Memory device, memory system, and authentication method

A memory system comprising:

• 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;
• and
• a legitimate host device having a connection right with respect to the memory device in the arbitrary host devices,
• wherein the memory device comprises:
• an authentication information memory device configured to previously store first device authentication information used for performing device authentication with respect to the legitimate host device and first user authentication information used for authenticating a proper user who utilizes the legitimate host device;
• a partial key memory device configured to previously store a first partial key constituting a part of an encryption key written into the volatile memory;
• an encrypted data memory device configured to store encrypted data which is data encrypted based on the encryption key;
• a device authentication module configured to execute device authentication based on second device authentication information received from a newly connected current host device and the first device authentication information in the authentication information memory device and to discard 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 current host device with the first partial key in the partial key memory device and to write a generated third partial key into the volatile memory after the device authentication;
• a user authentication module configured to execute user authentication based on second user authentication information received from the current host device and the first user authentication information in the authentication information memory device 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 and to write a generated encryption key into the volatile memory after the user authentication;
• 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 obtained data to the current host device when the user authentication has succeeded, and
• the legitimate host device comprises:
• a device authentication information memory device configured to store the second device authentication information;
• a device authentication information transmission module configured to transmit the second device authentication information in the device authentication information memory device to the memory device in accordance with a specified authentication sequence of the device authentication executed by the device authentication module when the memory device is connected;
• a user authentication information acceptance module configured to accept input of the second user authentication information;
• a user authentication information transmission module configured to transmit the accepted second user authentication information to the memory device;
• a read request acceptance module configured to accept input of the read request;
• and
• a read request transmission module configured to transmit the accepted read request to the memory device.

An authentication method executed by 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,

• the method comprising:
• previously writing first device authentication information used for performing device authentication with respect to a legitimate host device having connection authority in the arbitrary host device;
• previously writing first user authentication information used for authenticating a proper user who uses the legitimate host device;
• previously writing a first partial key constituting a part of an encryption key written into the volatile memory;
• encrypting data based on the encryption key and writing obtained encrypted data;
• executing device authentication based on second device authentication information received from a newly connected current host device and the first device authentication information and discarding the first partial key when this device authentication has failed;
• combining a second partial key received from the current host device with the first partial key and writing generated encryption key into the volatile memory after the device authentication;
• executing user authentication based on second user authentication information received from the current host device and the first user authentication information after writing the third partial key;
• combining the third partial key in the volatile memory with the second user authentication information and writing a generated encryption key into the volatile memory after the user authentication;
• and
• decrypting the encrypted data based on the encryption key in the volatile memory and outputting obtained data to the current host device in response to a read request received from the current host device when the user authentication has succeeded.