The Research And Implementation On Algorithm Of On-card Bytecode Verification For Java

Java card is widly used in the highly security fields such as bank, communication etc. Byte code verification on the Java card is an indispensable part for a safe embedded system. Traditional byte code verification is infeasible as limited by the space of the Java card itself and the capability of the arithmetic unit. To solve this problem, three algorithms, namely a cache policy based algorithm, a CFT (Control Flow Tree) based algorithm, and a hybrid algorithm, are attempted for the byte code verification on the Java card in this paper.The key points of this paper are designing and implementing on-card Java card byte code verification algorithms to solve the time and space limition of traditional algorithm. Based on analyzing the translated byte code files construction and the hardware resources on card, an effective on-card cache policy is designed and adopted after translating the byte code files in the off-card part. The algorithm based on cache policy and that based on CFT are prsented first. Then a new hybrid algorithm is proposed to trading off the disadvantage of the previous two algorithms. These three algorithms improve the traditional algorithm efficiency on aspects such as time complexity, space complexity and time-space complexity respectively. And then the detailed schemes of Java card on-card verifier based on off-card translation and on-card cache policy, building environment for development, rewriting the Java card virtual machine, implementing off-card translater and so on are put forward. At last the result of this paper and some suggestions of improving the verification efficiency in the future are presented.