Encoding apparatus and method

An encoding apparatus based on a white-box advanced encryption standard (AES), the encoding apparatus comprising:

• 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, wherein the instruction comprises:
• 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 using 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,
• wherein a, i, and j are each a natural number of 1 or more,
• wherein when the additional encoding is performed on the data in the a-th round, the instruction further comprises an instruction for additionally decoding the data obtained by the additional encoding among data obtained by encoding using the second table in an (a+1)th round and then encoding the data obtained by encoding using the second table using the first table for looking up and calculating a result value obtained by encoding according to a predetermined pattern,
• wherein the instruction further comprises an instruction for creating additional encoding information indicating whether the additional encoding is performed, and
• wherein the encoding using the first table of the data obtained by encoding using the second table comprises determining whether the additional encoding is performed on the data in the a-th round with reference to the additional encoding information.