Research Of Architecture And Key Technology Of Java Smart Card Operating System

Java Card is a mixed hardware and software systems which via software building,and support the downloading,installation and operation of Java program,and adopt Java technology in the smart card and run on the basis of smart card hardware.Java card has been widely used in many fields which including finance,telecommunications,health care,transportation,etc.,with a high application and research value.JCRE(COS)has been a hotspot and difficulty of academic studies as the most central part of Java Card.Java Card technology has been facing a technical problem which is how to use the limited memory resource of Java Card efficiently and improve the efficiency of Java Card System.We usually use two solutions:One is just take a valid subset of Java language to support the Java Card System.The other is dividing the Java Card virtual machine into two components which including Off-card and On-card.Conventional solutions often focus on one aspect,either the bytecodes or the virtual machine;the effect of optimization is not significant.By studying the research results of previous,analyzing the advantages and disadvantages of bytecodes optimization scheme and virtual machine optimization scheme carefully.This thesis proposed a hybrid optimization based on the two optimization schemes,generally around two aspects.In the aspect of bytecodes optimization,this thesis proposed an optimization scheme based on the folding compression mechanism.Using a way which mixed the extended instruction set and dictionary compression and processing the byte code file.Firstly,we optimize bytecodes file via the method of extended instruction set,this process produces the CAP file.Then optimize the CAP file via the method of dictionary compression algorithm.This process is carried out at the Off-card,and compressed partly.The CAP file is smaller than the previous file after the process of optimization,and saving storage space.In the aspect of dynamic memory management optimization of JCVM,Firstly,we analyze the model of cache optimization and the memory access mechanism of JCVM,and then introduce a new architecture of JCVM,which transferred the creating work of most objects from EEPROM to RAM,This process will produce fragmentation.This thesis propose a new dynamic memory management scheme which is based on the ideological of generational recycling,and lead into the train collection algorithm,then describe the storage rules via the DSL language.This will not only improve the efficiency of the system,but also achieve the effective management of memory fragmentation to some extent.Finally,we present the experimental program of this thesis,by analyzing the theory and comparing the performance of before and after optimization,which demonstrates the effectiveness and feasibility of the hybrid optimization scheme.