An electronic device and a method of operating the electronic device are provided. Data corresponding to a user input is received through a user interface of the electronic device. The data is stored in a normal area of a memory of the electronic device. A quantity of information in the stored data is identified. At least one key is selected from a plurality of keys stored in the memory, based on at least the quantity of information. The data is encrypted using the at least one key. The encrypted data and information indicating the at least one key are transmitted to a secure area of the memory, which requires access authority.