Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
  • G06F21/60—Protecting data
  • G06F21/62—Protecting access to data via a platform, e.g. using keys or access control rules
  • G06F21/6209—Protecting access to data via a platform, e.g. using keys or access control rules to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
  • G06F12/14—Protection against unauthorised use of memory or access to memory

Definitions

• the disclosed invention is generally directed to computer security systems, and more particularly to a computer system that wherein files stored on a data storage device are individually encrypted.
• a commonly utilized element of computer security is encryption whereby information is encrypted in accordance with a predetermined "key" and decryption requires knowledge of the key.
• a computer disk drive can be encrypted to make access to the information contained on the drive more difficult.
• data communicated between computer systems can be encrypted so that the communication would be more difficult to understand if intercepted.
• a consideration with known techniques of encryption at the communication level includes degraded performance due to the need for encryption of the information to be trans ⁇ mitted. Further, to the extent that the received informa- tion is to be stored on an encrypted data storage device, all of the information stored on the device including the received information would have to be encrypted, after the contents of the data storage device and the received information are initially decrypted.
• a computer data storage system that includes a data storage device, and a processor for encrypting file data to produce encrypted file data and writing the en ⁇ crypted file data to a computer file on the data storage device, wherein the computer file includes a file informa ⁇ tion header that contains information indicating that the computer file contains encrypted file data.
• the processor further reads and decrypts the encrypted file data.
• FIG. 1 is a schematic block diagram of a computer system in which file encryption in accordance with the invention can be implemented.
• FIG. 2 is a schematic depiction of the logical organi ⁇ zation of an encrypted computer file in accordance with the invention.
• FIG. 3 is a simplified flow diagram that schematically depicts the logic flow of an illustrative example of file encryption in accordance with the invention.
• FIG. 1 schematically depicted therein by way of illustrative example is an overall block diagram of a computer hardware system in which file encryp- tion in the invention can be implemented.
• the system
• ⁇ includes a central processor unit 11 which performs general digital operations for the computer system and a primary storage memory 13 which stores data and programs including processes which when executed by the central processor unit 11 implement file encryption in accordance with the inven ⁇ tion.
• the primary storage memory 13 can include in accordance with conventional techniques random access memory as well as read only memory.
• the computer system further includes peripheral devices 15 such as a display 15a, a keyboard 15b, a data storage device 15c, a printer 15d, and a modem 15e.
• a data bus 17 provides for communication between the processor, the primary storage memory, and the peripheral devices.
• a computer file is stored on the data storage device 15c in encrypted form wherein encryption is performed at the file level such that encryption and decryption are performed on a file by file basis.
• an encrypt ⁇ ed computer file is stored in a logical form of encrypted file data 51 (e.g., programs and user data) and a non- encrypted file header 53.
• the file header 53 includes file control information such as operating system type 55 and a pointer 57 that points to the encryption key for the encrypted file data or one or more other pointers to the encryption key for the encrypted file data.
• the file data 51 contains user information such as a program or data, and can also contain further control information such as security access control labels.
• FIG. 3 set forth therein is a schematic flow diagram of the logic flow of an illustrative example of a file encryption procedure in accordance with the invention.
• the procedure of FIG. 3 is implemented by execution of one or more appropriately configured programs by the central processor unit 11 of FIG. 1.
• an application program makes a file operation call to the operating system utilized in the computer system of FIG. 1, and at 113 the file operation call is intercepted.
• a file operation call is typically a call to an operating system routine that performs a conventional file operation such as create, open, read, write, and close.
• intercept mecha ⁇ nism Techniques for interception of operating system calls are well known in the art, and the particular nature of the intercept mecha ⁇ nism will depend on the particular operating system with which the invention is implemented, and can involve, for example, redirecting file operation calls to routines of the invention.
• a file information header for the file is written on the data storage device in the data blocks allocated for the file, and at 121 control returns to the calling application program.
• the term "normal" in the context of a file operation routine refers to a standard or built-in routine contained in a computer operating system for performing operations associated with or requested by a file operation call. If the determination at 115 is no, at 123 a determina ⁇ tion is made as to whether the application program making the intercepted file operation call is exempt from the need to decrypt the file that is the subject of the intercepted file operation call. For example, a file copy program or a file transfer program can operate on files without decryption.
• exempt applications would include electronic mail applications, back-up applications, and an application that implements the subject invention. If the determination at 123 is yes, at 125 a call is made to the normal file operation routine that would have been called if the intercepted file operation call had not been intercepted.
• the file information header for the file that is the subject of the intercepted file operation call is read.
• a determi- nation is made as to whether the intercepted file operation call is a write to file. If yes, at 131 the file data to be stored is encrypted to form encrypted file data, and the encrypted file data is written to the data storage device.
• file data can include file control labels as well as user data such as a program or data.
• the encryption and write operations are performed, for example, by encrypting the file data one portion at a time, buffering each encrypted file data portion in a file buffer, which can be contained in the memory 13 of FIG. 1, and calling the normal write to file routine to write the buffered encrypted file data portion to the data storage device.
• a deter ina- tion is made as to whether the intercepted file operation call is a read. If yes, at 129 the file that is the subject of the intercepted file operation call is read and decrypted.
• the reading and decryption of the file can be achieved, for example, by calling the normal read file routine to read the encrypted file data into a file buffer, which can be contained in the memory 13 of FIG. 1, and then decrypting the buffered encrypted file data to produce decrypted file data.
• the encrypted file data is read into the file buffer one portion at a time, wherein the portion read is of a fixed size.
• control returns to the application program that made the intercept ⁇ ed file operation call.
• control is trans ⁇ ferred to the normal file operation routine that would have been called had the intercepted file operation call not been intercepted.
• the foregoing procedure essentially intercepts each file operation call and determines whether operations related to encryption and decryption of a file that is the subject of the file operation call are required. If not, the normal file operation routine that would have been invoked by the intercepted file operation call is invoked. If operations related to encryption and decryption are required, the procedure of the invention performs such operations which include encrypting file to be written to the data storage device, invoking the normal file operation routine to write encrypted file data to the data storage device, invoking the normal file routine to read the encrypted file data from the data storage device, and decrypting the encrypted file data read from the data storage device.
• a determina ⁇ tion is made as to whether the existing file is encrypted, which can be determined, for example, from a catalog or directory record if a provision is made to include encryp- tion status in the catalog or directory record, or alterna ⁇ tively, the file can be read to determine whether it includes a file information header as described above relative to FIG. 1. If the existing file is not encrypted, the normal file operation is invoked by a call to the file operation routine that would have been called had the intercepted file operation call not been intercepted.
• the foregoing has been a disclosure of a computer file encryption scheme that encrypts files on a file by file basis, which advantageously allows files to be individually encrypted and decrypted without the need to encrypt and decrypt the entire contents of a data storage device, and without intervention by the user.
• the encryption scheme of the invention allows different files on the same storage device to have different encryption keys, which provides for increased security and reduces the amount of informa ⁇ tion that becomes vulnerable should an encryption key become inappropriately known. Also, only selected computer files are decrypted at any given time, which maintains the security of the remaining files.

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Publications (1)

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Citations (2)

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• 1995
  • 1995-05-19 EP EP95920547A patent/EP0715734A1/en not_active Withdrawn
  • 1995-05-19 JP JP8503140A patent/JPH08509087A/ja not_active Withdrawn
  • 1995-05-19 KR KR1019960701005A patent/KR960705275A/ko not_active Application Discontinuation
  • 1995-05-19 WO PCT/US1995/006329 patent/WO1996000942A1/en not_active Application Discontinuation
  • 1995-05-19 CA CA002165649A patent/CA2165649C/en not_active Expired - Fee Related
  • 1995-05-19 AU AU25967/95A patent/AU2596795A/en not_active Abandoned
• 1996
  • 1996-02-28 NO NO960817A patent/NO960817L/no not_active Application Discontinuation

Patent Citations (2)

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