Study Of Java Bytecode Safety Technology Base On Obfuscation And Watermark

Java programs have been popularized in the internet because of platform dependence characteristic. Meanwhile java programs also have two serious safety problems:The first one is using infringement. The fact that java compiler compile a class into a separate class file makes easy for java using infringement;The second one is reverse engineer.At present java decompilation technology has already reached maturity,there are many java decompilation tools which can compile java bytecode into source code very well.The thesis proposes a new software protection model :prottecting java bytecode's safety by the way of code obfuscation and software watermark technology,accordingly protecting java softwares'intellectual property rights,Obfuscating Java bytecode can exactly hide program's inner information on the premise of keeping programs'function,which makes java programmer difficult to understand the code after decompilation even be unable to recompile correctly more even be unable to decompile. Watermark which is embedded in java bytecodes is information which has special meaning. The thesis makes use of obfuscation technology to prevent java bytecode from reverse engineer,makes use of software watermark to comfirm the class file which is stolen or not and provide copyright protection with java class file.Existing code obfuscation technology is studied.The thesis designed the lexcial conversion algorithm and class's false refactor algorithm,the thesis improved,perfected the class split algorithm,and summarized the difference of type hide obfuscation's essence and interface call-back technology,the thesis analysed three control flow obfuscations which make decompile fail,and find out two obfuscation strategies aiming at the problem which program slice threatens control flow obfuscation. The thesis studied a java bytecode watermarking algorithm which increases watermarking algorithm's resistibility and transparency by the betterment.Aim at the theory study result, The thesis designed and realized the system whose name is JOCOW(Java Tool which combines obfuscation and Watermark technology),the users use the system to provided double protection to Java bytecode.It is impossible to protect kava bytecode's absolute safety,but it can provide copyright protecttion for java bytecode and make reverse engineer meaningless.