Electronic device capable of protecting confidential data

A method for operating an electronic device, the electronic device comprising a first non-volatile memory and an application circuit comprising a second non-volatile memory, a first decryption unit, an encryption unit, a second decryption unit, and a functional unit, the method comprising:

• the first non-volatile memory storing a first encrypted data encrypted with a global key;
• the second non-volatile memory storing the global key;
• the first decryption unit retrieving the global key from the second non-volatile memory;
• the first decryption unit decrypting the first encrypted data with the global key to generate plain data;
• the encryption unit encrypting the plain data with a local key to generate second encrypted data;
• the encryption unit overwriting the first encrypted data in the first non-volatile memory with the second encrypted data;
• after the encryption unit overwrites the first encrypted data in the first non-volatile memory with the second encrypted data, restarting the application circuit, and the first decryption unit retrieving the global key from the second non-volatile memory, and performing a decryption with the global key;
• in response to failure of the decryption, the second decryption unit decrypting the second encrypted data with the local key to obtain the plain data;
• in response to correctly decrypting the second encrypted data with the local key, the functional unit performing operations according to the plain data;
• and
• in response to failure of the decryption and failure of decrypting the second encrypted data with the local key, terminating the application circuit.