Patent ID: 8204219

Claim:
A cryptographic method for enhancing computation performance of a central processing unit, the central processing unit executing a conversion function of the cryptographic method, the conversion function comprising a bit expansion operation, a bitwise exclusive OR operation, a series of selection operations and a plurality of bitwise logical operations, the selection operations requiring the use of a plurality of substitution boxes, the method comprising the steps of: (A) detecting a processing bit length of the central processing unit; (B) generating at least one new substitution box from original substitution boxes according to the processing bit length and a bit permutation sequence, each of the at least one new substitution box containing a plurality of new substitution values whose bit length is equal to the processing bit length; and (C) using the bit expansion operation, the bitwise exclusive OR operation, the selection operations that utilize the at least one new substitution box generated in step (B), a plurality of bitwise AND operations, and at least one bitwise OR operation to conduct the conversion function.