| 摘要 |
PURPOSE: A method for codifying digital data file is provided to prevent the recovery of file stream by codifying the codified key itself and preventing the decoding of codified key even when the codified key is extracted in file stream. CONSTITUTION: A method for codifying digital data file is composed of connection, reception, and codification. Portable MP3 player(2), which will download the files, connects to PC through the interface, requests and receives information regarding the serial number of the memory used by the MP3 player or PC through the prearranged control commands. User authentication process is eliminated because MP3 player receives and uses the serial number of the device, which enables the MP3 player to download files from itself. To prevent hacking, 1st internal key, which has been prearranged by the two devices, is attached to execute the process of converting the serial number into a code key. 1st internal key can attach a single number or multiple numbers to the serial number to complicate the decoding process. According to the prearrangement between the two devices, the 2nd internal key codifies the previously codified key. The new algorithm, different from the algorithm that was used for previous codification, can be used but due to the portable MP3 player's low execution capability microprocessor, same file codification algorithm is used. It reduces the program memory size needed to store additional algorithm and improves the effectiveness of the execution. During this process, an internal key is attached to the downloading device, which is codified to make it unidentifiable, files are codified using the code key and transmitted to the MP3 player. |
