An electronic circuit includes an operator including logic gates configured to perform either one or both of encryption and decryption operations. The electronic circuit further includes a controller configured to control the operator to operate in a first mode in which each of the logic gates outputs a first logic value during a first time period of a clock signal, and operate in a second mode in which a number of first logic gates, each of which outputs the first logic value, among the logic gates, and a number of second logic gates, each of which outputs a second logic value, among the logic gates, are maintained constant during a second time period of the clock signal, in response to a control value indicating that either one or both of the encryption and decryption operations are performed.