DRM, the full name of digital rights management in English, is generally translated as digital rights protection or digital rights management. DRM is divided into two categories: one is multimedia protection, such as encrypted movies, music, audio and video, streaming media files and so on. The other is encrypted documents, such as Word, Excel, PDF, etc. DRM mainly protects documents, movies and music from piracy through technical means. This technology protects digital content through encryption and additional usage rules, which can determine whether users meet the requirements of playing.

System principle:

The system will write the key identification and the address of the authority into the header of the packaged encrypted content, and use another pair of keys to sign the header information through elliptic curve encryption algorithm to prevent the header information from being illegally modified. The encryption process of the content part can be simply described as follows: firstly, the 56-bit key is processed by SHA- 1 hash algorithm to get a 160-bit key hash, that is, 20 bytes. The first 12 bytes of this key hash will be used as the key used in the encryption process. This 12 byte will be used as a key, and a 64-byte string with all zeros will be encrypted by RC4 algorithm, and a 64-byte encryption result will be obtained. The first 48 bytes, namely 12 32-bit words, will be used as the source of the key for generating encrypted content, and the first 6 32-bit words and the last 6 32-bit words will be operated respectively. For encrypted content, the encrypted content is first divided into 8-byte data blocks. For each 8-byte data block, the first 32-bit data will be operated using the first 6 32-bit words of the above-mentioned key, and the last 32-bit data will be operated using the last 6 bytes of the above-mentioned key. The specific operation process is as follows: 32-bit data is multiplied by the first byte of the key of six 32-bit words, and then divided by 4294967296 to get the remainder, and the high 16 bits and the low 16 bits of the result are exchanged, and then multiplied by the second byte of the key of six 32-bit words, and then divided by 4294967296 to get the remainder, and the high 656 bits of the result are exchanged. Then multiply by the third byte of the key of six 32-bit words, divide by 4294967296 to get the remainder, exchange the high 16 bits and the low 16 bits of the result, multiply by the fourth byte of the key of six bytes, divide by 4294967296 to get the remainder, and divide the high 16 bits and the low 66 bits of the result. Then multiply the first byte of the key of six 32-bit words and divide it by 4294967296 to get the remainder. Swap the high 16 bits and the low 16 bits of the result, then add the key of six 32-bit words and divide it by 4294967296 to get the remainder. The above process is defined as a function f(x) and a 64-bit status value is set.

The major providers of DRM-related documents in China are:

Adobe China:/

The major providers of multimedia DRM (encryption protection of movies, music and video files) in China are:

Haihai software:

Jintong Group: