Encription device and decryption device

An encryption device that performs encryption processing using an secret key and calculates encrypted data from plain data, the encryption device comprising:

• a storage unit;
• an input unit that receives plain data;
• a first partial encryption unit that calculates first intermediate data from the plain data and stores the first intermediate data in the storage unit;
• a generation unit that generates a round key, which is used in calculations for the first intermediate data and N-th intermediate data (where N is an integer equal to or greater than 2), from the secret key;
• a second partial encryption unit that calculates (i+1)th intermediate data on the basis of i-th intermediate data (where i is an integer equal to or greater than 1 and smaller than N) and the round key, and stores the (i+1)th intermediate data in the storage unit;
• a third partial encryption unit that performs an arithmetic operation including predetermined conversion for mixing the N-th intermediate data, calculates (N+1)th intermediate data, and stores the (N+1)th intermediate data in the storage unit;
• a fourth partial encryption unit that obtains encrypted data by performing an arithmetic operation including inverse conversion of the conversion on the (N+1)th intermediate data;
• and
• an output unit that outputs the encrypted data.