Research On The Security Technologies Of Some Wireless Embedded Systems

Being a reprentative technology in the fusion of computer science and industrial technology, embedded system security issues, especially wireless embedded system security are paid much more attention on by designers and producers.With the progress of reverse engineering techniques, remapping and microprobing become easier to implement, and eavesdropping of data in hardware layer is feasible. Therefore, how to protect system bus, volatile memory and other hardwares is a vital problem in embedded system. MPU is the core part of an embedded system. With the increase of the degree of integration, improvement of manufacture and packaging, anti-probing and tampering measures, the reverse engineering on MPU is quite impossible. Therefore, MPU is suitable place to reserve overall system secret, so designing and integrating a security scheme into the architecture is the best way to derive the security from MPU to whole system.Besides the security assurance by physical layer, embedded systems require robust and secure applications in upper layers. With the drive of commercial applications, popularization of wireless networks and the concept of ubiquitous computing expedite security towards integrity system design. Wireless embedded system networks focus on two issues: (1) establishing trust among network members, and (2) efficiency and security of protocol itself. Therefore, we select two representative scnarios; wireless sensor networks (WSNs) and low-cost RFID systems. We put a hot research topic on wireless sensor networks because they involve complex network communications and how to establish trust among network members are challenging. Low-cost RFID systems's less power and computation ability also bring a tricky situation which implies that standard cryptographic premitives are impossible to be deployed, so the lightweight and efficiency of security resolution must be prerequisite.Therefore, we compartmentalize security issues on embedded systems into two layers, one is Architectural Security, and the other one is Communication Security. On the Architectural Security layer, we start our research on common computer architecture. After analyzing existing secure architecture framework and memory protection techniques, we obtain the following achievements:First, according to the feature of microprocessor architecture, we designed an efficient memory encryption and verification scheme. This scheme provides architecture support for data encryption outside MPU chip and data verification while accessing main memory. Meanwhile, it adopts GCM encryption mode, the speed of data encryption/decryption and verification is improved, which makes our scheme more efficient than others, and more suitable for embedded system microprocessor architecture. The simulation results reveal that our scheme slows down the system 20% and less, while other schemes cause more than 25% performance slow down.Second, considering the popularization of Chip Multi-Processor (CMP) architecture, we proposed counter Cache coherence optimiazation method AOW for CMP adopting secure architecture. AOW is a"write-invalid"snooping protocol as MESI. It provides 1bit onto MESI protocol to identify the status and keep the freshness of counters. The aim of AOW is to advance the hit rate of counter Cache, so that the times of memory access for missing counter will be obviously reduced. The results of system simulations reveal that AOW protocol promots the system performance at least 8% under SPEC2000 benchmarks.On the Communication Security layer, we choose two representative wireless networks, wireless sensor networks and RFID systems. We obtain the achievements as follows:First, focusing on large amount of unidirectional links in sensor networks, our researches include key establishment protocols which exploit these links in WSNs. We realize that unidirectional links are neglected by most security protocols so that nodes covered by only unidirectional links are no longer available in network activities. We propose IntraKey and InterKey Protcol exploiting unidirectional links in WSNs. These protocols promots the proportion of available nodes in network, and the simulation results prove that. Later on, we implement several cryptographic premitives including an asymmetric key algorithm ECC on XBOW MICAz, and measure the time and energy consuming.Second, for low-cost RFID system, our researches include analyzing the relation between circuit and cryptographic premitive complexity, and compare several lightweight authentication protocols. After the realization of the impossibility of standard cryptographic premitives, we propose a lightweight mutual authentication protocol for low-cost RFID systems adopting only Pesudo-Random Function (PRF), and authenticate each other through three message flows. It also provides forward security and the ability of anti-replay attack and man-in-the-middle attack.