Encryption device

An encryption device comprising:

• a register;
• an input circuitry configured to receive plain data;
• a first partial encryption circuitry configured to calculate first intermediate data from the plain data;
• a second partial encryption circuitry configured to calculate (i+1)-th intermediate data based on i-th intermediate data and an encryption key, wherein i is an integer equal to or greater than one and smaller than N, and N is a predetermined integer equal to or greater than two;
• a first transform circuitry configured to:
• transform j-th intermediate data into j-th transformed data, wherein j is an integer equal to or greater than one and equal to or smaller than N;
• and
• store the j-th transformed data in the register;
• a second transform circuitry configured to transform the j-th transformed data stored in the register into the j-th intermediate data;
• a third partial encryption circuitry configured to calculate encrypted data from the N-th intermediate data;
• an output circuitry configured to output the encrypted data;
• and
• a random number generation circuitry configured to generate a random number, wherein
• the second partial encryption circuitry is further configured to repeat processing to calculate (j+1)-th intermediate data while j is equal to from 1 to N−1, the processing being repeated based on the j-th intermediate data and the encryption key, the j-th intermediate data being transformed from the j-th transformed data by the second transform engine,
• the first transform circuitry is further configured to:
• transform the random number into a transformed random number using a predetermined first transform processing;
• store the transformed random number in the register;
• and
• transform the j-th intermediate data into the j-th transformed data,
• the j-th transformed data being masked with the random number, and
• the second transform circuitry is further configured to:
• transform the transformed random number stored in the register into the random number using a second transform processing,
• the second transform processing transforming the transformed data after the transform by the first transform processing into the data before the transform by the first transform processing;
• and
• transform the j-th transformed data stored in the register into the j-th intermediate data,
• the j-th intermediate data being released from the mask using the random number, and
• the random number not being stored in the register.