Electronic device for selecting key to be used for encryption on basis of amount of information of data to be encrypted, and operation method of electronic device

An electronic device comprising:

• a user interface;
• a processor operatively connected to the user interface;
• and
• a memory operatively connected to the processor and comprising a normal area and a secure area,
• wherein the memory is configured to store a plurality of keys for encrypting data corresponding to a user input, and to store instructions causing the processor, when executed, to:
• receive the data through the user interface;
• store the data in the normal area;
• identify a quantity of information in the data;
• select at least one key from the plurality of keys stored in the memory, based on at least the quantity of information;
• encrypt the data using the at least one key;
• and
• transmit the encrypted data and information indicating the at least one key to the secure area, which requires access authority.