Provided is an encoding apparatus including a communication unit configured to receive data from an outside, a memory configured to store an instruction for encoding the data, and a processor configured to encode the data according to the instruction, in which the instruction includes an instruction for encoding the data using a first table for looking up and calculating a result value obtained by encoding according to a predetermined pattern in an a-th round, and when among first to fourth data included in data obtained by encoding through the first table, an i-th bit of exclusive OR of the second to fourth data and a j-th bit of the first data are different, an instruction for encoding the data using a second table for looking up and calculating a result value calculated by performing additional encoding on exclusive OR of the first to fourth data.