Smart Card Memory Management System Design And Implementation

Smart cards are widely used because of their security and portability, however,with the rapid increase of expanding the number and distribution of applications, the number of cards held by a single user will be rapidly increased, which will greatly affect the portability. UCard its core idea is the introduction of new hardware and software technologies to accommodate multiple publishers across multiple chip operating system(COS) on a single card, the new smart card structure is given in response to this situation, it to overcome the existing "a multi-purpose card" model exists confidentiality and security issues, then the so-called multi-issue is implemented, so it can be used as many traditional smart cards. It gives a solution for portability problem, with the secrecy and security guaranteed.In order to achieve the goal, the key problem in UCard structure is to guarantee that its several COSs can coexist in one memory space but keep isolated at run-time,especially to prevent the running COS from accessing the private memory resources of other COSs. This characteristic of UCard makes it so different with traditional smart cards.After the memory management model of UCard was researched, some definitions are given, then the constraints and other mathematics relations between different memory spaces and addresses are analyzed. The memory allocation of UCard was researched, and some feasible allocation methods were given.There are several COSs in UCard, the decision of which one is chosen to run can only be made after the interaction with card user, so the corresponding physical memory addresses of the logic addresses given by CPU are uncertain. A dynamic address mapping is needed. After comparing with the mathematics model of traditional smart card address bus, the address mapping in UCard was deeply analyzed, then the concept of Programmable Dynamic Address Bus is brought forward. Two methods of PDAB implementation were analyzed, and three ways to protect PDAB control parameters were given.To validate the feasibility of UCard design, and for subsequent research, a hardware simulation system based on dual CPUs was designed and implemented, at the same time, some programs for memory management and dynamic address mappingwere made. The block-choosing based method of PDAB design was implemented, and the PDAB control parameters can be protected by the scheme of putting PDAB control module and COS on co-processor and main processor separately. With PDAB, it’s guaranteed that the running COS can’t access the private memory resources of other COSs, the anticipated goal of UCard simulation system are achieved, and the feasibility of the idea of UCard was validated.