Architectures and Design Methodologies for Micro and Nanocomputing

For many years, the transistors placement was not limited by interconnections thanks to the Digital Integrated Circuits market that is changing from a situation where CMOS technology was the reference (microelectronics era) to a plurality of emerging technologies (nanoelectronics era). The costs of optics photolithography needed to produce the recent CMOS technologies are increasing to such an extent as to make interesting the exploration of nanoelectronics alternative solutions. These technologies are called beyond CMOS technologies. Among the application fields, Information Security is one of the most pioneering rising market: several application areas need to ensure confidentiality and authenticity of data through cryptographic solutions. In some cases, cryptographic primitives can benefit a strong hardware acceleration. Unfortunately, CMOS based systems are vulnerable to ageing factors, such as Electromigration which decreases the reliability of certain security properties, and to Side-Channel attacks, where an attacker can retrieve confidential information by observing the power consumption. In this scenario, it is possible to speculate that emerging nanotechnologies can be exploited to cover the gaps left uncovered by CMOS technologies. A sub-class of circuits based on this novel techno- logical approach are called Dynamically-Coupled Systems (DCS). These novel technologies go beyond the transistor-interconnection dichotomy: elaboration, storage and transmission functions are all performed by the same device. DCS building blocks are called Processing Elements (PE). Interconnections are replaced with PE chains that are intrinsically pipelined. Ideally, it is possible to divide DCS technologies in two conventional sub-classes: Electrical-Coupled Technologies (ECT) where information propagation is due to electrons flow across ohmic paths and Field-Coupled Technologies (FCT). In FCT both the propagation and the elaboration of data depends on the electromagnetic field in- teractions (coupling) among PEs. An interesting possibility is offered by the use of single domain nanomagnets. Rectangular shaped magnets, with sizes smaller than 100nm, demonstrate a bistable behavior. This principle has been exploited to design digital logic circuits, leading to the so-called NanoMagnet Logic. The energy landscape of a single domain nanomagnet has two minimums corresponding to the magnetization vector aligned along the longer magnet side. If an ideal magnet is forced in the metastable state (i.e. the peak in the energy landscape), the probability that the magnet will reach one of the two stable states is exactly 0.5. The presented work proposes a plurality of development environments employable to study and design Dynamical-Coupled Nanocomputing digital circuits based on both a bottom-up approach for “fast prototyping” and a top-down one for complex circuits development environment. By means of the presented tools, it has been possible to study a series of Arithmetic and Cryptographic architectures, to perform circuit performance analysis and to highlight how the Modular Arithmetic offers a substantial contribution to the Field-Coupled Nanotechnologies interconnections overhead issue.