A method of exchanging data stored in a server connected to a network, so that a receiving user can access the data of a sending user, including the steps of encrypting information including at least identification of an item of the data to be exchanged with the receiving user and time information in which the sending user sets the item of data accessible, receiving second information indicating at least identification of an item of the data and a time period in which the item of data becomes accessible, comparing the first information and the second information, and setting the item of the data accessible for the time period if the first information and the second information match.