| 摘要 |
Data for protecting software is written into a ROM for protecting software in an IC card including other ROMs for storing data and scrambled software. The data for protecting software provides a key for execution of the software. A read-write RAM is responsive to the same select signal that is applied to the software protecting ROM for reading and writing of data by a user. When the data of the software protecting ROM is read out, the outputs of the ROM and the RAM are exclusive-OR gated. Accordingly, it is impossible to easily know what software protection data has been written into the ROM, i.e., to decode the software key. The ROM, the RAM, and the data processing circuit may be constructed as one IC.
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