Research Of Content Protection To Common Interface

Conditional Access which provides the necessary technologies for the operation of digital TV is widely used in the Pay-TV system. The implementation of the separation of STB and CAM greatly promotes the development of digital TV, however, when the plaintext which is descrambled by CA is transferred from CAM to STB, the program stream on the Common Interface is compromised to be illegally copied. To solve this problem, an Anti-copy mechanism is added between the STB and CAM, which is Content Control system.The work principle, implementation and separation of STB and CAM of DVB-CI standard is investigated, on this basis, CI Plus standard, the complementary standard of DVB-CI, is analysed, which determines the work principle, authentication mechanism and en/decryption of program content.The Random Number Generator module is designed for providing random number seeds for the operation of en/decryption in the chip of CAM. The RNG module is designed by full custom. In early period the RTL code design of RNG is accomplished, in the later period the simulation of RNG circuits is accomplished by VCS tool, which proves the function of RNG circuits is absolutely correct, then the synthesis of RNG circuits is accomplished by DC tool. When RNG is driven by the chip system clock, the delay of the critical path is 7.49 ns, the power dissipation is 3.88 mw. When RNG is driven by the internal clock of RNG, the delay of the critical path is 6.31 ns, the power dissipation is 4.27 mw. The number of the transistor of RNG is 19161. The design of RNG achieves the goal of higher speed, low power dissipation and small area.The random number generated by RNG is tested by using software tools, which pass through the FIPS140-2 standard, so the random number generated by RNG module has great randomness.