encryption is logically deleted on the SSD, Remains substantially unchanged, so that unencrypted data can be recovered completely.

Accordingly, there is a need for a file encryption technique suitable for an SSD and a technique for securely deleting an encrypted file, overcoming these conventional problems.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a password-based encryption file management method having a security deletion function suitable for an SSD and an encryption file management system using the password-based encryption file management method.

The present invention is directed to a password-based encryption file management method capable of protecting a hot plug attack in an SSD-based storage medium and selectively encrypting only necessary files or folders, And an encryption file management system.

 The present invention provides a password-based encryption file management method capable of securely deleting data without conflict with an operating system related to an encrypted file in an SSD-based storage medium, and an encryption file management system using the method have.

The solution to the problem of the present invention is not limited to those mentioned above, and other solutions not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention,

Generates a file name encryption key by a predetermined encryption key derivation algorithm based on a user password inputted from the user, generates a file data encryption key by a salt derived from the file name and a predetermined encryption key derivation algorithm based on the user password An encryption key generation unit for generating an encryption key;

A file data encryption unit for encrypting file data using the file data encryption key; And

And a file name encryption unit for encrypting the file name using the file name encryption key.

According to one embodiment, the encryption key generator may be operable to use either the file name, the file name encryption key, or a newly derived digest from the file name encryption key as the salt for the file data encryption key.

According to one embodiment, the encryption key generator may be operable to use an identifier of a storage device in which an encrypted file is to be stored as a salt for generating the file name encryption key.

According to one embodiment, the encryption key generation unit operates based on a password-based key derivation function 2 (PBKDF2) algorithm as an encryption key derivation algorithm for generating at least one of the file name encryption key and the file data encryption key .

According to one embodiment, the encrypted file management system comprises:

Upon reading access to the encrypted file, the user password is input from the user, the decrypted file name is recovered from the encrypted file name using the file name encryption key generated from the input user password, and the decrypted file name and the user password are generated And a file decryption unit for generating decrypted file data from the encrypted file data by using a file data encryption key.

According to an embodiment, the file decoding unit may include:

Receives a user password from a user,

Obtain the encrypted file name through the file input / output system of the operating system,

Generating a file name encryption key according to the same encryption key derivation algorithm, parameters, and user password used when the file name encryption key is generated in the encryption key generator,

Restores the file name according to the same encryption algorithm used in the file name encryption unit by using the file name encryption key from the encrypted file name,

The encryption key generating unit generates a file data encryption key according to the same encryption key derivation algorithm, parameters, salt and user password derived from the restored file name, which are the same as those used when the file data encryption key is generated,

Obtains encrypted file data through a file input / output system of the operating system,

From the encrypted file data, the file data encryption key to generate decrypted file data according to the same encryption algorithm used in the file data encryption section.

According to one embodiment, the file to be encrypted or the encrypted file may be stored in a non-volatile storage device.

According to one embodiment, the encrypted file management system comprises:

Records and inspects both the entry of the file name and the address of the deletion object and the pages of the file data to be deleted with 0x00 when the user securely deletes the traces of the original file remaining after being encrypted or the user securely deletes the encrypted file itself, and deletes the entry of the file name and the address of the deletion target and the pages of the file data to be deleted. When the trimming function is terminated, both the entry of the file name and the address of the deletion target and the pages of the file data to be deleted are written with 0xFF And a file security deletion unit.

According to an embodiment, the file security erasure unit may include:

Volatile storage apparatus records both the entry of the file name and address of the deletion target recorded in the file management area of the nonvolatile storage device and the pages of the file data to be deleted stored in the data storage area of the nonvolatile storage device as 0x00,

Checks whether an entry of a file name and an address to be deleted recorded in the file management area and a page of file data to be deleted stored in the data storage area are all written 0x00,

And erasing the entry of the file name and address to be deleted and the pages of file data to be deleted in the data storage area in the file management area,

When the trimming function is terminated, an entry of a file name and an address to be deleted in the file management area and pages of file data to be deleted in the data storage area are all written at 0xFF.

According to another aspect of the present invention,

An encryption file management system running on an operating system of a computer,

Generating a file name encryption key by a predetermined encryption key derivation algorithm based on a user password inputted from a user;

Generating a file data encryption key by a salt derived from a file name and a predetermined encryption key derivation algorithm based on the user password;

Encrypting the file data using the file data encryption key; And

And encrypting the file name using the file name encryption key.

According to one embodiment, the file data encryption key comprises:

The file data encryption key may be generated using any one of the file name, the file name encryption key, or the newly derived digest from the file name encryption key as the salt for the file data encryption key.

According to one embodiment, the file name encryption key comprises:

May be generated using the identifier of the storage device in which the encrypted file is to be stored as a salt for generating the file name encryption key.

According to one embodiment, at least one of the encryption key derivation algorithm for generating the file name encryption key or the encryption key derivation algorithm for generating the file data encryption key may be based on the PBKDF2 algorithm.

According to one embodiment, the encryption file management method comprises:

Upon reading access to the encrypted file, the user password is input from the user, the decrypted file name is recovered from the encrypted file name using the file name encryption key generated from the input user password, and the decrypted file name and the user password are generated And generating the decrypted file data from the encrypted file data using the encrypted file data encryption key.

According to one embodiment, the step of generating the decrypted file data comprises:

Receiving a user password from a user;

Obtaining an encrypted file name through a file input / output system of an operating system;

Generating a file name encryption key according to the same encryption key derivation algorithm, parameters, and user password used when the file name encryption key is generated in the encryption key generator;

Restoring a file name according to the same encryption algorithm used in the file name encryption unit using the file name encryption key from the encrypted file name;

Generating a file data encryption key according to the encryption key derivation algorithm, parameters, salt and user password derived from the restored file name, which are the same as those used when the file data encryption key is generated in the encryption key generation unit;

Obtaining encrypted file data through a file input / output system of an operating system; And

And generating the decrypted file data from the encrypted file data using the file data encryption key according to the same encryption algorithm used in the file data encryption unit.

According to one embodiment, the file to be encrypted or the encrypted file may be stored in a non-volatile storage device.

According to one embodiment, the encryption file management method comprises:

Records and inspects both the entry of the file name and the address of the deletion object and the pages of the file data to be deleted with 0x00 when the user securely deletes the traces of the original file remaining after being encrypted or the user securely deletes the encrypted file itself, and deletes the entry of the file name and the address of the deletion target and the pages of the file data to be deleted. When the trimming function is terminated, both the entry of the file name and the address of the deletion target and the pages of the file data to be deleted are written with 0xFF And deleting the security information.

According to one embodiment, the step of deleting security comprises:

Recording an entry of a file name and address to be deleted recorded in the file management area of the nonvolatile storage device and a page of file data to be deleted stored in the data storage area of the nonvolatile storage device as 0x00;

Checking whether an entry of a file name and an address to be deleted recorded in the file management area and a page of file data to be deleted stored in the data storage area are all recorded as 0x00;

Erasing the entry of the file name and address to be deleted and the pages of file data to be deleted in the data storage area in the file management area by performing a trimming function; And

Recording the entry of the file name and the address to be deleted in the file management area and the pages of the file data to be deleted in the data storage area as 0xFF when the trim function is terminated.

According to the password-based encryption file management method having a security deletion function suitable for the SSD of the present invention and the encryption file management system using them, since it is a software-based encryption technique, it is robust against hot-plug attacks and selectively encrypts necessary files or folders .

According to the password-based encrypted file management method having the security deletion function suitable for the SSD of the present invention and the encrypted file management system using them, the file name can be encrypted.

According to the password-based encryption file management method having a security deletion function suitable for the SSD of the present invention and the encryption file management system using them, the encryption key for encrypting the file name and the encryption key for encrypting the file data are different, Even the data decryption is much more difficult.

According to the password-based encrypted file management method and the encrypted file management system using the security-deletion function suitable for the SSD of the present invention, the original data remaining after encryption or the encrypted data deleted by the user can be sure You can safely erase it.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a conceptual diagram illustrating an encryption file management system and method according to an embodiment of the present invention.
2 is a conceptual diagram illustrating a process of generating a file name encryption key and a file encryption key in an encryption file management system according to an embodiment of the present invention.
3 is a conceptual diagram illustrating a process of storing an encrypted file in an encrypted file management system according to an embodiment of the present invention.
4 is a conceptual diagram illustrating a process of storing an encrypted file name in an encrypted file management system according to an embodiment of the present invention.
5 is a conceptual diagram illustrating a process of reading an encrypted file in the encrypted file management system according to an embodiment of the present invention.
6 is a conceptual diagram illustrating a process of deleting an encrypted file in an encrypted file management system according to an embodiment of the present invention.

For the embodiments of the invention disclosed herein, specific structural and functional descriptions are set forth for the purpose of describing an embodiment of the invention only, and it is to be understood that the embodiments of the invention may be practiced in various forms, The present invention should not be construed as limited to the embodiments described in Figs.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

To avoid confusion throughout the description, delete refers to the logical removal of a file by the operating system, and erase refers to a hardware level operation that makes the SSD an empty block so that it can be overwritten.

Secure deletion collectively refers to a series of operations that erase data from the SSD in an unrecoverable state according to a user's command and organize the existence of the file.

Throughout this specification the terms are defined as follows.

FN: File name (filename)

FD: file data

EFN: Encrypted filename (encrypted filename)

EFD: Encrypted file data

FNK: encryption / decryption key for filename

FDK: encryption / decryption key for file data

UPW: User password (user password or passphrase)

PRF: pseudorandom function

H ⁿ (): n times iterating cryptographic hash function

H ⁿ (UPW): The hash function for encryption is repeated n times based on the user password

PBKDF2: Password-Based Key Derivation Function # 2

S _FNK : A cryptographic salt added to PBKDF2 to generate FNK.

S _FDK : Salt added to PBKDF2 to generate FDK

kLen: length parameter of encryption key

C: Number of iterations

On the other hand, unless otherwise specified, the encryption algorithm herein refers to a symmetric key encryption algorithm. Therefore, the decryption key is the same as the encryption key even if it is not mentioned separately, and the encryption key can be used as a decryption key according to the context.

1 is a conceptual diagram illustrating an encrypted file management system according to an embodiment of the present invention.

1, the encrypted file management system 10 includes an encryption key generation unit 11, a file data encryption unit 12, a file name encryption unit 13, a file decryption unit 14, and a file security deletion unit 15 ).

The encrypted file management system 10 may be implemented as part of or the driver of the operating system 20 or as a third party application operating on the operating system 20. [

First, in step S11, the encryption key generating unit 11 generates a file name encryption key FNK and a file data encryption key FDK by a predetermined encryption key derivation algorithm based on a user password UPW input from a user. Respectively.

Specifically, the encryption key generating unit 11 generates a file name encryption key FNK by a predetermined encryption key derivation algorithm based on the user password UPW, and stores the user password UPW and the file name encryption key FNK And generates a file data encryption key (FDK).

At this time, the encryption key generating unit 11 may use an algorithm different from the encryption key derivation algorithm for generating the file data encryption key (FDK) as the encryption key derivation algorithm for generating the file name encryption key (FNK) The encryption key derivation algorithms may be set to be some or all of the same kind of algorithms and parameters.

The encryption key generation unit 11 may use adaptive key derivation functions such as the PBKDF2 algorithm as an encryption key derivation algorithm. Conventional adaptive key derivation functions utilize salting and key stretching techniques when generating a digest using a one-way hash function in the seed These are functions that can prevent the digest from identifying the seed.

At this time, the salting technique is a technique of generating different digests from the same seed by applying a salt, which is a string of arbitrary predetermined unit, to a hash function together with a given seed. Even if an attacker finds the relationship between a particular seed and a particular seed that has not been solated, it is difficult to determine the correct seed from the solved digest.

The key stretching technique is a technique of generating a digest with a given seed and then repeating the operation of generating a new digest with the generated digest as a new seed. The attacker would be forced to run the hash function hundreds or thousands of times for every keyword, which is a significant hindrance.

2 is a block diagram illustrating an example of a process of generating a file name encryption key and a file encryption key of the encryption file management system according to an embodiment of the present invention. It is a conceptual diagram.

2, the PBKDF2 algorithm is based on SHA, MD5 (k), based on a pseudo-random number function PRF, a user password P, ciphertexts S _FNK , S _FDK , a repetition number parameter C and a digest length parameter kLen. The file name encryption key FNK and the file data encryption key FDK can be generated using a verified hash function such as the hash function.

In PBKDF2 algorithm of Figure 2, as, doctors and the output of the HMAC (hash-based Message Authentication Code ) function as a random number function (PRF) may be used, Salt (S _FNK) to generate the encryption key (FNK) of the file name Information such as time-invariant information relating to the storage device in which the encrypted file is to be stored, for example, the manufacturing serial number of the nonvolatile storage device 30, may be used.

The digest length parameter (kLen) is determined according to the key length used in the types of encryption algorithms to be used in the future, i.e., DES, 3-DES, AES 128, AES 192, AES 256,

The repetition number parameter C may be specified to be, for example, about 1000 times.

Depending on the embodiment, a simple hash function based on the user's password may be used for the encryption key (FNK) of the filename.

Further, in order to generate the file data encryption key FDK, the output of the HMAC function as the pseudo-random number function PRF may be used and the file name FN as salt _FDK , in some embodiments, Either a newly derived digest from the file name encryption key (FNK) or the file name encryption key (FNK) can be used.

Similarly, the digest length parameter (kLen) is determined according to the key lengths of the types of encryption algorithms to be used later, namely, DES, 3-DES, AES 128, AES 192, AES 256, For example, about 1000 times.

As Salt (S _FDK) for generating the file data encryption key (FDK) in FIG. 2 filename (FN), which point is that one is used in the newly derived digest from the file name encryption key (FNK) or file encryption key (FNK) Unusual.

The conventional file name encryption scheme is efficient because it encrypts with the same encryption key as the file data encryption key, but the user password is more likely to be identified.

However, in the present invention, since the encryption key (FNK) of the file name is different from the encryption key (FDK) of the file data, the possibility of the user password UPW being identified is low and different file names are used for different file data The encryption keys FDK of the file data are all different. Therefore, even if the attacker takes the encrypted file data, it is very unlikely to decrypt it. In addition salt (S _FDK) is the filename (FN) or the file name so derived from the encryption key (FNK), file data encryption key (FDK) or salt (S _FDK) to system 10 for this file data encryption key (FDK) There is no need to store them separately.

If there are two or more files, the encryption key generating unit 11 can generate one file name encryption key FNK and a plurality of file data encryption keys FDK as many as the number of files.

Subsequently, in step S12, the file data encryption unit 12 can encrypt the file data using the file data encryption key (FDK).

3 is a conceptual diagram illustrating a process of storing an encrypted file in an encrypted file management system according to an embodiment of the present invention.

In step S121, the file data encryption unit 12 receives the file data encryption key (FDK) corresponding to the original file to be encrypted from the encryption key generation unit 11, and in step S122, The encrypted file data EFD is input to the file input / output system (OS) 20 of the operating system 20 in step S123, and the original file data FD is input to the encryption algorithm operation unit 121 to generate encrypted file data EFD. 21).

Subsequently, the file input / output system 21 of the operating system 20 stores the encrypted file data in the predetermined data storage area 32 of the nonvolatile storage device 30.

At this time, if the original file to be encrypted is a file newly created in the main memory (RAM) and stored in the nonvolatile storage device 30 for the first time, the encrypted file management system 10 stores the encrypted file data EFD There is no further action such as file deletion to the nonvolatile storage device 30 after that.

On the other hand, if the original file to be encrypted is a file (FD) that has been stored in the non-volatile storage device 30 in an unencrypted state before the encryption instruction, the encrypted file management system 10 transmits the encrypted file data Volatile storage device 30 to the file input / output system 21 of the operating system 20 so as to store the EFD in the data storage area 32 of the nonvolatile storage device 30, It is necessary to find traces of the original file data FD stored in the original file data FD and securely delete the traces of the found original file data FD. This security deletion will be described later in more detail.

The file name encryption unit 13 can encrypt the file name FN by using the file name encryption key FNK in succession to or simultaneously with the file data encryption operation of the file data encryption unit 12 in step S13.

4 is a conceptual diagram illustrating a process of storing an encrypted file name in an encrypted file management system according to an embodiment of the present invention.

The file name encrypting unit 13 receives the file name encryption key FNK for the original file to be encrypted from the encryption key generating unit 11 in step S131, In step S133, the encrypted file name EFN is transmitted to the file input / output system 21 of the operating system 20 by inputting the file name FN to the encryption algorithm operation unit 131 to generate an encrypted file name EFN. do.

The file input / output system 21 of the operating system 20 then stores the address of the predetermined data storage area 32 of the nonvolatile storage device 30 in which the encrypted file data EFD is stored and the encrypted file name EFN, In the file management area 31 of FIG.

For example, in the NT file system (NTFS), the file management area 31 is a master file table (MFT), and the file input / output system 21 has an encrypted file name (EFN) The storage address of the file data EFD can be input to the master file table.

If the original file to be encrypted is newly created in the main memory and stored in the nonvolatile storage device 30 for the first time, the encrypted file management system 10 stores the encrypted file name (EFN) No action is taken on the storage device 30 such as filename resolution.

On the other hand, if the original file to be encrypted is a file stored in the nonvolatile storage 30 in an unencrypted state before the encryption instruction, the encrypted file management system 10 stores the encrypted file name (EFN) Volatile storage device 30 to the file input / output system 21 of the nonvolatile storage device 20, the entry or its trace found in association with the original file recorded in the file management area 31 of the nonvolatile storage device 30, 32 together with the traces of the original file data (FD). This security deletion will be described later in more detail.

When there is a read access to the encrypted file in which the file name and the file data are respectively encrypted and stored, in step S14, the file decryption unit 14 receives the user password UPW from the user, (FN) decrypted from the encrypted file name (EFN) by using the file name encryption key (FNK) generated from the user name UPW and encrypts the file data FN generated from the decrypted file name FN and the user password UPW And generates decrypted file data from the encrypted file data EFD using the key FDK.

The decrypted file name (FN) and decrypted file data (FD) may be provided to a process or user application of the operating system that called the file.

FIG. 5 is a conceptual diagram illustrating a decryption-read process of an encrypted file in the encrypted file management system according to an embodiment of the present invention.

5, the file decryption unit 14 receives the user password UPW from the user in step S141 and generates a file name encryption key FNK in the encryption key generation unit 11 in step S142 at the time of deriving the same encryption key as that used in the algorithm (PBKDF2), parameters _{(PRF, s FNK, C,} kLen) and user password generating a file name encryption key (FNK) according to (UPW), and step (S143), The encrypted file name EFN is acquired through the file input / output system 21 of the operating system 20 and the same encryption key FNK as used in the file name encryption unit 13 is obtained by using the file name encryption key FNK in step S144. And restores the decrypted file name FN according to the algorithm (AES, etc.).

Subsequently, in step S145, the file decryption unit 14 encrypts the encryption key derivation algorithm PBKDF2, the parameters PRF, The file data encryption key FDK is generated in accordance with the restored file name FN or filename encryption key FNK and user password UPW which are the passwords C and KLen and S _{FDK in} step S146, The encrypted file data EFD is obtained through the file input / output system 21 of the file server 20 in step S147 and the encrypted file data EFD is obtained from the encrypted file data EFD in step S147 by using the file data encryption key FDK And generates decrypted file data FD in accordance with the same encryption algorithm (AES or the like) used in the section 12.

Thereafter, the file decryption unit 14 may provide the decrypted file name FN and the decrypted file data FD to the process or user application of the calling operating system.

As described above, the encryption file management system 10 of the present invention includes a user password UPW, salts _SFNK , S _FDK , parameters PRF, _SFN , and _SFN for encrypting and decrypting a file name FN and file data FD. , C, kLen, a file name encryption key FNK, and a file data encryption key FDK are required. Among these pieces of information, the salt S _FNK for encrypting the file name and some parameters PRF, C, kLen are excluded It is not necessary to separately store important information necessary for encryption / decryption in either the encrypted file management system 10 or the operating system 20 or the non-volatile storage device 30. [

The file security deleting unit 15 deletes the encrypted file from the file input and output system 21 of the operating system 20 in step S15 when the user securely deletes the trace of the original file remaining after being encrypted, Writes in the file management area 31 of the nonvolatile storage device 30 an entry of the file name and address of the deletion target and the pages of the file data to be deleted stored in the data storage area 32 as 0x00 And a trim function to erase the entries of the file names and addresses to be deleted in the file management area 31 and the pages of file data to be deleted in the data storage area 32. When the trim function is completed, The entry of the deletion target file name and address and the pages of the deletion target file data in the data storage area 32 are all written as 0xFF.

Here, a nonvolatile memory such as a flash memory typically refers to the erased state as "1" and the programmed state as "0", while "1" to "0" "→" 1 "is available only when the entire block is erased.

Therefore, the operation of writing all of the specific pages at 0x00 above can be easily performed by leaving the cell that is already "0" as it is, and programming the cell which is "1" as "0".

FIG. 6 is a conceptual diagram illustrating a process of deleting an encrypted file in the encrypted file management system according to an embodiment of the present invention. Referring to FIG.

In step S151, the file security deletion unit 15 deletes the file deletion target (s) recorded in the file management area 31 of the nonvolatile storage device 30 via the file input / output system 21 of the operating system 20 Both the entry of the file name and the address and the pages of the file data to be deleted stored in the data storage area 32 are written as 0x00. In step S152, the entry of the file name and address to be deleted, It is checked whether all the pages of the file data to be deleted stored in the data storage area 32 have been written with 0x00. In step S153, a trim function is performed, The pages of the file data to be deleted are erased in the entry and data storage area 32. When the trim function is finished in step S154, And deleted in the data storage area 32, all the pages of the target file data is written to 0xFF.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. It will be understood that variations and specific embodiments which may occur to those skilled in the art are included within the scope of the present invention.

Further, the apparatus according to the present invention can be implemented as a computer-readable code on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the recording medium include ROM, RAM, optical disk, magnetic tape, floppy disk, hard disk, nonvolatile memory and the like. The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

10 Encrypting File Management System
11 encryption key generation unit
12 File data encryption unit
13 file name encryption unit
14 File Decoding Unit
15 File security deletion unit
20 Operating System
21 File I / O System
30 Nonvolatile Storage Devices
31 File management area
32 data storage area

Claims (7)

Generates a file name encryption key by a predetermined encryption key derivation algorithm based on a user password inputted from the user, generates a file data encryption key by a salt derived from the file name and a predetermined encryption key derivation algorithm based on the user password An encryption key generation unit for generating an encryption key;
A file data encryption unit for encrypting file data using the file data encryption key; And
And a file name encryption unit for encrypting the file name using the file name encryption key,
Wherein the encryption key generator is operative to use either the file name, the file name encryption key, or the newly derived digest from the file name encryption key as the salt for the file data encryption key, and the pseudo-random number function (PRF) The file name encryption key and the file data encryption key are generated using the hash function based on the encryption key P, the encryption salts S _FNK and S _FDK , the repetition number parameter C and the digest length parameter kLen The encrypted file management system.
delete The system according to claim 1, wherein the encrypted file or the encrypted file is stored in a non-volatile storage device. Generating a file name encryption key by a predetermined encryption key derivation algorithm based on a user password inputted from a user;
Generating a file data encryption key by a salt derived from a file name and a predetermined encryption key derivation algorithm based on the user password;
Encrypting the file data using the file data encryption key; And
Encrypting the file name using the file name encryption key,
(P), a password (P), a password (P), and a password (P) as a salt for the file data encryption key, and to use any one of the file name, the file name encryption key, Wherein the file name encryption key and the file data encryption key are generated by using a hash function based on the salts (S _FNK , S _FDK ), the repetition number parameter (C), and the digest length parameter (kLen) Way.
delete The method according to claim 4, wherein the file to be encrypted or the encrypted file is stored in a non-volatile storage device. A computer-readable recording medium having embodied thereon a computer program for implementing a method of managing an encrypted file according to any one of claims 4 and 6.

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