| 摘要 |
PROBLEM TO BE SOLVED: To use a semiconductor memory as a recording medium, to prevent unlimited copies of digital data compressed by a recording device to protect a copyright, and to reduce a memory size to miniaturize a reproducing device. SOLUTION: In this system, a recording device 0 and a reproducing device 20 are provided with an encryption part 4 and a decoding part 2 using a cryptographic key and a decoding key in one-to-one correspondence. A digital signal recorded in a semiconductor memory 40 by the single recording device 0 can be reproduced only by the reproducing device 20 corresponding to the recording device 0. Accordingly, even if the digital signal is copied to plural semiconductor memories 40 with the single recording device 0, only the reproducing device 20 corresponding to that recording device 0 can be used for reproduction. TwinVQ wherein compression calculation for recording has a larger calculation amount than expansion calculation for reproducing is used as an algorithm used in a compression part 2 and an expansion part 24, to reduce the calculation amount in the expansion process. |
