To make automatically updatable an account by executing a lot of financial transactions without trouble by executing the financial transaction with access through a personal digital assistant(PDA) and transmitting updated information on respective financial accounts from respective financial institutions to the PDA.

The PDA 10 communicates with a shop computer system 20 through kiosks 14A-14E. A PDA user selects a financial account and an amount to be subtracted. When the final transaction total is covered by that selection in the case of judgement of whether the financial transaction amount is covered by the selection or not, the user inputs an account approval instruction such as password, personal identification number or voice recognition approval concerning each account selected to be subtracted. Financial institution computer systems 30-34 receive cryptographic keys from the PDA 10 and the shop computer system 20 and return them. The current account information is transmitted to the PDA 10 and the user obtains this information and completes the final transaction.