Memristive technologies can enable novel mixed-mode (MM) circuit architectures, where diverse stateful and non-stateful logic operations are executed by the same physical device. Recently introduced optimal synthesis procedures for MM circuits have achieved 3-5X area and latency improvements compared with single-mode memristive logic families, yet such methods are not scalable. In this paper, we present a synthesis approach for MM circuits that leverages synthesis techniques for majority-inverter graphs (MIGs). MIG vertices are natural descriptions of non-stateful voltage-input (V-op) and stateful resistance-input (R-op) logic operations. Our synthesis can handle circuits with up to 27 inputs and achieves an average reduction of 80% in required devices and 65% delay when compared to a state-of-the-art approach for R-ops.

Memristive crossbars are attractive for in-memory computing due to their integration density combined with compute and storage capabilities of their basic devices. However, yield and fidelity of emerging memristive technologies can make their reliable operation unattainable, thus raising interest in simpler topologies. In this paper, we consider synthesis of Boolean functions on 1D memristive line arrays. We propose an optimal procedure that can fully utilize the rich electrical behavior of memristive devices, mixing stateful (resistance-input) and non-stateful (voltage-input) operations as desired by the designer, leveraging their respective strengths. The synthesis method is based on Boolean satisfiability (SAT) solving and supports flexible constraints to enforce, e.g., restrictions of the available peripher-als. We experimentally validate memristive logic circuits beyond individual logic gates by demonstrating the operation of a Galois field multiplier using a 1D line array of 10 memristors in parallel, highlighting the robust performance of our proposed mixed-mode circuit and its synthesis procedure.

Memristive devices can not only be used as nonvolatile memories but also enable computation-in-memory (CIM) computing paradigms. CIM architectures show prospects in significantly reducing the data interaction time and energy consumption between processors and storage, thus addressing the bottleneck problem of the von Neumann architecture. Additionally, the capability of memristive devices to store multiple (resistance) states in one cell offer vast potential for CIM’s multi-valued logic, as they greatly enhance data storage density and computational efficiency. In this study, a novel concept for ternary Łukasiewicz logic utilizing the voltage divider of two (anti-)serially connected memristive devices is proposed. As this approach does not require any switching in the computation process and features a straightforward circuit architecture, a low energy consumption per operation is achieved. In addition, the concept is crossbar-array compatible. The concept is validated by circuit simulations using the JART VCM v1b model that has been calibrated to experimental data of a Pt/Ta2O5/W memristive device.

The execution of deep neural network (DNN) algorithms suffers from significant bottlenecks due to the separation of the processing and memory units in traditional computer systems. Emerging memristive computing systems introduce an in situ approach that overcomes this bottleneck. The nonvolatility of memristive devices, however, may expose the DNN weights stored in memristive crossbars to potential theft attacks. Therefore, this article proposes a 2-D permutation-based protection (TDPP) method that thwarts such attacks. We first introduce the underlying concept that motivates the TDPP method: permuting both the rows and columns of the DNN weight matrices. This contrasts with previous methods, which focused solely on permuting a single dimension of the weight matrices, either the rows or columns. While it is possible for an adversary to access the matrix values, the original arrangement of rows and columns in the matrices remains concealed. As a result, the extracted DNN model from the accessed matrix values would fail to operate correctly. We consider two different memristive computing systems (designed for layer-by-layer and layer-parallel processing, respectively), and demonstrate the design of the TDPP method that could be embedded into the two systems. Finally, we present a security analysis. Our experiments demonstrate that TDPP can achieve comparable effectiveness to prior approaches, with a high level of security when appropriately parameterized. In addition, TDPP is more scalable than previous methods and results in reduced area and power overheads. The area and power are reduced by, respectively,$1218\times $and$2815\times $for the layer-by-layer system and by$178\times $and$203\times $for the layer-parallel system compared to prior works.

Quick progress in memristive technologies has led to their consideration for several potential applications, many of which are security-critical. New possibilities of memristors, including their unique combination of non-volatile storage and compute capabilities, make them particularly attractive to edge applications, which are physically exposed to their users and therefore to potential attackers. Therefore, practical deployment of memristive circuitry for, e.g., cryptographic (sub-)modules or on-chip neural network inference, is only feasible when their vulnerability to physical attacks is understood and addressed. We evaluate experimentally one relevant class of physical attacks, namely side-channel attacks, under varying external conditions, namely temperature and magnetic fields. Using a small cryptographic construction, we evaluate both white-box and black-box attack varieties, using respective cryptanalytic techniques. Our results show that, while non-nominal conditions can complicate attacks, the information leakage remains and the secrets are extractable with additional knowledge about the memristive devices. This suggests the need to consider possible external disturbances during security evaluation.

Memristive technologies offer fascinating opportunities for unconventional computing architectures and emerging applications. While memristive devices have received substantial attention as sources of entropy for security applications, security vulnerabilities of memristive technologies for implementing cryptographic circuits have been largely neglected so far. In this article, we provide the first in-depth analysis of power side-channel analysis against memristive cryptographic implementations based on both: physical experiments and simulations. We show that power consumption models developed for CMOS are not fully adequate for memristive circuits. In particular, the memory effect makes even input-independent initialization cycles vulnerable to attacks that would be fundamentally impossible in CMOS technologies. We propose a memristive-oriented Power Estimation Model (mPEM) integrated into the Stochastic Approach (StA) framework and demonstrate its effectiveness against larger-scale circuits. Finally, we demonstrate that attack countermeasures that were effective for CMOS fail for fundamental reasons in the memristive case.

The field of computer hardware stands at the verge of a revolution driven by recent breakthroughs in emerging nanodevices. “Nano Security” is a new Priority Program recently approved by DFG, the German Research Council. This initial-stage project initiative at the crossroads of nano-electronics and hardware-oriented security includes 11 projects with a total of 23 Principal Investigators from 18 German institutions. It considers the interplay between security and nano-electronics, focusing on a dichotomy which emerging nano-devices (and their architectural implications) have on system security. The projects within the Priority Program consider both: potential security threats and vulnerabilities stemming from novel nano-electronics, and innovative approaches to establishing and improving system security based on nano-electronics. This paper provides an overview of the Priority Program's overall philosophy and discusses the scientific objectives of its individual projects.

Breakthroughs in Deep neural networks (DNNs) steadily bring new innovations that substantially improve our daily life. However, DNNs overwhelm our existing computer architectures because the latter is largely bottlenecked by the data movement between memory and processing units. As a matter of fact, in the current von-Neumann architecture, which has remained unchanged since the beginning, data repeatedly moves back and forth between the physically-separated processing units (e.g., CPU, accelerator, etc.) and memory. This, in turn, inevitably leads to large latency and efficiency losses. In DNNs such a bottleneck becomes more and more prominent due to the massive amount of data that must be frequently transferred. This paper provides a cross-layer overview on how post-von-Neumann in-memory computing (IMC) architectures can be realized using three different emerging technologies: Charge-based ferroelectric transistors for logic-in-memory computations; memristive devices for unconventional brain-inspired computing; and ultra-low-power memristors especially suitable for Edge AI. Various levels of abstraction will be covered starting from semiconductor device physics to circuit and microarchitecture levels all the way up to the system level, but special attention will be put on reliability aspects.

This paper proposes a novel BiFeO3memristor-based electronic circuit for the encryption of sensitive medical data. The hardware cryptographic system is tested through the use of neural signals from a patient experiencing a number of focal epileptic seizures. The Cellular Nonlinear Network theoretical framework provides a basis for sophisticated neural signal processing techniques capable to anticipate the emergence of an epileptic seizure in many cases. The application of these techniques to original data successfully reveals changes before the onset of each epileptic seizure. This information may not be extracted from the encoded data, validating the proper functioning of the memristor-based encryption.

Memristive devices have recently been proposed as efficient implementations of plastic synapses in neuromorphic systems. The plasticity in these memristive devices, i.e. their resistance change, is defined by the applied waveforms. This behavior resembles biological synapses, whose plasticity is also triggered by mechanisms that are determined by local waveforms. However, learning in memristive devices has so far been approached mostly on a pragmatic technological level. The focus seems to be on finding any waveform that achieves spike-timing-dependent plasticity (STDP), without regard to the biological veracity of said waveforms or to further important forms of plasticity. Bridging this gap, we make use of a plasticity model driven by neuron waveforms that explains a large number of experimental observations and adapt it to the characteristics of the recently introduced BiFeO$_3$ memristive material. Based on this approach, we show STDP for the first time for this material, with learning window replication superior to previous memristor-based STDP implementations. We also demonstrate in measurements that it is possible to overlay short and long term plasticity at a memristive device in the form of the well-known triplet plasticity. To the best of our knowledge, this is the first implementations of triplet plasticity on any physical memristive device.