BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to an authentication method and related device used in a digital versatile disk (DVD) system, and more particularly, to a method and related device using several independent mapping relationships to simplify the encoding process during authentication.  
           [0003]    2. Description of the Prior Art  
           [0004]    Since the technology of digital versatile disks (DVDs) is developed, DVD shave become one of the most important storage media of information industry. The capacity and density of DVDs are far more than those of current compact disks (CDs). They are capable of storing a large capacity of video and multi-media data, enriching lives of people, and furthermore, recording large quantities of information and knowledge for the basis of the development of technology.  
           [0005]    The data stored in DVDs can be read by DVD-Rom (read only memory) drives. To maintain the legitimacy of reading the DVD title, an authentication mechanism has been set in constituting the specification of the DVD system. Please refer to FIG. 1. FIG. 1 is a function block diagram of a disk-play platform  10  cooperating with a DVD drive  14  for playing a DVD. The disk-play platform  10  of a DVD system could be a personal computer (PC). a master controller  12  of the disk-play platform  10  could be a DVD data decoding circuit in hardware, or a DVD playing software performed by the disk-play platform  10 . The disk-play platform  10  controls the DVD drive  14  to read the data of the DVD. For avoiding the illegal use of the DVD, the master controller  12  will confirm the legality of the DVD drive  14 . The authentication mechanism is as follows. The master controller  12  first sends an inquiring code  16  to the DVD drive  14 . Then the DVD drive  14  encodes the inquiring code  16  into an authentication code  18  according to a regulative encoding method and responds to the master controller  12  with the authentication code  18 . The master controller  12  checks the authentication code  18  given by the DVD drive  14  to determine whether the DVD drive  14  is legal. When the DVD drive  14  passes in authentication, it sends another inquiring code to authenticate the master controller  12 . Then the master controller  12  performs a procedure shown in FIG. 2 to generate a corresponding authentication code according to the inquiring code sent by the DVD drive  14  and sends back to the DVD drive  14  so as to authenticate that the master controller  12  is also legal . After the above-mentioned mutual authentication process, the DVD drive  14  further reads the authenticated data of the DVD for authenticating the master controller  12  (the DVD drive  14  sends another inquiring code and checks the corresponding authentication code generated and sent back by the master controller  12 ). Only DVD systems that pass the above-mentioned authentication are capable of reading the data of DVDs correctly.  
           [0006]    Please refer to FIG. 2. FIG. 2 is a schematic diagram of the procedure of the DVD drive  14  generating the authentication code  18  corresponding to the inquiring code  16 . According to the specification of DVD system, the inquiring code  16  generated by the master controller  12  is encoded by a pre-procedure  22 . Then the encoded result from the pre-procedure  22  is further mapped to another code according to a pre-table  24 . After another encoding by a mid-procedure  26 , the encoded result is again mapped to another code according to a post-table  28 . Finally, the authentication code  18  is generated by a post-procedure  30 . The pre-procedure  22 , the mid-procedure  26 , and the post-procedure  30  are defined in the specification of the DVD system, and the detailed information is well known in the industry field. For brevity, further details are omitted here. Please refer to FIG. 3 and FIG. 4 for showing the mapping of the pre-table  24  and the post-table  28 .  
           [0007]    [0007]FIG. 3 and FIG. 4 respectively show the table look-up relationship set up by the pre-table  24  and the post-table  28 . The inquiring code  16  is eight bits when inputted into the pre-table  24  and the post-table  30 . The mapping result from the pre-table  24  and the post-table  30  are also 8 bits. For convenience, all numbers shown in FIG. 3 and FIG. 4 are hexadecimal (In other words, the numbers of  0 ,  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 , A, B, C, D, E, F shown in FIG. 3 and FIG. 4 respectively represent the decimal numbers of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15). The most significant bit (MSB) is used as the 7 th  bit, and the least significant bit (LSB) is used as 0 th  bit. The row  24 A shown in FIG. 3 includes sixteen kinds of combinations of the 7 th  bit to the 4 th  bit of the inquiring code inputted into the table  24 , and the column  24 B shown in FIG. 3 includes sixteen kinds of combinations of the 3 rd  bit to the 0 th  bit of the inquiring code inputted into the table  24 . A numeral composed of two hexadecimal numbers at a junction of the row  24 B and the column  24 A represent the output according to the pre-table  24 . For example, if an inquiring code inputted into the pre-table  24  is 00 (hexadecimal), then the inquiring code is mapped to 4C (hexadecimal) according to the pre-table  24  shown in FIG. 3. As well, if the inputted inquiring code is 9A, then the pre-table  24  outputs  5 A. Based on the same principle, the row  28 A shown in FIG. 4 includes sixteen kinds of combinations of the 7 th  bit to the 4 th  bit of the input of the post-table  28 , and the column  28 B includes sixteen kinds of combinations of the 3rd bit to the 0 th  bit of the input of the post-table  28 . An output, which is composed of two hexadecimal numbers, of the post-table  28  is at a junction of the row  28 A and the column  28 B. For example, if an input inquiring code is 31 (hexadecimal), then the inquiring code is mapped to 64 (hexadecimal) as an output according to the post-table  28  shown in FIG. 4. As well, if the inputted inquiring code is 8E (hexadecimal), then the inquiring code is mapped to 1F (hexadecimal) according to the post-table  28 .  
           [0008]    In the prior DVD drives, the pre-table  24  and the post-table  28  shown in FIG. 3 and FIG. 4 are directly implemented by a logic circuit. In other words, a designed logic circuit composed of many logic gates is formed to implement table look-up relationships set by the above-mentioned two tables. An inquiring code in the form of digital signal is inputted into the logic circuit. After the operation of the logic circuit, the inquiring code is mapped to an output in the form of a digital signal according to the pre-table (or post-table). However, the larger and more complex the table, the more logic gates are required. As shown in FIG. 3 and FIG. 4, the pre-table  24  and the post-table  28  defined in the specification of the DVD system are used to deal with all 256 kinds of combinations of an eight-bit input mapped to an eight-bit output. In the prior art, the pre-table  24  and the post-table  28  shown in FIG. 3 and FIG. 4 are directly implemented by a logic circuit, and therefore, the logic circuit is completed and the gate count is great. For containing a large number of logic gates and a complex layout, the logic circuit used to implement the pre-table and the post-table occupies some layout area and also consumes great power, which results in bad effects on the integration and the energy efficiency of DVD drive circuits. In addition, every logic gate brings a specified gate delay, so the more logic circuits used, the lower the operating efficiency of the logic circuit is. Furthermore, for ensuring normal operation of the logic circuit used for implementing the pre-table and the post-table, the logic circuit must be tested during manufacturing processes. The prior art directly calculates 256 kinds of combinations included in the pre-table and the post-table. Therefore, all 256 kinds of combinations must be tested during manufacturing processes, which wastes time and increases the production cost.  
         SUMMARY OF INVENTION  
         [0009]    It is therefore a primary objective of the claimed invention to provide a method and related device for substantially simplifying the performance of the pre-table and the post-table to solve the above-mentioned problem. The pre-table and post-table used in the DVD authentication process respectively map an 8-bit code to another 8-bit code. That is, 256 mapping relations should be implemented to realize each of the pre-table and the post-table. Particularly, the hardware designed to realize the 256 mapping relations for each of the two tables becomes complex, and needs more area for practical circuit layout.  
           [0010]    The claimed invention discloses a novel method to simplify the realization of the pre-table and post-table. Each table is realized by two sub-tables. The original 8-bit code used in authentication is separated into two portions of 4-bits each. In addition, each of the sub-tables maps the 4-bit portion to another 4-bit output code using only 16 mapping relations. Then the 4-bit output codes of the two sub-tables that are used to realize the pre-table or the post-table are combined to obtain a result 8-bit code. The mapping relationship between the original 8-bit code and the result 8-bit code meets that defined by the pre-table or the post table. In other words, the original pre-table or the post-table with 256 mapping relations can be realized by only 32 mapping relations (16 mapping relations for each sub-table) according to the disclosed method.  
           [0011]    It is therefore a primary objective of the claimed invention to provide a method for substantially simplifying the realization of the pre-table and the post-table. Also, according to the disclosed method, the hardware circuit for realizing the pre-table and post-table can be implemented using fewer logic gates so as to lower cost and time for designing, manufacturing and verifying such circuit. Also, the layout area and power dissipation can be reduced. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic diagram of a DVD drive used in a disk-play platform.  
         [0013]    [0013]FIG. 2 is a schematic diagram of an authentication process of a DVD drive.  
         [0014]    [0014]FIG. 3 is a schematic diagram of a pre-table shown in FIG. 2.  
         [0015]    [0015]FIG. 4 is a schematic diagram of a post-table shown in FIG. 2.  
         [0016]    [0016]FIG. 5A and FIG. 5B respectively indicate two sub-tables used for calculating the pre-table shown in FIG. 3 according to the present invention.  
         [0017]    [0017]FIG. 6A and FIG. 6B respectively indicate two sub-tables used for calculating the post-table shown in FIG. 4 according to the present invention.  
         [0018]    [0018]FIG. 7A and FIG. 7B are schematic diagrams of logic circuits used for calculating the two sub-tables shown in FIG. 5A and FIG. 5B, respectively.  
         [0019]    [0019]FIG. 8A and FIG. 8B are schematic diagrams of logic circuits used for calculating the two sub-tables shown in FIG. 6A and FIG. 6B, respectively. 
     
    
     DETAILED DESCRIPTION  
       [0020]    In the present invention, pre-table and post-table defined in the specification of the DVD system are implemented by independent sub-tables. In the prior method, an 8-bit input is directly mapped to an 8-bit output according to the table look-up relationships. In the present invention, a specified method is used to divide the 8-bit input code into a first 4-bit portion and a second 4-bit portion. The first portion and the second portion respectively form a first 4-bit sub-output code and a second 4-bit sub-output codeaccording a table look-up relationship set up by a sub-table. Consequently, an 8-bit output code is formed by combining the first sub-output code and the second suboutput code. The relationship between the output code and the original input code conforms to the pre-table or the post-table defined in the specification of the DVD system.  
         [0021]    Please refer to FIG. 5A and FIG. 5B. FIG. 5A and FIG. 5B respectively indicate the two sub-tables used for implementing the pre-table according to the present invention.All numbers shown in FIG. 5A and FIG. 5B are hexadecimal numbers. To implementthe pre-table, in which an 8-bit input is mapped to an 8-bit output, the input code is first divided into a first 4-bit portion and a second 4-bit portion. The most significant bit (MSB) is used as the 7 th  bit, and the least significant bit (LSB) is used as 0 th  bit. The first portion is composed of the 3 rd  bit to the 0 th  bit of the input code, and the second portion is composed of the 7 th  bit to the 4 th  bit of the input code. The first sub-output code corresponding to the first portion is composed of the 3 rd  bit to the 0 th  bit of the 8-bit output code, and the second sub-output code corresponding to the second portion is composed of the 7 th  bit to the 4 th  bit of the output code. The row  30 A shown in FIG. 5A includes all sixteen kinds of combinations of the first portion containing four bits. The sub-table shown in FIG. 5A indicates table look-up relationships in which the first portion is mapped to the first sub-output code. For example, if the first portion of the input code is 0 (hexadecimal), then the corresponding first sub-output code is C (hexadecimal); if the first portion is 5 (hexadecimal), then the corresponding first sub-output code is D (hexadecimal), and so on. As well, the second portion of the input code is mapped to a second sub-output code according to the sub-table shown in FIG. 5B. The row  30 B shown in FIG. 5B includes all sixteen kinds of combinations of the second portion containing four bits. According to the FIG. 5B, if the second portion of the input code is 0 (hexadecimal), then the corresponding second sub-output code is 4 (hexadecimal); if the second portion is 7 (hexadecimal), then the corresponding second sub-output code is F (hexadecimal), and so on.  
         [0022]    The processes of the present invention using the sub-tables shown in FIG. 5A and FIG. 5B for calculating the pre-table are described as follows. For example, an input code “9A” (eight bits, hexadecimal) is first divided into a first portion composed of “A” and a second portion composed of “9” for obtaining an output code according to the pre-table. According to the sub-table shown in FIG. 5A, a first sub-output code is “A”. As well, the second portion composed of “9 is mapped to a second sub-output code “5” according to the sub-table shown in FIG. 5B. Combining the second sub-output code with the first sub-output code forms the output code “5A”. The output code conforms to the table look-up relationship set up bythe pre-table shown in FIG. 3 (the input code “9A” is mapped to the output “5A” according to the pre-table shown in FIG. 3). For another example, if an input code is “00”, then the both first portion and the second portion is “0”. According to FIG. 5A and FIG. 5B, the first and the second sub-output codes are respectively “C and “4”. Combining the second sub-output code with the first sub-output code forms the output code “4C”. The output code conforms to table look-up relationships defined bythe pre-table shown in FIG. 3 (the input code “00” is mapped to the output “4C” according to the pre-table shown in FIG. 3).  
         [0023]    Based on the above-mentioned principle, the present invention also uses two sub-tables for implementing the post-table shown in FIG. 4. Please refer to FIG. 6A and FIG. 6B. FIG. 6A and FIG. 6B respectively indicate the two sub-tables used for implementing the post-table shown in FIG. 4 according to the present invention, and all the numbers shown in FIG. 6A and FIG. 6B are hexadecimal numbers. Different from the above-mentioned method of implementing the pre-table, now the first 4-bit portion is composed of the 7 th , 6 th , 3 rd , and 2 nd  bit of the 8-bit input code, and the second 4-bit portion is composed of the 5 th , 4 th , 1 st  and 0 th  bit of the input code. The first sub-output code corresponding to the first portion of the input code is the 3 rd  bit to the 0 th  bit of the 8-bit output code, and the second sub-output code is composed of the 7 th  bit to the 4 th  bit of the output code. Similar to FIG. 5A and FIG. 5B, the row  32 A shown in FIG. 6A includes all sixteen kinds of combinations of the first portion, and the first portion is mapped to the first sub-output code according to the sub-table shown in FIG. 6A. As well, the row  32 B shown in FIG. 6B includes all sixteen kinds of combinations of the second portion of the input code, and the second portion is mapped to the second sub-output code according to the sub-table shown in FIG. 6B.  
         [0024]    An example for illustrating the processes of the present invention implementing the post-table shown in FIG. 4 is described as follows. An 8-bit input code is “31” (hexadecimal), which is also represented as “00110001” (arranged from the 7 th  bit to the 0 th  bit) in binary. Taking the 7 th , 6 th , 3 rd  and 2 nd  bit of the input code as a first portion, so the first portion is composed of “0000” in binary and is also represented as a hexadecimal number of “0”. As well, taking the 5 th , 4 th , 1 st  and 0 th  bit of the input code as a second portion, so the second portion is composed of “1101” in binary and is also represented as a hexadecimal number of “D”. According to the sub-table shown in FIG. 6A, the first portion “0” is mapped to the first sub-output code “4” (hexadecimal), and the second portion “D” is mapped to the second sub-output code “6” according to the sub-table shown in FIG. 6B. Combining the first sub-output code with the second sub-output code forms the complete 8-bit output code “64”, which conforms to the table look-up relationship defined bythe post-table shown in FIG. 4. For another example, an input code is hexadecimal numbers “8E”, which is also represented as “10001110” in binary. The first portion is composed of “1011” in binary (also represented as a hexadecimal number of “B”), and the second portion is composed of “0010” in binary (also represented as a hexadecimal number of “2”). According to the sub-tables shown in FIG. 6A and FIG. 6B respectively, the first sub-output code is “F” (hexadecimal) and the second sub-output code is “1” (hexadecimal). Combining the first sub-output code with the second sub-output code forms the complete output code “1F”, just as the input code “8E” mapped to the output code “1F” according to the post-table shown in FIG. 4. According to the above-mentioned description of the sub-tables in the present invention, one skilled person can easily prove that the two sub-tables disclosed by the present invention in the FIG. 5A and FIG. 5B completely implement all table look-up relationships defined by the pre-table shown in FIG. 3. As well, the sub-tables shown in FIG. 6A and FIG. 6B can completely implement all table look-up relationships defined by the post-table shown in FIG. 4.  
         [0025]    In conclusion, a specification of the DVD system defines a pre-tableand a post-table, as shown in FIG. 3 and FIG. 4, and an 8-bit input code is mapped to an 8-bit output code according to the pre-table and the post-table. In the prior method, each table shown in FIG. 3 and FIG. 4 comprises 256 kinds of table look-up relationships that are directly mapped. In the present invention, each of the pre-table and the post-table is implemented by combining two sub-tables. The two sub-tables shown in FIG. 5A and FIG. 5B are used to implement the pre-table with each sub-table only including sixteen kinds of the mapping relationships between an 4-bit input and an 4-bit output. As well, the two sub-tables shown in FIG. 6A and FIG. 6B are used to implement the post-table with each sub-table only including sixteen kinds of the mapping relationships between the 4-bit input and the 4-bit output . In contrast to the prior method, the present invention uses substantially simplified sub-tables to implement the completed pre-table and post-table.  
         [0026]    The advantage of the present invention is more obvious when in gate count to perform the technology of the present invention, because each of the sub-tables only includes sixteen mapping relationships between an input and an output. In contrast to the prior method that directly implements all 256 kinds of mapping relationships between an 8-bit input and an 8-bit output, the number of logic gates used for performing the present invention is substantially reduced and the energy consumedis also reduced. Furthermore, the integration of the logic circuit is substantially improved, so the layout area is reduced. In practice, the layout area used for completely implementing all mapping relationships defined by the pre-table and the post-table in the present invention is only one-ninth of the layout area used in the prior method. The logic circuit of the present invention has more operation efficiency because of shorter gate delays by less logic gates. In testing the logic circuit in the present invention, only sixteen kinds of combinations of each sub-table are necessary to be tested for ensuing a normal operation of the present invention (all four sub-tables used for implementing the pre-table and the post-table just have a total of sixty-four kinds of combinations that need to be tested). By contrast, the prior method directly calculates 256 kinds of mapping relationships defined by each of the pre-table and the post-table, so a total of 512 kinds of mapping relationships need to tested for ensuring a normal operation of the logic circuit. Therefore, the present invention can also decrease production costs of logic circuits.  
         [0027]    Please refer to FIG. 7A and FIG. 7B. In the above-mentioned description, the present invention uses the two sub-tables shown in FIG. 5A and FIG. 5B to completely implement all table look-up relationships defined by the pre-table shown in FIG. 3. FIG. 7A and FIG. 7B are schematic diagrams of logic circuits used for implementing the two sub-tables shown in FIG. 5A and FIG. 5B, respectively. The first encode unit  40  shown in FIG. 7A is used to implement the sub-table shown in FIG. 5A. Each sub-table of the present invention only includes sixteen mapping relationships between the input and the output, so the input of the first encode unit  40  is composed of four bits  42 A,  42 B,  42 C, and  42 D (as well as the first portion of the input code) and the output is composed of four bits  44 A,  44 B,  44 C, and  44 D (as well as the first sub-output code). The first encode unit  40  comprises a NOT gate I, an XOR gate Q, a multiplexer M, and a logic block  40 A. As well, the second encode unit  50  of FIG. 7B used to implement the sub-table shown in FIG. 5B also has an input composed of four bits  52 A,  52 B,  52 C, and  52 D (as well as the second portion of the input code) and an output composed of four bits  54 A,  54 B,  54 C, and  54 D (as well as the second sub-output code). The second encode unit  50  comprises a NAND gate N, a multiplexer M, and a logic block  50 A so as to implement the sixteen kinds of table look-up relationships shown in FIG. 5B.  
         [0028]    Please refer to FIG. 8A and FIG. 8B. The present invention uses the two sub-tables shown in FIG. 6A and FIG. 6B to completely implement all kinds of table look-up relationships defined by the post-table shown in FIG. 4, and the first encode unit  60  and the second encode unit  70  shown in FIG. 8A and FIG. 8B are used to implement the two sub-tables shown in FIG. 6A and FIG. 6B, respectively. The sub-table shown in FIG. 6A defines sixteen kinds of table look-up relationships between the 4-bit input (the first portion containing four bits) and the 4-bit output (the first sub-output code). Therefore, in the first encode unit  60 , four bits  62 A,  62 B,  62 C, and  62 D are defined as the input and four bits  64 A,  64 B,  64 C, and  64 D are defined as the output. The first encode unit  60  uses logic blocks  60 A,  60 B to implement sixteen kinds of table look-up relationships. In the second encode unit  70  shown in FIG. 8B, four bits  72 A,  72 B,  72 C, and  72 D are defined as the input (the second portion of the input code) and four bits  74 A,  74 B,  74 C, and  74 D are defined as the output (the second sub-output code). The second encode unit  70  uses logic blocks  70 A,  70 B to implement sixteen kinds of table look-up relationships defined by the sub-table shown in FIG. 6B. However, the logic circuits used to calculate each sub-table of the present invention may have many different kinds of equivalent designs, and the above-mentioned description is just one of embodiments.  
         [0029]    In a specification of the DVD system, the pre-table and the post-table, defined during authentication processes, comprise 256 kinds of table look-up relationships between the 8-bit input and the 8-bit output, respectively. In the above-mentioned description, the prior method directly uses logic circuits to calculate 256 kinds of table look-up relationships defined by each of the above-mentioned tables. Therefore, many logic gates and large layout areas are required. By contrast, the present invention discloses a method that uses two sub-tables to implement each of the pre-table and the post-table. Each sub-table only defines sixteen kinds of table look-up relationships between the 4-bit input and the 4-bit output, and 256 kinds of table look-up relationships defined by each of the pre-table and the post-table can be completely implemented through proper combination. Usingthe sub-tables disclosed by the present invention, one skilled person in designing logic circuits can easily use substantially simplified circuit designs to implement the pre-table and the post-table. Consequently, the disadvantages of the prior method, resulting in huge and complex logic circuits, can be improved. In the above-mentioned description, the DVD system performs authentication processes three times (a master controller authenticates a DVD drive, the DVD drive authenticates the master controller, and the DVD drive authenticates the master controller again), and the pre-table and the post-table are used each time in the authentication processes. Therefore, the present invention can be applied widely in each occurrence of the authentication processes.  
         [0030]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
A method and related device are used for a DVD (Digital Versatile Disk) system to authenticate the DVD system by generating an authentication code corresponding to an inquiring code. The inquiring code has a first portion and a second portion both having at least one bit. The method comprises: generating a first sub-authentication code according to only the first portion of the inquiring code, generating a second sub-authentication code according to only the second portion of the inquiring code, and combining the first sub-authentication code and the second sub-authentication code to form the authentication code.