To provide a system for delivering programs for communicators that makes it possible to automatically encrypt and decrypt data among information terminal devices at communicators, while also making it possible to enhance security at the communicators.

A variety of software programs, such as for chatting, bulletin boards or email, are delivered from a server 2 to a plurality of information terminal devices 1. The system is used for the communicators for allowing the information terminal devices 1 to communicate information to one another over a network. Unique encrypted information corresponding to the information terminal device 1 is embedded in a source program according to a request from the information terminal device 1. After the source program with the unique encrypted information embedded therein is converted into an object program that can be executed at the information terminal device 1, the object program is sent to the information terminal device 1 via the network.