| 摘要 |
Bit "0" and bit "1" constituting a digital signal are replaced with extended length binary coded signals. For example, bit "0" of the digital signal is replaced with "011", and bit "1" with "110". The replaced signals are recorded in a non-rewritable recording medium. A bit "0" of the recorded signal does not change a status of the recording medium whereas a bit "1" of the recorded signal changes the status of the recording medium. Unauthorized change of the data recorded in the recording medium can be recognized if the data read on a three-bit basis indicates "111". A header may be additionally recorded in the recording medium to store status of the data recorded therein.
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