A recording apparatus is disclosed, that comprises a compression process means for compressing an input digital signal corresponding to a predetermined compression process and segmenting the compressed digital signal into blocks, a fixed value generating means for generating a predetermined fixed value, an adding means for adding the fixed value generated by the fixed value generating means at a predetermined timing to the blocks of the digital signal compressed by the compression process means, an encrypting means for encrypting the fixed value and the compressed digital signal added by the adding means, and a recording means for recording the fixed value and the compressed digital signal encrypted by the encrypting means to a record medium.

 
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> Security method using information transmission by optical means, and an optical disk for implementing the method

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