A cryptographic processing apparatus includes: at least one register configured to store data for operation; a first operation block configured to execute an operation in accordance with data stored in the register; a second operation block configured to execute a logic operation between one of a register-stored value and a key and an operation result of the first operation block; and a decode block configured to decode binary data in units of the predetermined number of bits to convert the binary data into decode data having the number of bits higher than the number of bits of the binary data.