Abstract: This article introduced one kind design and realizes based on DVD-ROM the application content jamming system (CSS). This system may prevent effectively to the DVD disk sheet illegal copy. In the article through to its principle of work and practical application’s analysis, gives it to realize the plan finally, and uses Verilog the HDL complete overall system’s design. The function simulation and the FPGA confirmation indicated that designs successfully.
Key word: Content Canada harasses the system; DVD; Verilog HDL; FPGA confirmation
Directing Word
The DVD-ROM video frequency and the voice data are undergo the encryption code, Canada harasses the source is the title key (Tittle Key), simultaneously the title key (compact disc key) encrypts by the compact disc key, the main engine in broadcasts video disk’s time must attain these two keys to be able to broadcast smoothly. In the key transmits from the DVD driver to main engine’s process, to guarantee that data-transmission channel’s security, namely the guarantee compact disc key and the title key can transmit safely, CSS has established an authentication mechanism (Authentication Mechanism), carries on Canada through main line key (BUSKEY) to the compact disc key and the title key to harass. Because can prevent effectively to the DVD compact disc’s illegal copy, CSS is used nearly by all commercial DVD equipment.
When DVD broadcast machine read data, in servo-control chip’s CSS will carry on the complex cryptographic check. If cryptographic check successfully, the data only then may the reduction MPEG-2 form and transforms into the video signal and the tonic train signaling. This article introduced one kind the CSS design which completes the authentication process, the compact disc key and title key’s Canada harasses and transmits, it uses in the DVD servo-control chip.
CSS principle and system analysis
According to the DVD standard as well as the CSS related standard, CSS mainly contains two parts:
between (1)DVD driver and main engine’s authorized authentication.
Its authentication flow is: The main engine transmits a stochastic symbol stream to arrive at the driver, the driver after its encryption returns to the main engine, after the main engine decipher, confirmed whether and the original symbol stream is the same, if same, then the driver is authorized. Main engine’s authorized process and driver’s authorized process is the same. The interactive authorization’s result is produces the main line key to use to the data which transmits between the main engine and the driver carries on the encryption. Only the main engine and the driver may produce the key which uses in deciphering.
(2) compact disc key and title key’s Canada harasses. Canada harasses the process is:
①The driver harasses with the main line key to the compact disc key and title key Canada. CSS harasses to key’s Canada starts contains the compact disc key and the title key’s sector data in the servo-control chip from the DVD compact disc read. The data reads in UPI (microprocessor connection) the register then to transmit first to the memory block administration module (BM-Buffer Manager) and produces the CSS memory indicator to use in the CSS read data. CSS one time reads a byte from BM the key, after Canada harasses, stores up to BM in the region which aims by the microprocessor memory indicator. After key Canada harasses completes, CSS sends out CSS the DONE interrupt.
②Through the microprocessor memory indicator, after the UPI register reads Canada harasses the key and transmits to the main engine.
③After the main engine receives Canada harasses the compact disc key and the title key with it carries on the solution to harass. Uses the correct compact disc key and the title key main engine may to compact disc’s audio frequency, the video data solution harass. 
Figure 1 CSS structure drawing
The CSS system structure and the main module hardware realize
Figure 1 expressed that the CSS system structure drawing, it is composed of four modules:
① CSS_PROC: Processes the CSS data feeds output, it is CSS and in the DVD servo-control chip BM and the UPI connection;
② CSS_RAND_GEN: Had the 80-bit pseudo-random numbers to use in the DVD driver to main engine’s authentication, the pseudo-random numbers production uses 42 linear feedback shift register (LFSR-LinearFeedback Shift Register);
③ In CSS_AUTH:CSS most essential authentication operation module;
④CSS_SM: Controls the CSS_AUTH module the authentication process, and opens the key transmission in CSS_PROC.
Realizes between the DVD driver and main engine’s interactive authorized authentication as well as the compact disc key and title key’s Canada by above these module constitution’s CSS system harasses two big functions, the system clock is 100MHZ.
Data path design
The CSS most essential place lies between the main engine and the DVD driver’s authentication, thus authentication operation module CSS_AUTH becomes the design key. According to Figure 1 authentication process, it completes by 5 submodules, as shown in Figure 2: 
Figure 2 CSS_AUTH structure drawing
In Figure 2, DRV_AUTH obtains the driver to main engine’s response value DRV_RES, returns completes the main engine to the main engine and produces the main line key to driver’s authentication, but DEC_AUTH together completes the driver with KEY_SHARE to main engine’s authentication; DEC_AUTH recaption main engine after driver’s response value, through obtains a reference value with the main engine opposite process, after it and DEC_RES comparison, confirms the main engine, confirms has the connection number successfully, gives KEY_SHARE to produce finally with the main line key which encrypts. In order to cause CSS_AUTH the area to be most superior, as shown in Figure 2, CSS_DRV_AUTH, CSS_DEC_AUTH and in the CSS_KEY_SHARE three modules contains the logical gate to extract together forms independent module CSS_AUTH_COMMON, simultaneously designs multi-channel choice module AUTH_MUX_COMMON to choose AUTH_COMMON the data pool. This kind of module multiplexing structures very good have saved the electric circuit area, raised the operating speed.
When these modules, the superposition uses module AUTH_COMMON which is containing the most complex data way, the design the division is four sub-modules, as shown in Figure 3: 
Figure 3 AUTH_COMMON structure drawing
In Figure 3, in the KEY module deposits AK which obtains through L ICENSE, through the XOR module and PCD[79:40] (regarding DRV_AUTH) PCD is the 80bit stochastic symbol stream which transmits from the main engine; Is driver oneself produces regarding DEC_AUTH PCD with by carries on the authentication to the main engine the 80_bit random number; But regarding KEY_SHARE PCD is the DEC_AUTH module operation result, namely the driver the zonula adherens number which produces to the main engine authentication process) carries on different or, then after the SCHEDULER module (by two LFSR, a full adder and some XOR gate and register is composed) obtains IAK, finally delivers SUBSTITU the TOR module to obtain the AUTH three sub-module respective operation result.
In the design the most difficult part lies in SUBSTITUTOR the design, its hardware architecture as shown in Figure 4, by 30 SBOX, 10 TBOX and a series of XOR gates is composed. It is harasses the algorithm based on the CSS Canada, uses the 5X6 operation array to realize. The entire operation carries on according to the row, namely starts in the 0th row from the 0th line to calculate first to the 4th line, then starts in the 1st row from the 0th line to calculate to the 4th line, like this has operated to the 5th row. When operation the SBOX ranks address chooses by the special control circuit. 
Figure 4 SUBSTITUTOR hardware structure drawing
And, T represents T_BOX, only in the 5X6 structure’s 34th row appearance, mainly carries on the XOR operation and the corresponding setting to the data-in; SBOX hardware architecture as shown in Figure 5: 
Figure 5 SBOX hardware structure drawing
And, PRE_TABLE and POST_TABLE are search the table, realizes with 8X8ROM, like this completes the entire authentication process to need 32 such ROM. From the chart may see that the ROM address decided by the data-, after site search namely obtains the output result. The search table and AK must apply for the permit equally to the DVD association to be able to obtain the concrete data.
State machine design
According to the system analysis, CSS has 6 kind of working patterns, respectively is:
①Calculates DVD driver’s response value DRV_RES;
②Produces uses to main engine authentication call DEC_CHAL to main engine’s authentication;
③Produces main engine’s reference value DEC_REF, and does with main engine’s response value DEC_RES compares, if same, then the main engine authenticates and has the connection number through the DVD driver;
④Produces the main line key:
⑤Carries on Canada with the main line key to the compact disc key to harass;
⑥Carries on Canada with the main line key to the title key to harass. 
Figure 6 phase transition chart
In CSS uses the MOORE type the state machine, carries on the phase transition regarding these working pattern. Its phase transition chart as shown in Figure 6.
Function simulation and FPGA confirmation
According to the above design concept, carries on the RTL description with Verilog HDL to CSS. Uses Synopsys VCS to carry on the simulation for its 6 kind of patterns, through the Debussy PLI connection production profile document (.fsdb), carries on the analysis in Debussy to the profile. The compact disc key altogether has 2048 bytes, in the DVD sector contains the compact disc key’s data area in the 13th to 2060 bytes. In tests in the script to establish the main line key’s value in advance and to induct 2352 bytes the DVD sector data to BM in order to carry on the function testing to CSS. Only aims at compact disc key Canada in here to harass the pattern the simulation profile to carry on the explanation.
And, CSS_BM_RD_REQ_CNT is CSS sends out to BM reads the request signal, DISC_KEY_XFER_EN is the compact disc key transmission enables the signal, is the high level is effective. BM_CSS_DATA[7:0] is the compact disc key data, saves in BM FIFO. When above two enable the signal is “1″, the compact disc key from the BM transmission to CSS, each clock cycle transmits a byte. TOTAL_OFFSET_CNT is the data total byte displacement quantity which transmits from BM, when TOTAL_OFFSET_CNT=11 the DISC_KEY_STARTLOC setting, symbolizes that starts Canada to harass the compact disc key. Transmits a byte data every time the compact disc key, uses the main line key to carry on the “or else” to it, and the result which Canada will harass in the next clock cycle sends out and has the data to symbolize effectively. Analyzes CSS_BM_DATA_OUT[7:0] to be possible to know, the main line key carried on correct Canada to the compact disc key to harass and to transmit.
In order to guarantee that the CSS system design the accuracy, we select Xilinx Spartan2 the XC2S50 component to make the FPGA confirmation. We produce the net table document in Synplify (.edf), then (.v) and the line time delay document (.sdf) uses in VCS carries on the simulation after the XilinxISE production element mesh table document, finally produces FPGA downloading document (bit). The XC2S50 hardware takes situation as shown in Table 1: 
Table 1 FPGA resources distribution list
Concluding remark
This article introduced one kind of content jamming system (CSS) design and realizes. After having analyzed its principle of work and the system structure we have given the data path and state machine’s design method, explained with emphasis SUBSTITU TOR design, this is in the overall system design difficulty. This system’s indicated in DVD servo-control electric circuit application that it had guaranteed the DVD driver to main engine’s compact disc data-transmission channel’s security, may prevent effectively to the DVD disk sheet illegal copy, has achieved the design requirements.
