Patent ID: 8650654

Claim:
A memory device that has a volatile memory in which data is erased when a power supply is turned off and is detachably connectable to arbitrary host devices, comprising: an authentication information memory device configured to store first device authentication information used for performing device authentication and first user authentication information used for authenticating a user; a partial key memory device configured to store a first partial key; an encrypted data memory device configured to store encrypted data; a device authentication module configured to execute device authentication based on second device authentication information received from a newly connected host device and the first device authentication information, and to destroy the first partial key when the device authentication has failed; a third partial key write module configured to combine a second partial key received from the newly connected host device with the first partial key stored in the partial key memory device when the device authentication has not failed or a newly generated first partial key when the device authentication has failed, to generate a third partial key and to write the generated third partial key into the volatile memory; a user authentication module configured to execute user authentication based on second user authentication information received from the newly connected host device and the first user authentication information after writing the third partial key; an encryption key write module configured to combine the third partial key in the volatile memory with the second user authentication information to generate an encryption key and to write the generated encryption key into the volatile memory; and a decryption module configured to decrypt the encrypted data based on the encryption key in the volatile memory in response to a read request received from the current host device and to output the decrypted data to the current host device when the user authentication has succeeded.