PURPOSE: To stop data from being deciphered when it is deliberately read out by managing an individual key (data cipher key) for an auxiliary recording medium by an IC chip.

CONSTITUTION: Based on the ID No. of an auxiliary recording medium 21, an IC chip 22 prepares an individual key for the auxiliary recording medium 21 in a built-in individual key preparation section and records a cipher data ciphered by the auxiliary recording medium 21 when recording a secret data in the auxiliary recording medium 21. When reading out the cipher data, the chip prepares the individual key based on the ID No. of the auxiliary recording medium 21, deciphers the cipher data which has been read out. Thus, the data ciphering individual key for the auxiliary recording medium 21 is secretly managed by the hybrid card IC chip 22, so the individual key for the auxiliary recording medium 21 is not leaked out and there is hardly any fear of the cipher data being read out or deciphered.