A scheme for distributing executable programs through a network from a program distribution device to a client device having a tamper resistant processor which is provided with a unique secret key and a unique public key corresponding to the unique secret key in advance is disclosed. In this scheme, a first communication path is set up between the program distribution device and the client device, and a second communication path directly connecting the program distribution device and the tamper resistant processor is set up on the first communication path. Then, the encrypted program is transmitted from the program distribution device to the tamper resistant processor through the second communication path.