To perform a medium conversion processing through a network while preventing the leakage of information by automatically selecting the information of a ciphering system most suitable for a converted form, ciphering processing data, adding attribute information for indicating a decoding system optimum for decoding the processing data to the processing data and outputting them.
At the time of receiving a medium conversion request from a client, a server performs the conversion processing of data inputted from the client in a medium conversion processing part 13 and ciphers the conversion- processed data in a ciphering/decoding part 17 by the ciphering system most suitable for transmission to the client selected from a ciphering/decoding information library 15 by a ciphering/decoding system selection part 16. Then, the information of the decoding system optimum for decoding is added to the ciphered data in an attribute information addition part 19 and they are sent out from an output part 18. Thus, the data are transmitted to the client while keeping security.
SUGIYAMA HIROSHI
SUMITA KAZUO
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