A terminal device includes, as functions for transmitting a file with a digital signature via mail, a first communication unit for carrying out communication with a terminal device used by an authorizer when a distance from that terminal device is not greater than a prescribed distance, an obtaining unit for obtaining a value obtained from a file to be transmitted, which has been encrypted through encryption processing performed by making use of information exchanged with that terminal device, and a transmission instruction unit for outputting an instruction for mail transmission of the file and the obtained encrypted value.