Research On Content Secure Protection Of Digital Video Broadcast

Digital video broadcast technology has been extensively used throughout the world, its main property is digital processing in program production, transmission, receiving and storage,which can bring colorful digital content and high quality audio/video to subscribers. Since the middle of 1990s, Digital Video broadcast technology has been developed and rised up.Over the world, it formed European DVB (Digital Video Broadcasting) standards, American ATSC (Advanced Television System Committee) standards, Japan's ISDB (Integrated Services Digital Broadcasting) Standard, which are three representative of Digital television technology system Standard. Among them, the DVB series Standard, facing the whole world, which is led by the ETSI (Euroupe Telecommunication Standard Institute), is most widely used. It covers processing and transmission, communication, etc. of multimedia information and is adopted by more than 100 countries. In China, digital TV standard is also based on the structure of DVB.However, owe to the use of production, transmission of full digitalization and storage of digital format, it makes the digital content more vulnerable to unauthorized copying and selling than the traditional analog content. Therefore, it is of great significance to protect the content of digital video broadcasting safely. There are two main kinds of current digital video content protection technology:one is a protection measure achieved through the network/transport layer of the the digital video transmission network,i.e.,also commonly called the digital TV scrambling/descrambling system or condition access system; Another is the protection technology in the application layer,i.e., the digital watermarking technology or DRM copyright protection technology which is widely used in the network video application nowadays. This paper mainly talks about the two kinds of safe content protection technology above and extends to progressive research.Firstly we analysis the framework and principle of the current digital TV conditional access system (CAS), points out that it is hard for the traditional three-level encryption conditional access system or the fixed group category four-level encryption to support the real-time authorization requirements of millions of digital TV users in the "three nets fusion" strategic background and development situation. According to the group key management, algorithm logic key hierarchical tree (LKH) algorithm,which is widely used in the communication network, it designs the complete subset cover and difference subset cover model, which is based on binary tree, and is combined with the fixed group. It can meet the requirements of binary tree constraint conditions:balance and full tree, flexibly support the smooth expanding of the users'scale. Research shows that, the authorized users send strategy, combining the subset cover based on LKH binary tree and fixed group, has greatly reduced the information of authorized users, saved the precious network bandwidth, accelerated thespeed of group authorizing, and maked it possible to support the quick authorizing for millions of users'scale in real time.In addition, through the safety analysis to encryption key transmission in the hierarchical encryption mechanism, it points out that the core of system safety is the safety the system main key MK in the CAS system, the traditional CAS MK in cured in SmartCard basically, once attacked, the card must be abolished. If we can update MK periodically or randomly, attackers makes no effect to attack MK, then the value and significance of attacking is los. It improves the practical significance in the security of the system furthermore. According to this, a multi-root key authorizing management algorithm is put forward, which is based on Shamir (t, n) threshold secret sharing. Research shows that the multi-root key authorizing management algorithm can implement the main key's online updating, and that Shamir (t, n) threshold secret sharing achieved discretization of the main key and improved the security of the main shared key through the randomization of multi-root shared key storage, so that it enhance the security of the system furthermore.Digital TV content providers hope to use content protection technology in order to protect their business profit and prevent digital content in the client from being illegally used and copied or being able to identify or track the content, digital watermarking algorithm played an important role in protecting the integrity of the digital content and copyright information, it is an effective weapon for safe content protection. The main technology of digital watermarking is divided into two kinds:the airspace (time domain) and the frequency domain, the traditional digital watermarking technology is based on unfolding in the airspace or the frequency domain. Scores Fourier transform is a combined time and frequency domain transform, The FRFT of the signal contains the airspace and frequency domain, which is very suitable for non-stationary signal processing, so it is a kind of excellent watermark transform algorithm. In FRFT basis, it constructed optimization chaotic sequence with long yards sequence, high degree of randomness, simpleness to achieve as spread spectrum sequence based on the chaos mapping algorithm, overcome the littleness of Gold code,low complexity,unbalance and so on in traditional code division multi-address system. Research shows that based on chaos sequence spread spectrum digital watermarking based on chaos sequence has excellent resistance to attack and safety.With the widely use of the digital video broadcast system throughout the world, HD video,4K video,3D video content also come to the stage, digital video content are increasing more rich, its value is more and more high, it will attract more research vision and power to carry on the effective security protection.