[Objective] When installing software into an in-vehicle terminal from a server, it is required to prevent the software from being installed into an unsuitable terminal, and to reduce time and efforts for data input and download, thereby improving the convenience of the user.
[Solution] In an information distribution system, terminal identification information and a terminal unique key for an in-vehicle terminal are stored in a server as well as in itself. The in-vehicle terminal transmits the terminal identification information to the server for terminal authentication via a communication terminal after encrypting with the terminal unique key, and then the server transmits encrypted software to the communication terminal. The communication terminal transmits the encrypted software to the in-vehicle terminal, which in turn obtains a software unique key encrypted with the terminal unique key from the server and decrypts the encrypted software for installation using the software unique key.