Abstract: In an information access system, a reader/writer device encrypts, with a first encryption key, an information request and a second encryption key to thereby generate first encrypted data, and encrypts the information request with the second encryption key to thereby generate second encrypted data, and transmits cyclically an information request signal that alternately carries the first encrypted data and the second encrypted data. An active contactless information storage device receives the information request signal and decrypts the encrypted data carried by the information request signal with one encryption key stored in its memory. When the second encryption key different from the one encryption key is contained in the decrypted data, the information storage device rewrites the one encryption key with the second encryption key.