Encryption device

An encryption device which performs encryption processing for encrypting plain data to encrypted data, the encryption processing including nonlinear transform processing, the encryption device comprising:

• a mask processing unit which calculates masked plain data on the basis of the plain data and a first mask;
• a segmentation unit which segments the masked plain data into a plurality of pieces of first segmented data;
• a first processing unit which performs predetermined first processing on the plurality of pieces of first segmented data to generate a plurality of pieces of second segmented data;
• a nonlinear transform unit which generates a plurality of pieces of third segmented data transformed from the plurality of pieces of second segmented data;
• a second processing unit which performs predetermined second processing on the plurality of pieces of third segmented data to generate a plurality of pieces of forth segmented data;
• a data integration unit which integrates the plurality of pieces of forth segmented data to generate masked encrypted data;
• and
• an unmask processing unit which generates the encrypted data on the basis of the masked encrypted data and the second mask,
• wherein the exclusive OR of the plurality of pieces of second segmented data matches the exclusive OR of input data, which is to be subjected to the nonlinear transform processing and is calculated from the plain data, and the first mask, and
• wherein the exclusive OR of the plurality of pieces of third segmented data matches the exclusive OR of transform data, which is obtainable when the nonlinear transform processing is performed on the input data, and the second mask.