A foldable portable cellular phone capable of identifying a transmitter of an incoming call to which a response has not yet been made is provided. At least one of the input point and points encrypted by performing elliptic curve operation over a plurality of rounds may be randomly selected based on the randomness rate and the random position value. Multibank refresh is made possible by varying the current profile for the row sense and row precharge currents during a refresh operation, as compared to normal memory access.