Abstract: System for controlling communication between electronic information cards, such as IC-cards and a host computer, to be kept in secret. In order to protect the data, various countermeasures have been proposed in which the data are enciphered to be sent and deciphered for reading out. There is a problem, however, the cyphograph is difficult to keep secret when it is used for a long time. The invention intends to provide a device having at least two connectors for an IC-card stored with an algorithm for enciphering the data and another IC-card or other IC-cards for making communication with the host computer so as to readily change the first IC-card with a new one storing another algorithm.