Abstract:
A disk anti-copy system. An encrypted anti-copy mechanism with a device key table (Kd Table) prepared in a device and a fixed encryption processed media key block (MKB) pre-recorded in a disk is established. Only through the appropriate fixed encryption process between the key and the MKB can the device correctly read the disk. This controls the device and prevents disks from being copied. Moreover, the invention provides a method and device for preventing disks from being copied.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The invention relates to a key management system and, in particular, to a disk anti-copy system used between a digital device and a digital recording medium that uses a device key table (Kd Table) prepared in the device and a media key block (MKB) pre-recorded in the disk to perform fixed encryption and decryption processes.  
           [0003]    2. Related Art  
           [0004]    With the tremendous progress in computer hardware and software technologies and the wide multimedia applications, the technology of digital data storage has received a lot of attention. However, since the digital data can be readily dupliciated, the digital data protection stored on the recording medium is not as easy as traditional publications. The related intelligence property (IP) problems become serious. To protect the privacy and security of digital data, many anti-copy systems have been proposed.  
           [0005]    According to the employed techniques, the normal anti-copy system can be divided into two parts: cipher algorithm and key management. Most of the prior art focuses on the improvement in the cipher algorithm. Very few people devote themselves to the new development in key management. However, anti-copy systems that involve only improvements in the cipher algorithms are very vulnerable. Therefore, it is imperative to establish a robust and complete key management mechanism, through which digital data storage security and privacy can be truly guaranteed.  
           [0006]    The CPPM (Content Protection for Pre-recorded Media) and CPRM (Content Protection for Recorded Media) are two anti-copy system standards used in read-only recording media and rewriteable recording media. Both methods utilize the new generation technology in the cipher algorithm and key management. The main operation mode is to embed a device key table (Kd Table) into the device during manufacturing and then along with a media key block (MKB) pre-recorded in a recording medium, thus hoping to prevent the disks from being copied. The general idea is shown in FIG. 3. Nevertheless, both methods have the keymeet-in-the-middle problem. Eventually, it can be broken by hackers.  
           [0007]    Therefore, it is of great importance for the digital data storage technology to provide an ideal key management system that makes necessary improvements in existing Kd Table and MKB. The objectives are to lower the decipher probability as well as to increase the confidentiality and security of the recorded data contents.  
         SUMMARY OF THE INVENTION  
         [0008]    In view of the foregoing, the invention provides a disk anti-copy system, method and the corresponding device. The invention achieves the goals of lowering the decipher probability and increasing the disk privacy and security using improved device key table (Kd Table) and a media key block (MKB) in the disk (recording medium).  
           [0009]    Another objective of the invention is to increase the robustness of the disk anti-copy mechanism and the flexibility in use. The maintenance and management of the Kd Table in the device and the MKB in the recording medium are achieved through a centralized management of a key management system. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:  
         [0011]    [0011]FIG. 1 shows the structure of the disclosed anti-copy system;  
         [0012]    [0012]FIG. 2 is a flowchart of the disclosed anti-copy method;  
         [0013]    [0013]FIG. 3 shows the disk anti-copy technique in the prior art;  
         [0014]    [0014]FIG. 4 shows the disk anti-copy concept of the invention;  
         [0015]    [0015]FIG. 5 a  is a schematic view of the data structure in the Kd Table;  
         [0016]    [0016]FIG. 5 b  is a schematic view of the media key block type 1 (MKB 1); and  
         [0017]    [0017]FIG. 5 c  is a schematic view of the media key block type 2 (MKB2). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    The specification discloses a disk anti-copy system, method and the corresponding device. By disk, we generally refer to the so-called “recording medium.” The basic types of the recording media include “read-only” and “re-writeable.” The device  50  mentioned above includes in general the software and hardware that can read/write on a disk (recording medium)  100 . Examples are audio/video (AV) players and CD-ROM players.  
         [0019]    First, we use FIG. 1 to explain the disclosed disk anti-copy system. The system basically covers a cipher algorithm and a key management system. However, the cipher algorithm part is not the essence of the invention and can be understood from the related prior art. Therefore, we will emphasize on the key management system  200 . The main function of the key management system  200  is the encryption anti-copy process by preparing a device key table (Kd Table) in the device  50  and pre-recording a media key block (MKB) in the disk  100 .  
         [0020]    The concept of the key management system  200  is schematically shown in FIG. 4. It contains the following modules.  
         [0021]    (1) Storage database  210 . It stores several Kd Tables (see FIG. 5 a ), each of which corresponds to a device  50 .  
         [0022]    (2) MKB Type 1 (MKB 1) Generating Module  220 . It determines an upper limit, Smax, of the MKB1 according to the number of device keys (Kd&#39;s) in the Kd Table and fills in the field of the MKB1 a random number series, Dt1, produced by an operation module  240 , generating the MKB1 (see FIG. 5 b ).  
         [0023]    (3) MKB Type 2 (MKB2) Generating Module  230 . It performs decipher operations for each random number series corresponding to each special value, Svalue, for all the Kd&#39;s in the Kd Table. The result undergoes a logic operation (the XOR operation) with the number 0, generating a temporary key series, Ktemp. The temporary key series undergoes the same logic operation with a media key, Kmedia, as before, producing a new temporary key series result. An additional device key, Kaddition, performs an encryption operation on Ktemp to produce an encrypted series, Dt2. The encrypted series is then stored in the field of additioanl special value, Saddition, in the MKB2. The module  230  completes the process of filling the data into the MKB2 for a single device  50 . Such a process is repeated for each of the devices  50  and, finally, the MKB2 is produced (see FIG. 5 c ).  
         [0024]    (4) Operating Module  240 . It is used to generate a random number series. It further performs logic operations, encryption algorithm operations, and decryption algorithm operations. The cipher algorithm used by the module  240  may be conventional. However, it is preferred to use the new-generation Rijdael cipher standards.  
         [0025]    (5) Recording Module  250 . It pre-records the Kd Table of each device to the corresponding device  50 . It also pre-records the MKB Type 1 and the MKB Type 2 to the disk  100 . In particular, the pre-recording location is in the lean-in area of the disk.  
         [0026]    In the following paragraph, we use FIG. 2 to explain the decryption anti-copy process on the device  50  and the disk  100  according to the invention.  
         [0027]    First, the device  50  reads from the disk  100  the MKB1, the MKB2, and the Kd Table corresponding to the device  50  (step  300 ). The device  50  further reads several device keys (Kd&#39;s) from the Kd Table, several special values, Svalue, corresponding to the Kd&#39;s, and several random number serieses, Dt1, corresponding to the special values from the MKB1 (step  310 ). Afterwards, the decryption results of the random number serieses using the device keys are computed and undergo a logic operation (the XOR operation), producing a temporary key series, Ktemp (step  320 ). The additional device keys, Kaddition, and the corresponding additional special values, Saddition, in the Kd Table are read out. The additional special values are then used to extract the corresponding encryption number series, Dt2, in the MKB2 (step  330 ). Operations are then performed to obtain encryption results of the encryption serieses using the additional device keys. The encryption results undergo a logic operation with the temporary key series, generating the final media key (Kmedia). The media key is then used to read the contents in the disk  100 .  
         [0028]    In fact, the operation of the invention can be further explained through mathematical equations. Suppose there are m devices  50 , each of which has a device key table with n keys. For the ith device  50 , the anti-copy process performed on the device  50  and the disk  100  by the disclosed key management system  200  is as follows:  
         [0029]    (1) Set Ktemp 0;  
         [0030]    (2) Ktemp=Ktemp⊕D(Ki,Dt1_Si), for i=0,1 . . . ,n−1;  
         [0031]    (3) Set Ktemp=Ktemp⊕(Kmedia and obtain Dt2=E(Kaddition,Ktemp); and  
         [0032]    (4) Fill Dt2 into the Saddition&#39;th position.  
         [0033]    This completes the anti-copy encryption process for the ith device  50 . Repeating the above steps (1) through (4) m times can complete the process for the whole MKB2.  
         [0034]    In a similar fashion, when the ith device  50  reads the disk  100  and performs the decryption process as shown in FIG. 2, the details can be expressed as follows:  
         [0035]    (1) Set Ktemp=0;  
         [0036]    (2) Ktemp=Ktemp⊕D(Ki,Dt1_Si), for i=0,1 . . . n−1;  
         [0037]    (3) Read the Saddition&#39;th position in MKB2, i.e. Dt2_Saddition; and  
         [0038]    (4) Obtain Kmedia=Ktemp⊕E(Kaddition,Dt2_Saddition).  
         [0039]    Using the obtained Kmedia, the ith device  50  can read out the data stored in the disk.  
       EFFECTS OF THE INVENTION  
       [0040]    The disclosed disk anti-copy system, method and the corresponding device use improved device key table (Kd Table) and media key block (MKB) to perform the concept of level keys to make the encryption procedure more sophisticated. Due to the limited known conditions and many variables, the decipher probability can be greatly reduced, ensuring the privacy and security of the data stored in the disk.  
         [0041]    Moreover, the disclosed key management system can provide maintenance and management for the Kd Table of each device and the MKB of each recording medium. This makes the disk anti-copy mechanism more robust and flexible.