According to one embodiment, encrypted secret identification information (E-SecretID) and the key management information (FKB) are read from a memory device. Encrypted management key (E-FKey) is obtained using the key management information (FKB) and index information (k). The index information (k) and the encrypted management key (E-FKey) are transmitted to the semiconductor memory device. An index key (INK) is generated using the first key information (NKey) and the received index information (k). The encrypted management key (E-FKey) is decrypted using the index key (INK) to obtain management key (FKey), which is transmitted to the host device.