I. Introduction

Digital rights management (DRM) refers to the use of technology, management, law and other means to protect the legitimate rights of digital rights owners, to prevent the illegal use of rights content and ensure the interests maximization of all parties in the industry chain [1]. So DRM is the basis for supporting and safeguarding a healthy and orderly media industry ecology. At present, DRM technology is facing unprecedented challenges and new development opportunities due to the development of 4K, media convergence, 5G, artificial intelligence, block chain and many other emerging technologies. In 2004, with the support of SARFT and the government, ChinaDRM forum organized all parties in the domestic radio and television industry chain to formally establish, jointly discuss the technology of digital rights management, and draft relevant standards of ChinaDRM. By 2019, the forum has 87 member units, covering all links of the end-to-end industrial chain in the field of radio, film and television, and has built the ChinaDRM ecosystem, including ChinaDRM 4K-DRM working group, DRM client working group, ChinaDRM laboratory, rights monitoring and protection platform, China Radio, film and television digital rights management certification center (CDTA), DRM CERTIFIED (DRMC). In 2014, ChinaDRM forum issued the standard GY/T 277-2014 [2], and after extensive solicitation of opinions, the revised standard GY/T 277-2019 [3] was officially released in July 2019, replacing GY/T 277-2014. At present, all industrial chains are carrying out research and development work with GY/T 277-2019 as the standard. In this standard, the key technologies of digital rights management for broadcasting and television are specified, and the digital rights management system architecture, content encryption method and encapsulation formats, license format, license acquisition protocol, DRM client and server are fully explained. The standard is applicable to rights management of live and on-demand content in digital TV, IPTV, Internet TV, Internet video and other application scenarios. The cryptographic algorithms used in the standard are all domestic cryptographic algorithms. The video and audio encoded data is used algorithms for encryption. Content encryption does not affect the conversion of encapsulation formats. One encryption can support multiple streaming media formats such as HLS and DASH. At the same time support AVS2 [4], H.264, H.265 and other encoding methods, also supports TS, MP4 [5] and other content encapsulation formats. This article will focus on the video and audio encoding methods and content encryption methods mentioned in the standard, and propose a decryption method for encrypted streams. Using this method to decrypt the bitstream, and then through the conversion of the packaging format, the tester can play the corresponding media file on the computer or Web browser.