Method of obtaining a main key from a memory device, method of generating authentication information for a memory device, an external device and system icluding the external device

An external device, comprising:

• a first decrypter configured to receive an encrypted first decryption key from a memory device, the encrypted first decryption key being an encrypted version of a first decryption key, the decrypter configured to decrypt the encrypted first decryption key using a second decryption key to obtain the first decryption key;
• a second decrypter configured to decrypt an encrypted main key received from the memory device using the first decryption key to obtain the main key, the external device unable to directly read the main key from the memory device.

A method for an external device to generate authentication information for authenticating a memory device, comprising:

• generating, at the external device, a session key based on spare key information, the spare key information including information regarding a spare key used by the memory device to generate first authentication information;
• generating, at the external device, second authentication information based on the session key and a derived main key, the derived main key being a main key of the memory device, the external device being unable to read the main key from the memory device.

An external device, comprising:

• a session key generator configured to generate a session key based on spare key information, the spare key information including information regarding a spare key used by the memory device to generate first authentication information;
• an authentication information generator configured to generate second authentication information based on the session key and a derived main key, the derived main key being a main key of the memory device, the external device being unable to read the main key from the memory device.

A system, comprising:

• a memory device configured to store a main key and at least one spare key in a first memory area, the memory device configured to store an encrypted main key and at least one spare key index in a second memory area, and the memory device configured to store at least one encrypted decryption key, the memory device configured to generate first authentication information based on the main key and the spare key, the memory device configured to permit an external device to access the second memory area but not the first memory area;
• the external device, the external device configured to access the encrypted main key, the spare key index and the encrypted decryption key, the external device configured to generate a derived main key based on the encrypted main key and the encrypted decryption key, the external device configured to generate second authentication information based on the spare key index and the derived main key, and the external device configured to determine whether the memory device is verified based on the first authentication information and the second authentication information.