PROBLEM TO BE SOLVED: To permit a transmitter to inexpensively transmit data whose content is desired to be secret to a receiver by the prescribed time by decoding ciphered data through the use of a common key transferred through a synchronous transmission network and opening the content of data to a receiver at time for which the transmitter schedules. ;SOLUTION: Data inputted from a data output device 101 to the open time controller 102 of a transmission side are ciphered by using a common key and an identification number is added to it. Data to which the identification number is added are transferred to an asynchronous transmission network connection device 103, are assembled into a packet and transferred to an asynchronous transmission network connection device 105 through an asynchronous transmission network 104. The packet transferred to the asynchronous transmission network connection device 105 is separated into a header and data with identification number. Separated data with identification number are inputted to the open time controller 106 of a reception side and separated into the identification number and ciphered data. Separated ciphered data are decoded by using the common key and inputted to a data input device 107.;COPYRIGHT: (C)2001,JPO
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