Research And Design On Software Protection System Based On Virtual Machine

Software is a technology-intense digital product.While the development of software needs immense human and material resources,to make a copy of software is very simple. So the copyright protection of software is a troublesome problem. The usual protection schemes are serial,license file,packer, etc.But the protection effect isn't very good.Virtual machine(VM) protection scheme makes the critical code run as pseudo code under VM.It can increase the time complexity to reverse the software.If the cost to crack the software exceeds the cost to buy the software,then the effect of the protection is achieved in fact.The design of VM involves operating system,programming language and the architecture of computer. Virtual machine can be divided into two types:stack-based VM and register-based VM.The difference depends on the ISA(instruction set architecture). VM is a Von Nouma architecture computer,that is to say,a program is stored and executed.The execution of program includes instruction-fetch, instruction-decode and execution.On the base of analyzing the usual software protection and cracking methods , the VM protection design is discussed in detail. A register-based virtual machine called SRVM64 (Secure Register-based 64 bits Virtual Machine) is provided.And the design of ISA is discussed.And a super-instruction set is provided.Then the working procedure of VM Interpreters and the VM code generation are researched. After that,a C sub-set programming language and VM assembly language are provided.And the compiling technology is discussed.Since every protection method has its own applicability and limitation,it's necessary to use a various protection methods together.A VM-based software protection system integrating various protection schemes is designed.To defeat the usual software cracking methods,it uses self-checking, anti-dissamble, anti-debug, packer, strong encryption algorithm,watermark and VM protection. However,this system can increase the complexity of revesing and the cost of cracking, provide flexible software licensing mechanism,and will achieve the remarkable effect of protection.The VM-based software protection system explores using VM to implement software protection.If we improve the system,such as enriching the instruction set and adding the fuction of exception and interrupt processing,,the software protection scheme based on virtual machine will have a broad prospect.