Abstract. In order to ensure trusted in-field operation of integrated circuits, it is important to develop efficient low-cost techniques to detect malicious tampering (also referred to as Hardware Trojan) that causes undesired change in functional behavior. Conventional postmanufacturing testing, test generation algorithms and test coverage metrics cannot be readily extended to hardware Trojan detection. In this paper, we propose a test pattern generation technique based on multiple excitation of rare logic conditions at internal nodes. Such a statistical approach maximizes the probability of inserted Trojans getting triggered and detected by logic testing, while drastically reducing the number of vectors compared to a weighted random pattern based test generation. Moreover, the proposed test generation approach can be effective towards increasing the sensitivity of Trojan detection in existing side-channel approaches that monitor the impact of a Trojan circuit on power or current signature. Simulation results for a set of ISCAS benchmarks show that the proposed test generation approach can achieve comparable or better Trojan detection coverage with about 85% reduction in test length on average over random patterns.

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Malicious alterations of integrated circuits during fabrication in untrusted foundries pose major concern in terms of their reliable and trusted field operation. It is extremely difficult to discover such alterations, also referred to as "hardware Trojans" using conventional structural or functional testing strategies. In this paper, we propose a novel non-invasive, multipleparameter side-channel analysis based Trojan detection approach that is capable of detecting malicious hardware modifications in the presence of large process variation induced noise. We exploit the intrinsic relationship between dynamic current (IDDT ) and maximum operating frequency (Fmax) of a circuit to distinguish the effect of a Trojan from process induced fluctuations in IDDT . We propose a vector generation approach for IDDT measurement that can improve the Trojan detection sensitivity for arbitrary Trojan instances. Simulation results with two large circuits, a 32-bit integer execution unit (IEU) and a 128-bit Advanced Encryption System (AES) cipher, show a detection resolution of 0.04% can be achieved in presence of ±20% parameter (V th ) variations. The approach is also validated with experimental results using 120nm FPGA (Xilinx Virtex-II) chips.

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A new approach to software reliability estimation is presented that combines operational testing with stratified sampling in order to reduce the number of program executions that must be checked manually for conformance to requirements. Automatic cluster analysis is applied to execution profiles in order to stratify captured operational executions. Experimental results are reported that suggest this approach can significantly reduce the cost of estimating reliability.

In this paper we present a new test data compression technique andan associated decompression scheme for testing VLSI chips. Our method is based on our novel use of the much utilized in sofinre LZX particularly U 7 7 algorithm. We adapt LZ77 tu accommodate bit strings rather than character sets. Moreover; we exploit the large presence of Don't Cares in the uncompressed test sets that we generated using commercial ATPG tools. Our decompression scheme makes effective use of the on chip boundary scan during decompression and then feeding the internal multiple scan chains for testing. The hardware overhead cost for this scheme is minimal. Experimental results are provided.

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