Most current systems have ignored security vulnerability concerned with boot firmware. It is highly likely that boot firmware may cause serious system errors, such as hardware manipulations by malicious programs or code, the operating system corruption caused by malicious code and software piracy under a condition of no consideration of security mechanism because boot firmware has an authority over external devices as well as hardware controls. This paper proposed a structural security mechanism based on software equipped with encrypted bootstrap patterns different from pre-existing bootstrap methods in terms of securely loading an operating system, searching for malicious codes and preventing software piracy so as to provide reliability of boot firmware. Moreover, through experiments, it proved its superiority in detection capability and overhead ranging between 1.5 % ~ 3 % lower than other software security mechanisms.