To provide a method and a device, capable of preventing an unauthorized user from accessing a storage device in which data is stored at an encoded state by pretending to be someone else.

Fingerprints of a user to access the storage device 33 in a computer 3 are read by a fingerprint reader 22, data about prescribed fingerprint information stored in a first memory 11 of an IC card 1 are collated with the read fingerprint information, operation algorithm for encoding/decoding stored in a memory 32 is started, only when both pieces of fingerprint information match each other, the data to be stored in the storage device 33 is encoded by an encoding/decoding part 31 and encoded data stored in the storage device 33 is decoded simultaneously.