Publications

Advanced, superscalar microprocessors (μP) are highly susceptible to wear-out failures because of their highly complex, densely packed circuit structure and extreme operational frequencies. Although many types of fault detection and mitigation strategies have been proposed, none have addressed the specific problem of detecting faults that lead to information leakage events on I/O channels of the μP. Information leakage can be defined very generally as any type of output that the executing program did not intend to produce. In this work, we restrict this definition to output that represents a security concern, and in particular, to the leakage of plaintext or encryption keys, and propose a counter-based countermeasure to detect faults that cause this type of leakage event. Fault injection (FI) experiments are carried out on two RISC-V microprocessors emulated as soft cores on a Xilinx multi-processor System-on-chip (MPSoC) FPGA. The μP designs are instrumented with a set of counters that records the number of transitions that occur on internal nodes. The transition counts are collected from all internal nodes under both fault-free and faulty conditions, and are analyzed to determine which counters provide the highest fault coverage and lowest latency for detecting leakage faults. We show that complete coverage of all leakage faults is possible using only a single counter strategically placed within the branch compare logic of the μPs.

The RISC-V instruction set architecture open licensing policy has spawned a hive of development activity, making a range of implementations publicly available. The environments in which RISC-V operates have expanded correspondingly, driving the need for a generalized approach to evaluating the reliability of RISC-V implementations under adverse operating conditions or after normal wear-out periods. Fault injection (FI) refers to the process of changing the state of registers or wires, either permanently or momentarily, and then observing execution behavior. The analysis provides insight into the development of countermeasures that protect against the leakage or corruption of sensitive information, which might occur because of unexpected execution behavior. In this article, we develop a hardware-software co-design architecture that enables fast, configurable fault emulation and utilize it for information leakage and data corruption analysis. Modern system-on-chip FPGAs enable building an evaluation platform, where control elements run on a processor(s) (PS) simultaneously with the target design running in the programmable logic (PL). Software components of the FI system introduce faults and report execution behavior. A pair of RISC-V FI-instrumented implementations are created and configured to execute the Advanced Encryption Standard and Twister algorithms. Key and plaintext information leakage and degraded pseudorandom sequences are both observed in the output for a subset of the emulated faults.

While public-key cryptography is essential for secure communications, the energy cost of even the most efficient algorithms based on Elliptic Curve Cryptography (ECC) is prohibitive on many ultra-low energy devices such as sensornetwork nodes and identification tags. Although an abundance of hardware acceleration techniques for ECC have been proposed in literature, little research has focused on understanding the energy benefits of these techniques. Therefore, we evaluate the energy cost of ECC on several different hardware/software configurations across a range of security levels. Our work comprehensively explores implementations of both GF(p) and GF(2m) ECC, demonstrating that GF(2m) provides a 1.31 to 2.11 factor improvement in energy efficiency over GF(p) on an extended RISC processor. We also show that including a 4KB instruction cache in our system can reduce the energy cost of ECC by as much as 30%. Furthermore, our GF(2m) coprocessor achieves a 2.8 to 3.61 factor improvement in energy efficiency compared to instruction set extensions and significantly outperforms prior work.

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Abstract not provided.