In order to protect against unauthorized duplication of a library file, or the like, according to the present invention, an executable module is generated. The executable module is generated by generating, with decryption of an encrypted protective object, a protective object containing a procedure for terminating a process operation due to invalid relationship between a first protect code and a second protect code contained in the executable module, linking the resultant decrypted protective object with other object, and writing a protect code. Then, the decrypted protective object is deleted after linking with the other object.