Abstract:
The present invention discloses a data access method accomplished by the following steps of: creating a predetermined password; generating a first encryption key; encrypting data based on the first encryption key; prompting for the predetermined password upon receipt of an access request; decoding a header of the NAND flash memory based on a user-entered password; examining the header to determine whether a mapping between the user-entered password and the first encryption key is defined; and decrypting and outputting the data by a decryption key when the mapping between the user-entered password and the first encryption key is defined.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a data access method, and more particularly, to a secure data access method for applications in a data storage apparatus. 
       BACKGROUND OF THE INVENTION 
       [0002]    Revolutionary changes in our communication vehicles brought about by the amazing growth of the Internet and the ever-increasing digitization of information, pose unprecedented threats to personal security and privacy. An increasing amount of sensitive information is now circulating in electronic form, including E-mails, facsimile messages, telephone conversations, fund transfers, trade secrets and other personal records. The same technological advances have brought enormous benefits to humankind, but also make us more vulnerable to unwanted and potentially dangerous snooping. A number of new applications for those computer storage devices have emerged, and many of these have a need for enhancing the overall security of information stored in the computer storage devices. 
         [0003]      FIG. 1  to  FIG. 3  are schematic diagrams of a secure storage device and operation of the same according to U.S. Pat. No. 6,880,054 to Cheng et al. The flash memory  4 , as shown in  FIG. 1 , is divided into a number of different sections or zones. Typically, the flash memory is divided into two zones: zone  1  is for setting a software serial number, and zone  2  is used typically for storing a user&#39;s data. Besides, each zone has a unique password. Referring now to  FIG. 2 , it is a flow diagram showing the initial set-up of a password for zone  2  of the flash memory  4  by an end user. To set up the password for zone  2  the user plugs in  20  the device  10  into a USB port on the computer and communication  21  is established between the computer and the device  10 . The user then runs the driver software and the driver software enters a password installation set-up mode  23  for zone  2 . The user then enters  28  a password that they wish to use to prevent unauthorized access to zone  2  of the flash memory  4 . The password entered is then encrypted  29  and stored  30  in the flash memory  4 . 
         [0004]    After an end user has performed the initial password set up procedure described above and shown in  FIG. 2 , when the user selects zone  2  to access data stored in the flash memory  4  (see  FIG. 3 ), the micro-controller  3  sends a command to the computer to request  46  the user to enter the password for zone  2 . When the user enters the password, the computer sends the password to the micro-controller  3 . The micro-controller  3  retrieves the password for zone  2  from the flash memory  4 , decrypts  47  the password and compares it with the password entered by the user. If the password entered by the user is incorrect, the operation returns to step  46  and the computer requests  46  the user for the password again. If the password entered by the user is correct, the user has access to zone  2  of the flash memory  4  to read data from the flash memory  4  and to write data to the flash memory  4 . However, data can only be written to the flash memory  4  if the manual switch  7  is in the position to permit data to be written to the flash memory  4 . In order to read or write data from or to the flash memory  4  a read or write command is sent  48  by the computer in USB format to the micro-controller  3 . In response to the read or write command the micro-controller  3  either retrieves  49  data from the flash memory  4  and sends it to the driver  2  for conversion  50  to PC format and then to be output to the computer or receives data from the driver to write it to the flash memory  4 . The micro-controller  3  then determines  51  whether the read or write operation is complete. If the operation is not complete it returns to step  49 . If the operation is complete the operation terminates  52 . 
         [0005]    While U.S. Pat. No. 6,880,054 employs the method of comparing the user-supplied password and the stored password to limit access to the data in the flash memory, the disadvantage is that code breakers eventually decipher the password through “trial-and-error” time after time. Besides, once the flash memory  4  stored with the password is compromised or dismantled, malicious code breakers can easily access the data. Therefore, the prior art could not ensure the utmost confidentiality of the data in the storage device. Hence, there is a resulting need for a secure data access method to avoid potential leakage of the private data. Unlike conventional data access method, such as that of U.S. Pat. No. 6,880,054, the present invention takes a step ahead in enhancing the confidentiality of the digital data through generation of a password-based encryption key, and further encrypting the pre-stored data into ciphertext with the encryption key, to eliminate chances of intruders deciphering the key after many times of “trial-and-error”. 
       SUMMARY OF THE INVENTION 
       [0006]    In light of the prior art limited by the above problems, it is an object of the present invention to provide a secure data access method for use with a data read/write device. 
         [0007]    In accordance with an aspect of the present invention, a data access method applied in a data storage apparatus having at least one NAND flash memory for use with a data read/write device, a data access method comprising the steps of: a) creating a predetermined password; b) generating a first encryption key; c) encrypting data based on the first encryption key; d) prompting for the predetermined password upon receipt of an access request; e) decoding a header of the NAND flash memory based on a user-entered password; f) examining the header to determine whether a mapping between the user-entered password and the first encryption key is defined; and g) decrypting and outputting the data by a decryption key when the mapping between the user-entered password and the first encryption key is defined. 
         [0008]    Preferably, the decoding step comprises step of translating the user-entered password into a second encryption key for decoding the header. 
         [0009]    Preferably, the data access method further comprises step of prompting for the predetermined password when the mapping between the user-entered password and the first encryption key is not defined. 
         [0010]    Certainly, the first and second encryption keys translated from the passwords can be accomplished by software or hardware. 
         [0011]    Typically, the header comprises a first logical block. 
         [0012]    Certainly, the first and second encryption keys can be revised by the data read/write device. 
         [0013]    Certainly, the decryption key can be revised by the data read/write device. 
         [0014]    Alternatively, the first and second encryption keys each has a length of 64 bits, 128 bits, 192 bits, or 256 bits. 
         [0015]    Alternatively, the decryption key has a length of 64 bits, 128 bits, 192 bits, or 256 bits. 
         [0016]    Certainly, the data are encrypted according to Advanced Encryption Standard (AES), Data Encryption Standard (DES), Triple-DES, and RSA. 
         [0017]    Alternatively, the data storage apparatus includes a Universal Serial Bus (USB) PenDrive, a Smart Digital (SD) card, a MultiMedia Card (MMC), a Compact Flash (CF) card, and a USB flash drive. 
         [0018]    In accordance with another aspect of the present invention, a data access method for a data storage apparatus having at least one NAND flash memory in communication with a data read/write device comprises the steps of: prompting for a predetermined password upon receipt of an access request for data; translating a user-entered password into an encryption key; decoding a header of the NAND flash memory based on the encryption key; examining the header to determine whether a mapping between the user-entered password and a predetermined encryption key is defined; and decrypting and outputting the data by a decryption key when the mapping between the user-entered password and the predetermined encryption key is defined. 
         [0019]    Preferably, the predetermined encryption key is translated in accordance with the predetermined password. 
         [0020]    Preferably, the data access method further comprises step of prompting for the predetermined password when the mapping between the user-entered password and the predetermined encryption key is not defined. 
         [0021]    Certainly, the encryption key and the predetermined encryption key translated from the passwords can be accomplished by software or hardware. 
         [0022]    Typically, the header comprises a first logical block. 
         [0023]    Certainly, the encryption key and the predetermined encryption key can be revised by the data read/write device. 
         [0024]    Certainly, wherein the decryption key can be revised by the data read/write device. 
         [0025]    Alternatively, the encryption key and the predetermined encryption key each has a length of 64 bits, 128 bits, 192 bits, or 256 bits. 
         [0026]    Alternatively, the decryption key has a length of 64 bits, 128 bits, 192 bits, or 256 bits. 
         [0027]    Certainly, the data are encrypted according to Advanced Encryption Standard (AES), Data Encryption Standard (DES), Triple-DES, and RSA. 
         [0028]    Alternatively, the data storage apparatus comprises a USB PenDrive, a SD card, a MMC, a CF card, and a USB flash drive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0029]    The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0030]      FIG. 1  is a schematic block diagram of a data storage device according to the prior art; 
           [0031]      FIG. 2  is a flow diagram showing the initial step of the data storage device by an end user according to the prior art; 
           [0032]      FIG. 3  is a flow diagram showing operation of the prior data storage device; 
           [0033]      FIG. 4  is a schematic diagram of a data storage apparatus according to the present invention; and 
           [0034]      FIG. 5  is a flowchart of controlling data access according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]    The present invention discloses a data storage apparatus and a data access method for application in the same. The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description. The present invention needs not be limited to the following embodiments. 
         [0036]    Please refer to  FIG. 4 . It illustrates a secure architecture of a data storage apparatus according to the present invention. As shown in  FIG. 4 , the data storage apparatus  1  includes an interface  20  coupled to a data read/write device (not shown) for data buffering and transmitting therebetween, a non-volatile memory  21 , a flash memory  22  for storing data, an encryption unit  23 , and a decryption unit  24 , which would be expatiated in the follow-up descriptions. 
         [0037]    The non-volatile memory  21  is stored with an encryption key and a decryption key. Each of the keys is a field of bits used to encrypt and decrypt data using techniques known to those of skill in the art. By adoption of cryptograph algorithms, the above-identified keys are generated on the basis of a user-supplied password, usually a combination of number digits. By applying the bit values of the keys to those of the data and conducting logical operations associated with selected encryption algorithms, inclusive of Advanced Encryption Standard (AES), Data Encryption Standard (DES), Triple-DES, and RSA (Rivest-Shamir-Adleman), the encryption unit  23  and the decryption unit  24  are operable to perform encryption and decryption of the data in accordance with the encryption key and decryption key. Certainly, both keys can be revised by the read/write device. In this embodiment, both keys are ‘symmetrical’ (both encryption and decryption use the same key), yet in alternate embodiments, both keys can be ‘asymmetrical’ (encryption and decryption keys are different). Each of the key is encrypted and decrypted at the 128-bit level in this embodiment, while the 64-bit, 196-bit, or 256-bit key is acceptable to implement the present invention. In addition, the flash memory  22  includes a header portion  221 , containing a BIOS Parameter Block (BPB). The BPB is used to describe file system format of a disk volume. Typical file systems with BPB include FAT (File Allocation Table)  16 , and FAT 32 . BPB keeps important file system parameters so that BIOS (Basic Input Output System) can use those parameters to access the data stored in the disk. There is an 8-byte field in the BPB identifying the file system type, and a string for the first 3 bytes of this field must be of “FAT” in this embodiment, to verify the file system as a correct FAT file system. In alternate embodiments, the specific string(s) for that field of BPB can be located in a similar way for NTFS or other non-FAT file systems. 
         [0038]    According to the present invention, the flash memory  22  built in the storage apparatus  1  has one-way communication with the encryption unit  23  and the decryption unit  24 , during the operations of encrypting and decrypting data, respectively. The flash memory  22  is dedicated to receiving the encrypted data from the encryption unit  23  after the encryption operation, while transmitting the encrypted data to the decryption unit  24  prior to the decryption operation. The encryption unit  23  utilizes the encryption key of the non-volatile memory  21  for data encryption. Likewise, the decryption unit  24  utilizes the decryption key of the non-volatile memory  21  for data decryption. 
         [0039]    In  FIG. 5 , it illustrates a preferred embodiment of a data access method for a data storage apparatus according to the present invention. In this embodiment, the data storage apparatus of the present invention and a read/write device are employed. Alternate embodiments may use additional or different facilities to perform the operation. 
         [0040]    The data storage apparatus  1 , such as a USB flash drive, is coupled to a read/write device through an interface  20  for data stream therebetween. As shown in step S 30  of  FIG. 5 , a password is entered and a data is transmitted through the read/write device to initiate the following implementation of the present data access method. In this embodiment, a given algorithm, AES is employed for implementing data encryption, thus the encryption and decryption use a single key. Namely, encryption and decryption keys are ‘symmetrical’ (both encryption and decryption use the same key). In alternate embodiments, both keys can be ‘asymmetrical’ (encryption and decryption keys are different). Accordingly, the password of 48 bits is further translated into a first encryption key of 128 bits by adding 80 additional bits of key length in accordance with a predetermined scientific discipline, and stored in a non-volatile memory  21  at step S 31  of  FIG. 5 . Each of the key is generated at the 128-bit standard in this embodiment, while the 64-bit, 196-bit, or 256-bit key is acceptable to implement the data access method. Prior to transmitting the data to be encrypted through the interface  20  from the data read/write device to a flash memory  22 , the encryption unit  23  adopts a given encryption algorithm, e.g., AES of 128 bits, along with the first encryption key in the non-volatile memory  21 , and then transforms the data in plaintext to a scrambled ciphertext, i.e., an encrypted data, as illustrated in step S 32  of  FIG. 5 . In addition to AES, the data can be encrypted according to Rivest-Shamir-Adleman (RSA), Data Encryption Standard (DES), and Triple-DES. 
         [0041]    As discussed above, steps S 30  to S 32  are operations of encrypting, while operations of decrypting begin with S 33  of  FIG. 5 . To regulate access to the data, re-enter of the password is required to decrypt the encrypted data stored in the flash memory  22 . After requesting access to the data at step S 33 , a checkbox prompts for re-entering of password on the read/write device, as shown at step S 34  of  FIG. 5 . The data in its encrypted form which is unintelligible to unauthorized intruders, is released responsively. To decrypt the encrypted data and enable readout of the decrypted data through the interface  20  outbound to the data read/write device, a decryption key corresponding to the first encryption key is required. Steps S 35  to S 36  are to illustrate the translation of the re-entered password into a second encryption key for decoding the header  221 . In the header  221 , there is an 8-byte field in the BPB of the first logical block (LBA 0 ), employed to identify the file system type, i.e. FAT in this embodiment. After the decoding, the header  221 , also known as the first logical block, is examined to locate a string of “FAT” at the first 3 bytes at steps S 37  and S 38 . If a mapping between the first encryption key and the re-entered password is defined, the 8-byte field in the BPB of the first logical block is successfully translated, and a string of “FAT” is located in the first 3 bytes of the filed at step S 38 . 
         [0042]    Otherwise, step S 38  would return to step S 34  if a string of “FAT” is not successfully translated and located, and a checkbox prompts for password again on the read/write device if no mapping is defined. As a string of “FAT” is located in the BPB field of the header  221 , a particular level of security clearance is granted. Therefore, the data access request of step S 33  is allowed, and the decryption key is retrieved to decrypt the encrypted data at the decryption unit  24 . Resultantly, the data is restored to its original plain text, and unfolded to the read/write device through the interface  20 , as shown in step S 39  of  FIG. 5 . Even the flash memory  22  is compromised, or dismantled from the storage apparatus  1  to assemble with another storage apparatus, the encrypted data remains ciphered without the correct decryption key. 
         [0043]    Certainly, the encryption and the decryption operations discussed above can be accomplished either by software or hardware implementation. In alternate embodiments, the password can be predeterminedly created on manufacturers&#39; site, and users can revise the password on the read/write device. The properties of the present invention make it especially well-suited to applications of a USB PenDrive, a SD card, a MMC, a CF card, and a USB flash drive. Besides, the header of the flash memory bearing information about how the data is processed, is preferably partitioned in the FAT format. 
         [0044]    In conclusion, the present invention discloses a data access method for applications in data storage apparatus, to ensure confidential information from falling into wrong hands, in particular the industrial espionage among highly competitive businesses. Differentiated from the prior art, the data in encrypted form is released at the first place before the password is verified, even though an incorrect password is entered. The present invention further utilizes the file-system-dependent information recorded in the header, i.e. the first logical block, to escalate the protection and integrity of the data. Besides, the password can be further translated into an encryption key with a key length of 64-bit, 128-bit, 196-bit, or 256-bit key. If the password is verified incorrect or invalid, it suggests that no mapping be defined. Accordingly, the data remains in encrypted state, which is unintelligible to unauthorized persons, to prevent leakage of the data brought about by compromise of the encryption key after a significant amount of calculation and many times of “trial-and error” for the possible key. Only when the entered password conforms to the encryption key based on the information of the header, the encrypted data can be decrypted successfully in decipherable text. The present invention ensures that transitory data stored in a memory remains confidential, and eliminates the prior potential security holes by prohibiting malicious key-loggers from deciphering the key, thereby dramatically enhancing overall security of digital contents. 
         [0045]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.