A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Designing Effective Logic Obfuscation: Exploring Beyond Gate-Level Boundaries(2022) Zuzak, Michael Jeffrey; Srivastava, Ankur; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The need for high-end performance and cost savings has driven hardware design houses to outsource integrated circuit (IC) fabrication to untrusted manufacturing facilities. During fabrication, the entire chip design is exposed to these potentially malicious facilities, raising concerns of intellectual property (IP) piracy, reverse engineering, and counterfeiting. This is a major concern of both government and private organizations, especially in the context of military hardware. Logic obfuscation techniques have been proposed to prevent these supply-chain attacks. These techniques lock a chip by inserting additional key logic into combinational blocks of a circuit. The resulting design only exhibits correct functionality when a correct key is applied after fabrication. To date, the majority of obfuscation research centers on evaluating combinational constructions with gate-level criteria. However, this approach ignores critical high-level context, such as the interaction between modules and application error resilience. For this dissertation, we move beyond the traditional gate-level view of logic obfuscation, developing criteria and methodologies to design and evaluate obfuscated circuits for hardware-oriented security guarantees that transcend gate-level boundaries. To begin our work, we characterize the security of obfuscation when viewed in the context of a larger IC and consider how to effectively apply logic obfuscation for security beyond gate-level boundaries. We derive a fundamental trade-off underlying all logic obfuscation that is between security and attack resilience. We then develop an open-source, GEM5-based simulator called ObfusGEM, which evaluates logic obfuscation at the architecture/application-level in processor ICs. Using ObfusGEM, we perform an architectural design space exploration of logic obfuscation in processor ICs. This exploration indicates that current obfuscation schemes cannot simultaneously achieve security and attack resilience goals. Based on the lessons learned from this design space exploration, we explore 2 orthogonal approaches to design ICs with strong security guarantees beyond gate-level boundaries. For the first approach, we consider how logic obfuscation constructions can be modified to overcome the limitations identified in our design space exploration. This approach results in the development of 3 novel obfuscation techniques targeted towards securing 3 distinct applications. The first technique is Trace Logic Locking which enhances existing obfuscation techniques to provably expand the derived trade-off between security and attack resilience. The second technique is Memory Locking which defines an automatable approach to processor design obfuscation through locking the analog timing effects that govern the function of on-chip SRAM arrays. The third technique is High Error Rate Keys which protect probabilistic circuits against a SAT-based attacker by hiding the correct secret key value under stochastic noise. We demonstrate that all 3 techniques are capable of overcoming the limitations of obfuscation when viewed beyond gate-level boundaries in their respective applications. For the second approach, we consider how architectural design decisions can influence hardware security. We begin by exploring security-aware architecture design, an approach where minor architectural modifications are identified and applied to improve security in processor ICs. We then develop resource binding algorithms for high-level synthesis that optimally bind operations onto obfuscated functional units to amplify security guarantees. In both cases, we show that by designing logic obfuscation using architectural context a designer can secure ICs beyond gate-level boundaries despite the presence of the rigid trade-off that rendered prior obfuscation techniques insecure.Item Deep Analysis of Binary Code to Recover Program Structure(2014) ElWazeer, Khaled; Barua, Rajeev; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Reverse engineering binary executable code is gaining more interest in the research community. Agencies as diverse as anti-virus companies, security consultants, code forensics consultants, law-enforcement agencies and national security agencies routinely try to understand binary code. Engineers also often need to debug, optimize or instrument binary code during the software development process. In this dissertation, we present novel techniques to extend the capabilities of existing binary analysis and rewriting tools to be more scalable, handling a larger set of stripped binaries with better and more understandable outputs as well as ensuring correct recovered intermediate representation (IR) from binaries such that any modified or rewritten binaries compiled from this representation work correctly. In the first part of the dissertation, we present techniques to recover accurate function boundaries from stripped executables. Our techniques as opposed to current techniques ensure complete live executable code coverage, high quality recovered code, and functional behavior for most application binaries. We use static and dynamic based techniques to remove as much spurious code as possible in a safe manner that does not hurt code coverage or IR correctness. Next, we present static techniques to recover correct prototypes for the recovered functions. The recovered prototypes include the complete set of all arguments and returns. Our techniques ensure correct behavior of rewritten binaries for both internal and external functions. Finally, we present scalable and precise techniques to recover local variables for every function obtained as well as global and heap variables. Different techniques are represented for floating point stack allocated variables and memory allocated variables. Data type recovery techniques are presented to declare meaningful data types for the detected variables. Our data type recovery techniques can recover integer, pointer, structural and recursive data types. We discuss the correctness of the recovered representation. The evaluation of all the methods proposed is conducted on SecondWrite, a binary rewriting framework developed by our research group. An important metric in the evaluation is to be able to recompile the IR with the recovered information and run it producing the same answer that is produced when running the original executable. Another metric is the analysis time. Some other metrics are proposed to measure the quality of the IR with respect to the IR with source code information available.