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Power side-channel (PSC) attacks are well-known threats to sensitive hardware like advanced encryption standard (AES) crypto cores. Given the significant impact of supply voltages (VCCs) on power profiles, various countermeasures based on VCC tuning have been proposed, among other defense strategies. Driver strengths of cells, however, have been largely overlooked, despite having direct and significant impact on power profiles as well. For the first time, we thoroughly explore the prospects of jointly tuning driver strengths and VCCs as novel working principle for PSC-attack countermeasures. Toward this end, we take the following steps: 1) we develop a simple circuit-level scheme for tuning; 2) we implement a CAD flow for design-time evaluation of ASICs, enabling security assessment of ICs before tape-out; 3) we implement a correlation power analysis (CPA) framework for thorough and comparative security analysis; 4) we conduct an extensive experimental study of a regular AES design, implemented in ASIC as well as FPGA fabrics, under various tuning scenarios; 5) we summarize design guidelines for secure and efficient joint tuning. In our experiments, we observe that runtime tuning is more effective than static tuning, for both ASIC and FPGA implementations. For the latter, the AES core is rendered >11.8x (i.e., at least 11.8 times) as resilient as the untuned baseline design. Layout overheads can be considered acceptable, with, e.g., around +10% critical-path delay for the most resilient tuning scenario in FPGA. We will release source codes for our methodology, as well as artifacts from the experimental study, post peer-review., Comment: To appear at ISPD'23

The migration of computation to the cloud has raised concerns regarding the security and privacy of sensitive data, as their need to be decrypted before processing, renders them susceptible to potential breaches. Fully Homomorphic Encryption (FHE) serves as a countermeasure to this issue by enabling computation to be executed directly on encrypted data. Nevertheless, the execution of FHE is orders of magnitude slower compared to unencrypted computation, thereby impeding its practicality and adoption. Therefore, enhancing the performance of FHE is crucial for its implementation in real-world scenarios. In this study, we elaborate on our endeavors to design, implement, fabricate, and post-silicon validate CoFHEE, a co-processor for low-level polynomial operations targeting Fully Homomorphic Encryption execution. With a compact design area of $12mm^2$, CoFHEE features ASIC implementations of fundamental polynomial operations, including polynomial addition and subtraction, Hadamard product, and Number Theoretic Transform, which underlie most higher-level FHE primitives. CoFHEE is capable of natively supporting polynomial degrees of up to $n = 2^{14}$ with a coefficient size of 128 bits, and has been fabricated and silicon-verified using 55nm CMOS technology. To evaluate it, we conduct performance and power experiments on our chip, and compare it to state-of-the-art software implementations and other ASIC designs., Comment: 13 pages

Dedicated, after acceptance and publication, in memory of the late Vassos Soteriou. For the first time, we leverage the 2.5D interposer technology to establish system-level security in the face of hardware- and software-centric adversaries. More specifically, we integrate chiplets (i.e., third-party hard intellectual property of complex functionality, like microprocessors) using a security-enforcing interposer. Such hardware organization provides a robust 2.5D root of trust for trustworthy, yet powerful and flexible, computation systems. The security paradigms for our scheme, employed firmly by design and construction, are: 1) stringent physical separation of trusted from untrusted components, and 2) runtime monitoring. The system-level activities of all untrusted commodity chiplets are checked continuously against security policies via physically separated security features. Aside from the security promises, the good economics of outsourced supply chains are still maintained; the system vendor is free to procure chiplets from the open market, while only producing the interposer and assembling the 2.5D system oneself. We showcase our scheme using the Cortex-M0 core and the AHB-Lite bus by ARM, building a secure 64-core system with shared memories. We evaluate our scheme through hardware simulation, considering different threat scenarios. Finally, we devise a physical-design flow for 2.5D systems, based on commercial-grade design tools, to demonstrate and evaluate our 2.5D root of trust., Comment: [v2] Dedicated, after acceptance and publication, in memory of the late Vassos Soteriou. Besides, scaled down some figures for smaller overall file size

Side-channel attacks have empowered bypassing of cryptographic components in circuits. Power side-channel (PSC) attacks have received particular traction, owing to their non-invasiveness and proven effectiveness. Aside from prior art focused on conventional technologies, this is the first work to investigate the emerging Negative Capacitance Transistor (NCFET) technology in the context of PSC attacks. We implement a CAD flow for PSC evaluation at design-time. It leverages industry-standard design tools, while also employing the widely-accepted correlation power analysis (CPA) attack. Using standard-cell libraries based on the 7nm FinFET technology for NCFET and its counterpart CMOS setup, our evaluation reveals that NCFET-based circuits are more resilient to the classical CPA attack, due to the considerable effect of negative capacitance on the switching power. We also demonstrate that the thicker the ferroelectric layer, the higher the resiliency of the NCFET-based circuit, which opens new doors for optimization and trade-offs.

Layout camouflaging can protect the intellectual property of modern circuits. Most prior art, however, incurs excessive layout overheads and necessitates customization of active-device manufacturing processes, i.e., the front-end-of-line (FEOL). As a result, camouflaging has typically been applied selectively, which can ultimately undermine its resilience. Here, we propose a low-cost and generic scheme---full-chip camouflaging can be finally realized without reservations. Our scheme is based on obfuscating the interconnects, i.e., the back-end-of-line (BEOL), through design-time handling for real and dummy wires and vias. To that end, we implement custom, BEOL-centric obfuscation cells, and develop a CAD flow using industrial tools. Our scheme can be applied to any design and technology node without FEOL-level modifications. Considering its BEOL-centric nature, we advocate applying our scheme in conjunction with split manufacturing, to furthermore protect against untrusted fabs. We evaluate our scheme for various designs at the physical, DRC-clean layout level. Our scheme incurs a significantly lower cost than most of the prior art. Notably, for fully camouflaged layouts, we observe average power, performance, and area overheads of 24.96%, 19.06%, and 32.55%, respectively. We conduct a thorough security study addressing the threats (attacks) related to untrustworthy FEOL fabs (proximity attacks) and malicious end-users (SAT-based attacks). An empirical key finding is that only large-scale camouflaging schemes like ours are practically secure against powerful SAT-based attacks. Another key finding is that our scheme hinders both placement- and routing-centric proximity attacks; correct connections are reduced by 7.47X, and complexity is increased by 24.15X, respectively, for such attacks., Comment: arXiv admin note: text overlap with arXiv:1711.05284

Split manufacturing (SM) and layout camouflaging (LC) are two promising techniques to obscure integrated circuits (ICs) from malicious entities during and after manufacturing. While both techniques enable protecting the intellectual property (IP) of ICs, SM can further mitigate the insertion of hardware Trojans (HTs). In this paper, we strive for the "best of both worlds," that is we seek to combine the individual strengths of SM and LC. By jointly extending SM and LC techniques toward 3D integration, an up-and-coming paradigm based on stacking and interconnecting of multiple chips, we establish a modern approach to hardware security. Toward that end, we develop a security-driven CAD and manufacturing flow for 3D ICs in two variations, one for IP protection and one for HT prevention. Essential concepts of that flow are (i) "3D splitting" of the netlist to protect, (ii) obfuscation of the vertical interconnects (i.e., the wiring between stacked chips), and (iii) for HT prevention, a security-driven synthesis stage. We conduct comprehensive experiments on DRC-clean layouts of multi-million-gate DARPA and OpenCores designs (and others). Strengthened by extensive security analysis for both IP protection and HT prevention, we argue that entering the third dimension is eminent for effective and efficient hardware security., Comment: Accepted for IEEE TETC

Leveraging 2.5D interposer technology, we advocate the integration of untrusted commodity components/chiplets with physically separate, entrusted logic components. Such organization provides a modern root of trust for secure system-level integration. We showcase our scheme by utilizing industrial ARM components that are interconnected via a security-providing active interposer, and thoroughly evaluate the achievable security via different threat scenarios. Finally, we provide detailed end-to-end physical design results to demonstrate the efficacy of our proposed methodology.

With the globalization of manufacturing and supply chains, ensuring the security and trustworthiness of ICs has become an urgent challenge. Split manufacturing (SM) and layout camouflaging (LC) are promising techniques to protect the intellectual property (IP) of ICs from malicious entities during and after manufacturing (i.e., from untrusted foundries and reverse-engineering by end-users). In this paper, we strive for "the best of both worlds," that is of SM and LC. To do so, we extend both techniques towards 3D integration, an up-and-coming design and manufacturing paradigm based on stacking and interconnecting of multiple chips/dies/tiers. Initially, we review prior art and their limitations. We also put forward a novel, practical threat model of IP piracy which is in line with the business models of present-day design houses. Next, we discuss how 3D integration is a naturally strong match to combine SM and LC. We propose a security-driven CAD and manufacturing flow for face-to-face (F2F) 3D ICs, along with obfuscation of interconnects. Based on this CAD flow, we conduct comprehensive experiments on DRC-clean layouts. Strengthened by an extensive security analysis (also based on a novel attack to recover obfuscated F2F interconnects), we argue that entering the next, third dimension is eminent for effective and efficient IP protection., Comment: Published in Proc. International Conference On Computer Aided Design (ICCAD) 2018

Split manufacturing (SM) seeks to protect against piracy of intellectual property (IP) in chip designs. Here we propose a scheme to manipulate both placement and routing in an intertwined manner, thereby increasing the resilience of SM layouts. Key stages of our scheme are to (partially) randomize a design, place and route the erroneous netlist, and restore the original design by re-routing the BEOL. Based on state-of-the-art proximity attacks, we demonstrate that our scheme notably excels over the prior art (i.e., 0% correct connection rates). Our scheme induces controllable PPA overheads and lowers commercial cost (the latter by splitting at higher layers)., Comment: Design Automation Conference 2018

Here we advance the protection of split manufacturing (SM)-based layouts through the judicious and well-controlled handling of interconnects. Initially, we explore the cost-security trade-offs of SM, which are limiting its adoption. Aiming to resolve this issue, we propose effective and efficient strategies to lift nets to the BEOL. Towards this end, we design custom "elevating cells" which we also provide to the community. Further, we define and promote a new metric, Percentage of Netlist Recovery (PNR), which can quantify the resilience against gate-level theft of intellectual property (IP) in a manner more meaningful than established metrics. Our extensive experiments show that we outperform the recent protection schemes regarding security. For example, we reduce the correct connection rate to 0\% for commonly considered benchmarks, which is a first in the literature. Besides, we induce reasonably low and controllable overheads on power, performance, and area (PPA). At the same time, we also help to lower the commercial cost incurred by SM., Comment: Published in Proc. Asia South Pac. Des. Autom. Conf. (ASPDAC) 2018

Layout camouflaging (LC) is a promising technique to protect chip design intellectual property (IP) from reverse engineers. Most prior art, however, cannot leverage the full potential of LC due to excessive overheads and/or their limited scope on an FEOL-centric and accordingly customized manufacturing process. If at all, most existing techniques can be reasonably applied only to selected parts of a chip---we argue that such "small-scale or custom camouflaging" will eventually be circumvented, irrespective of the underlying technique. In this work, we propose a novel LC scheme which is low-cost and generic---full-chip LC can finally be realized without any reservation. Our scheme is based on obfuscating the interconnects (BEOL); it can be readily applied to any design without modifications in the device layer (FEOL). Applied with split manufacturing in conjunction, our approach is the first in the literature to cope with both the FEOL fab and the end-user being untrustworthy. We implement and evaluate our primitives at the (DRC-clean) layout level; our scheme incurs significantly lower cost than most of the previous works. When comparing fully camouflaged to original layouts (i.e., for 100% LC), we observe on average power, performance, and area overheads of 12%, 30%, and 48%, respectively. Here we also show empirically that most existing LC techniques (as well as ours) can only provide proper resilience against powerful SAT attacks once at least 50% of the layout is camouflaged---only large-scale LC is practically secure. As indicated, our approach can deliver even 100% LC at acceptable cost. Finally, we also make our flow publicly available, enabling the community to protect their sensitive designs., Comment: Published in Proc. International Conference On Computer Aided Design (ICCAD) 2017; [v2] added DOI to PDF header

Split manufacturing is a promising technique to defend against fab-based malicious activities such as IP piracy, overbuilding, and insertion of hardware Trojans. However, a network flow-based proximity attack, proposed by Wang et al. (DAC'16) [1], has demonstrated that most prior art on split manufacturing is highly vulnerable. Here in this work, we present two practical layout techniques towards secure split manufacturing: (i) gate-level graph coloring and (ii) clustering of same-type gates. Our approach shows promising results against the advanced proximity attack, lowering its success rate by 5.27x, 3.19x, and 1.73x on average compared to the unprotected layouts when splitting at metal layers M1, M2, and M3, respectively. Also, it largely outperforms previous defense efforts; we observe on average 8x higher resilience when compared to representative prior art. At the same time, extensive simulations on ISCAS'85 and MCNC benchmarks reveal that our techniques incur an acceptable layout overhead. Apart from this empirical study, we provide---for the first time---a theoretical framework for quantifying the layout-level resilience against any proximity-induced information leakage. Towards this end, we leverage the notion of mutual information and provide extensive results to validate our model., Comment: Published in Proc. International Conference On Computer Aided Design (ICCAD) 2017; [v2] minor fix Fig 11: avg area overhead for g-type2 was miscalculated; [v3] added DOI to PDF footer