1. A software encoding and decoding method comprising: software encoding step for encoding a software by combining at least two encoding basic algorithms; and software decoding step for inputting encoded software and for decoding said software with decoding basic algorithms corresponding to said at least two encoding algorithms used in said encoding step; wherein said software encoding processing step includes a step of transferring information concerning said combination of said at least two algorithms used for encoding together with the encoded software; and wherein said software decoding processing step includes a step of selecting decoding algorithms based on said information of the combination of said encoding algorithms.