Patent attributes
An encryption processing device includes an encryption processing section that repeats a round operation on input data and generate output data, and a key scheduling section that outputs a round key to be applied in the round operation to the encryption processing section. The encryption processing section has an involution property in which a data conversion function E and an inverse function E−1 are executed sequentially, and executes the round operation in which a constant is applied once or more in only one of the function E and the inverse function E−1. The constant is a state that satisfies a condition that all of constituent elements of a state which is a result of a matrix operation with the linear conversion matrix which is applied in the linear conversion processing section at a position adjacent to the exclusive-OR section to which the constant is input are nonzero.