Summary: This paper reports on an evaluation result of current obfuscation techniques for Java byte code, such as Collberg's techniques in terms of mutational capability, real-time applicability, and program size increase. We suggest effective obfuscation techniques for random and real-time obfuscation (RR obfuscation). In the evaluation results, the combination of some obfuscation techniques was found to be useful for RR obfuscation, and some obfuscation techniques makes little or no difference after a certain threshold.