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Modern VLSI designs incorporate a high amount of instrumentation that supports post-silicon validation and debug, volume test and diagnosis, as well as in-field system monitoring and maintenance. Reconfigurable scan architectures, as allowed by the novel IEEE Std 1149.1-2013 (JTAG) and IEEE Std 1687-2014 (IJTAG), emerge as a scalable mechanism for access to such on-chip instruments.While the on-chip instrumentation is crucial for meeting quality, dependability, and time-to-market goals, it is prone to abuse and threatens system safety and security. A secure access management method is mandatory to assure that critical instruments be accessible to authorized entities only.This work presents a novel protection method for fine-grained access management in complex reconfigurable scan networks based on a challenge-response authentication protocol. The target scan network is extended with an authorization instrument and Secure Segment Insertion Bits (S 2 IB) that together control the accessibility of individual instruments. To the best of the authors' knowledge, this is the first fine-grained access management scheme that scales well with the number of protected instruments and offers a high level of security. Compared with recent stateof-the-art techniques, this scheme is more favorable with respect to implementation cost, performance overhead, and provided security level.Index Terms-Debug and diagnosis, reconfigurable scan network, IJTAG, IEEE Std 1687, secure DFT, hardware security, instrument protection 0278-0070 (c)

Fault simulation is an essential tool in electronic design automation. The accuracy of the computation of fault coverage in classic n-valued simulation algorithms is compromised by unknown (X) values. This results in a pessimistic underestimation of the coverage, and overestimation of unknown (X) values at the primary and pseudo-primary outputs. This work proposes the first stuck-at fault simulation algorithm free of any simulation pessimism in presence of unknowns. The SAT-based algorithm exactly classifies any fault and distinguishes between definite and possible detects. The pessimism w. r. t. unknowns present in classic algorithms is discussed in the experimental results on ISCAS benchmark and industrial circuits. The applicability of our algorithm to large industrial circuits is demonstrated. Preprint General Copyright NoticeThis article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. This is the author's "personal copy" of the final, accepted version of the paper published by IEEE. Abstract-Fault simulation is an essential tool in electronic design automation. The accuracy of the computation of fault coverage in classic n-valued simulation algorithms is compromised by unknown (X) values. This results in a pessimistic underestimation of the coverage, and overestimation of unknown (X) values at the primary and pseudo-primary outputs.This work proposes the first stuck-at fault simulation algorithm free of any simulation pessimism in presence of unknowns. The SAT-based algorithm exactly classifies any fault and distinguishes between definite and possible detects.The pessimism w. r. t. unknowns present in classic algorithms is discussed in the experimental results on ISCAS benchmark and industrial circuits. The applicability of our algorithm to large industrial circuits is demonstrated.