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Advances in quantum computers may pose a significant threat to existing public-key encryption methods, which are crucial to the current infrastructure of cyber security. Both RSA and ECDSA, the two most widely used security algorithms today, may be (in principle) solved by the Shor algorithm in polynomial time due to its ability to efficiently solve the discrete logarithm problem, potentially making present infrastructures insecure against a quantum attack. The National Institute of Standards and Technology (NIST) reacted with the post-quantum cryptography (PQC) standardization process to develop and optimize a series of post-quantum algorithms (PQAs) based on difficult mathematical problems that are not susceptible to being solved by Shor's algorithm. Whilst high-powered computers can run these PQAs efficiently, further work is needed to investigate and benchmark the performance of these algorithms on lower-powered (constrained) devices and the ease with which they may be integrated into existing protocols such as TLS. This paper provides quantitative benchmark and handshake performance data for the most recently selected PQAs from NIST, tested on a Raspberry Pi 4 device to simulate today's IoT (Internet of Things) devices, and provides quantitative comparisons with previous benchmarking data on a range of constrained systems. CRYSTALS-Kyber and CRYSTALS-Dilithium are shown to be the most efficient PQAs in the key encapsulation and signature algorithms, respectively, with Falcon providing the optimal TLS handshake size. [ABSTRACT FROM AUTHOR]

Traditional and lightweight cryptography primitives and protocols are insecure against quantum attacks. Thus, a real‐time application using traditional or lightweight cryptography primitives and protocols does not ensure full‐proof security. Post‐quantum cryptography is important for the internet of things (IoT) due to its security against quantum attacks. This paper offers a broad literature analysis of post‐quantum cryptography for IoT networks, including the challenges and research directions to adopt in real‐time applications. The work draws focus towards post‐quantum cryptosystems that are useful for resource‐constraint devices. Further, those quantum attacks are surveyed, which may occur over traditional and lightweight cryptographic primitives. [ABSTRACT FROM AUTHOR]

Quantum cryptography achieves a formidable task-the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate quantum networks where devices securely connect to nearby access points or proxy servers. [ABSTRACT FROM AUTHOR]

One of the main open problems in quantum communication is the design of efficient quantum-secured networks. This is a challenging goal, because it requires protocols that guarantee both unconditional security and high communication rates, while increasing the number of users. In this scenario, continuous-variable systems provide an ideal platform where high rates can be achieved by using off-the-shelf optical components. At the same time, the measurement-device independent architecture is also appealing for its feature of removing a substantial portion of practical weaknesses. Driven by these ideas, here we introduce a modular design of continuous-variable network where each individual module is a measurement-device-independent star network. In each module, the users send modulated coherent states to an untrusted relay, creating multipartite secret correlations via a generalized Bell detection. Using one-time pad between different modules, the network users may share a quantum-secure conference key over arbitrary distances at constant rate. The ability of modern society to move towards quantum communications is dependent on the capacity to realize quantum networks with the ability to securely transmit and share information over long distance and among multiple users. The authors propose a protocol for a scalable quantum network made of modules each consisting of continuous-variable measurement-device independent applied to quantum key distribution, allowing to perform secure quantum conferencing among an arbitrary number of users. [ABSTRACT FROM AUTHOR]

One crucial step in any quantum key distribution (QKD) scheme is parameter estimation. In a typical QKD protocol the users have to sacrifice part of their raw data to estimate the parameters of the communication channel as, for example, the error rate. This introduces a trade-off between the secret key rate and the accuracy of parameter estimation in the finite-size regime. Here we show that continuous-variable QKD is not subject to this constraint as the whole raw keys can be used for both parameter estimation and secret key generation, without compromising the security. First, we show that this property holds for measurement-device-independent (MDI) protocols, as a consequence of the fact that in a MDI protocol the correlations between Alice and Bob are postselected by the measurement performed by an untrusted relay. This result is then extended beyond the MDI framework by exploiting the fact that MDI protocols can simulate device-dependent one-way QKD with arbitrarily high precision. [ABSTRACT FROM AUTHOR]

• Experimental and computational description of structure in liquid 5-hydroxymethylfurfural, a sleeping giant among renewable compounds. • Joint X-ray scattering, NMR spectroscopy and Molecular Dynamics reveal heterogeneous structure at atomistic level. • Molecular stacking is detected, driven by π··π interactions. • Strong role of diverse hydrogen bonding in driving local correlations. • The concomitant occurrence of different kinds of interactions leads to an heterogeneous solvation scenario. Here we investigate the local structural organization in liquid neat 5-hydroxymethylfurfural (HMF) by the synergic use of high energy X-ray scattering, NMR spectroscopy and molecular dynamics simulations, providing atomistic insight into the correlations that characterise HMF liquid state. HMF has been acknowledged as one of the "sleeping giants" among those renewable compounds, with yet underexploited market potential. It can be obtained from renewable carbohydrate sources via a few consecutive steps and, due to its different functional groups, it can be potentially transformed into a plethora of compounds. An adequate knowledge of the driving interactions into its liquid state can be of fundamental relevance in individuating successful solvents, where HMF can be dissolved, extracted and treated to deliver new compounds. As such, this study has then the potential to provide new, sustainable routes in HMF manipulation, alternatively to current methods. The X-ray scattering validated MD study reveals the existence of a distinct π–π stacking arrangement, characterising the mutual ordering between neighbour HMF molecules. Further correlations involve hydrogen bonding between aldehyde and hydroxyl oxygen and hydroxyl hydrogen. Furthermore, indication of the existence of OH···π hydrogen bonding interaction has been detected. An NMR strategy has been applied to confirm the existence of these mutual interactions, identifying the associated structural motifs. These findings underscore the complex and heterogeneous nature of the structural organization of liquid HMF. [ABSTRACT FROM AUTHOR]

One-monolayer (ML) (thin) and 5-ML (thick) Si films were grown on the α-phase Si(111)√3 × √3R30°-Bi at a low substrate temperature of 200 °C. Si films have been studied in situ by reflection electron energy loss spectroscopy (REELS) and Auger electron spectroscopy, as a function of the electron beam incidence angle α and low-energy electron diffraction (LEED), as well as ex situ by grazing incidence X-ray diffraction (GIXRD). Scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) were also reported. The REELS spectra, taken at the Si K absorption edge (~1.840 KeV), reveal the presence of two distinct loss structures attributed to transitions 1s→π* and 1s→σ* according to their intensity dependence on α, attesting to the sp2-like hybridization of the silicon valence orbitals in both thin and thick Si films. The synthesis of a silicon allotrope on the α-phase of Si(111)√3 × √3R30°-Bi substrate was demonstrated by LEED patterns and GIXRD that discloses the presence of a Si stack of 3.099 (3) Å and a √3 × √3 unit cell of 6.474 Å, typically seen for multilayer silicene. STM and STS measurements corroborated the findings. These measurements provided a platform for the new √3 × √3R30° Si allotrope on a Si(111)√3 × √3 R30°-Bi template, paving the way for realizing topological insulator heterostructures from different two-dimensional materials, Bi and Si. [ABSTRACT FROM AUTHOR]

We report on the electronic properties of straight, 1.6 nm wide, silicene nanoribbons on Ag(110), arranged in a one-dimensional grating with a pitch of 2 nm, whose high-resolution scanning tunneling microscopy images reveal a honeycomb geometry. Angle-resolved photoemission shows quantum confined electronic states of one-dimensional character. The silicon band dispersion along the direction of the nanoribbons suggests a behavior analogous to the Dirac cones of graphene on different substrates. [ABSTRACT FROM AUTHOR]

• Chemical physical and structural characterization of a large family of symmetric dialkyl carbonates (DACs). • Development of MD simulation interatomic potential for the compound family. • Nature of the structural organization in DACs: role of hydrogen bonding and mesoscopic segregation. Dialkyl carbonates (DAC) with short-medium alkyl length - oleochemical carbonates – are attracting attention because of their appealing properties, including low viscosity, flammability, toxicity, environmental impact and wide range of applications: lubricants, personal care, fuel additives etc. However, not much is known concerning their chemical physical properties and, more importantly, on the nature of microscopic correlations that eventually determine bulk performances. In view of this paucity, we present a large exploration of a series of chemical physical properties of a set of DACs ranging from dimethyl up to didodecyl carbonate. This study extends previously determined databases, thus providing a complete picture of the temperature dependence of chemical physical properties around room temperature. Furthermore, we explored the microscopic morphology of DACs, by synergic exploitation of X-ray scattering and Molecular Dynamics techniques. These tools allow detecting the existence of a distinct degree of mesoscopic spatial segregation between polar carbonate moieties and apolar alkyl chains domains. The role of first neighbour carbonate moieties in driving the corresponding molecules towards weak hydrogen bonding interactions and alkyl chain alignment is described. Such an effect is related to the overall mesoscopic segregation of alkyl tails that isolate small droplets formed by stacked carbonate groups. Such a highly compartmentalised morphology can explain and potentially suggest applications of DACs in fields as relevant as separation, catalysis, lubrication etc. [ABSTRACT FROM AUTHOR]

We report new findings on multilayer silicene grown on Si(111)√3 × √3 R30°–Ag template, after the recent first compelling experimental evidence of its synthesis. Low-energy electron diffraction, reflection high-energy electron diffraction, and energy-dispersive grazing incidence X-ray diffraction measurements were performed to show up the fingerprints of √3 × √3 multilayer silicene. Angle-resolved photoemission spectroscopy displayed new features in the second surface Brillouin zone, attributed to the multilayer silicene on Si(111)√3 × √3 R30°–Ag. Band-structure dispersion theoretical calculations performed on a model of three honeycomb stacked layers, silicene grown on Si(111)√3 × √3 R30°-Ag surface confirm the experimental results. [ABSTRACT FROM AUTHOR]

Multilayer silicene, the silicon analogue of multilayer graphene, grown on silver (111) surfaces, possesses a honeycomb ([Square_Root]3 × [Square_Root]3)R30° reconstruction, observed by scanning tunnelling microscopy at room temperature, past the initial formation of the dominant, 3×3 reconstructed, silicene monolayer. For a few layers silicene film we measure by synchrotron radiation photoelectron spectroscopy, a cone-like dispersion at the Brillouin zone centre due to band folding. π* and π states meet at ∼0.25 eV below the Fermi level, providing clear evidence of the presence of gapless Dirac fermions. [ABSTRACT FROM AUTHOR]