Crum chip and smart card

A method of operating a customer replaceable unit monitor CRUM integrated circuit (IC), comprising:

• operating in a test mode and operating in a user mode, wherein:
• operating in the test mode includes:
• performing decryption of an encrypted test code to generate a decrypted test code;
• storing the decrypted test code in a volatile memory;
• and
• turning off a security function of the CRUM IC while performing a test command for performing a wafer level test on the basis of the decrypted test code, and
• operating in the user mode includes:
• performing authorization in response to an encryption key received from a host;
• and
• monitoring the CRUM IC using a user code stored in a read-only memory.

A smart card, comprising:

• a secure module to receive an encryption key and an encrypted test code from outside;
• and
• an information processing module controlled by the secure module, wherein:
• the secure module performs authorization on the basis of the received encryption key,
• the secure module performs decryption of the encrypted test code to generate a decrypted test code,
• the secure module stores the decrypted test code in a volatile memory, and
• the secure module generates a test command for performing a wafer level test based on the decrypted test code in the volatile memory, and provides the test command to the information processing module.