| 摘要 |
Image data is prevented from being stolen by data manipulation. An extractor (111) extracts effective video data and predetermined data from data (110). An inserter (114) inserts a calculation result of the predetermined data outputted by a calculator (113) into the effective video data as encrypted by an encryptor (112). An output from the inserter (114) is supplied through a transmission path (120) to an extractor (144), which extracts the encrypted effective video data and the calculation result data of the calculator (113). A calculator (143) calculates, from the effective video data as decrypted by decryptor (141) and extracted by an extractor (142), in the same manner as the calculator (113) and outputs the data corresponding to the data used in the calculator (113). A comparator (145) compares the output from the calculator (143) with the calculation result extracted from the data (140). If they are not coincident, it is judged that there exists a possibility that the transmitted data has been manipulated, and an output from a different output generator (146) is outputted as output data (148).
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