System Architecture Design

pSHIELDSystem Architecture DesignPUthird–party users, who might claim and use these modules. The illegal users of an IP block do notnecessarily need to have full, detailed knowledge of the IP component, since IP blocks are independentmodules which can very easily incorporated and integrated with the rest of the system componentsImplementation of security techniques for tamper resistance, tamper prevention and IP protection mayrequire additional processing power, which is limited in embedded systems. The “processing gap”between the computational requirements of security and the available processing power of embeddedprocessors requires special consideration. Available technologies include use of cryptographic coprocessorsand accelerators, embedded security processors and programmable security protocols. Oneother approach is to develop enhancements in the Instruction Set Architecture (ISA) of embeddedprocessors, in order to efficiently calculate various cryptographic primitives, such us permutations, bitrotations, fast substitutions and modular arithmetic or even build dedicated cryptographic embedded coprocessorswith their own ISA.Even if the “processing gap” is bridged and security functions are provided, embedded systems arerequired to support secure communications as well, considering that, often, embedded applications areimplemented in a distributed environment where communicating systems may exchange (possibly)sensitive data over an untrusted network –wired, wireless or mobile- like Internet, a Virtual PrivateNetwork, the Public Telephone network, etc. In order to fulfil the basic security requirements for securecommunications, embedded systems must be able to use strong cryptographic algorithms and to supportvarious protocols. One of the fundamental requirements regarding secure protocols is interoperability,leading to the requirement for system flexibility and adaptability. Since an embedded system can operatein several environments, e.g. a mobile phone may provide 3G cellular services or connect to a wirelessLAN, it is necessary for the system to operate securely in all environments without loss of performance.Furthermore, as security protocols are developed for various layers of the OSI reference model,embedded systems must be adaptable to different security requirements at each layer of the architecture.Embedded software, such as the operating system or application-specific code, constitutes a crucial factorin secure embedded system design. There are three basic factors that make embedded softwaredevelopment a challenging area of security: (a) complexity of the system, (b) system extensibility and (c)connectivity. Embedded systems serve critical, complex, hard to implement applications with manyparameters that need to be considered, which, in turn, leads to “buggy” and vulnerable software.Furthermore, the required extensibility of conventional embedded systems makes the exploitation ofvulnerabilities relatively easy. Finally, as modern embedded systems are designed with networkconnectivity, the higher the connectivity degree of the system, the higher the risk for a software breach toexpand as time goes by. Many attacks can be implemented by malicious users that exploit softwareglitches and lead to system unavailability, which can have a disastrous impact, e.g. a Denial-of-Serviceattack on a military embedded system.4.2.2.2 Application Design IssuesEmbedded system applications present significant challenges to system designers, in order to achieveefficient and secure systems. A key issue in secure embedded design is user identification and accesscontrol. User identification includes the necessary mechanisms that guarantee that only legitimate usershave access to system resources and can also verify, whenever requested, the identity of the user whohas access to the system. A solution to this problem may come from an emerging new technology for useridentification which is based on biometric recognition, for both user identification and verification.Biometrics are based on pattern recognition in acquired biological data taken from a user who wants togain access to a system, i.e. palm prints, finger prints, iris scan, etc., and comparing them with the datathat have been stored in databases identifying the legitimate users of the system. A secure smart cardwhich uses biometrics capabilities is less vulnerable to attacks when compared to software basedsolutions and that the combination of smartcard and fingerprint recognition is much more robust than PINbasedidentification.PUD2.3.2Issue 5 Page 54 of 122