Showing papers by "Claes-Göran Granqvist published in 2013"

Unconditional Security by the Laws of Classical Physics

Abstract: There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indicates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physically secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnson-noise and a Kirchhoff-loop - i.e., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol - for secure key distribution leads to information theoretic security levels superior to those of today's quantum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer-reviewed publications. The KLJN system is briefly surveyed here with discussions about the essential questions such as (i) perfect and imperfect security characteristics of the key distribution, and (ii) how these two types of securities can be unconditional (or information theoretical).

Bandgap widening in thermochromic Mg-doped VO2 thin films: Quantitative data based on optical absorption

Abstract: Thermochromic Mg-doped VO2 films were deposited by reactive direct current magnetron sputtering onto heated glass and carbon substrates. Elemental compositions were inferred from Rutherford backscattering. Optical bandgaps were obtained from spectral transmittance and reflectance measurements—from both the film side and the back side of the samples—and ensuing determination of absorption coefficients. The bandgap of Mg-doped films was found to increase by 3.9 ± 0.5 eV per unit of atom ratio Mg/(Mg + V) for 0 < Mg/(Mg + V) < 0.21. The presence of ∼0.45 at. % Si enhanced the bandgap even more.

Critical analysis of the Bennett-Riedel attack on secure cryptographic key distributions via the Kirchhoff-Law-Johnson-noise scheme.

Abstract: Recently, Bennett and Riedel (BR) (http://arxiv.org/abs/1303.7435v1) argued that thermodynamics is not essential in the Kirchhoff-law–Johnson-noise (KLJN) classical physical cryptographic exchange method in an effort to disprove the security of the KLJN scheme. They attempted to demonstrate this by introducing a dissipation-free deterministic key exchange method with two batteries and two switches. In the present paper, we first show that BR's scheme is unphysical and that some elements of its assumptions violate basic protocols of secure communication. All our analyses are based on a technically unlimited Eve with infinitely accurate and fast measurements limited only by the laws of physics and statistics. For non-ideal situations and at active (invasive) attacks, the uncertainly principle between measurement duration and statistical errors makes it impossible for Eve to extract the key regardless of the accuracy or speed of her measurements. To show that thermodynamics and noise are essential for the security, we crack the BR system with 100% success via passive attacks, in ten different ways, and demonstrate that the same cracking methods do not function for the KLJN scheme that employs Johnson noise to provide security underpinned by the Second Law of Thermodynamics. We also present a critical analysis of some other claims by BR; for example, we prove that their equations for describing zero security do not apply to the KLJN scheme. Finally we give mathematical security proofs for each BR-attack against the KLJN scheme and conclude that the information theoretic (unconditional) security of the KLJN method has not been successfully challenged.

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Abstract: Reactive dc magnetron sputtering onto glass-based substrates yielded deposits of thermochromic VO2 with well-developed nanorods and nanowires. Their formation was promoted by high substrate temperature (above ∼500 °C), sufficient film thickness, proper inlet of the reactive gas, dispersed gold “seeds,” and pronounced substrate roughness. Rutherford back scattering ascertained mass thicknesses, scanning electron microscopy depicted the nanostructures, and glancing incidence X-ray diffraction proved that single-phase VO2 was normally formed. Spectrophotometric measurements of total and diffuse transmittance and reflectance on VO2 thin films, at room temperature and ∼100 °C, allowed us to determine complex dielectric functions below and above the “critical” temperature for thermochromic switching (∼68 °C). These data were then used in computations based on the Bruggeman effective medium theory applied to randomly oriented prolate spheroidal structural units to derive the optical properties of the deposits. Experimental and computed data on spectral absorptance were found to be in good qualitative agreement.

Nanotechnology in Eco-Efficient Construction

Abstract: Description: As the environmental impact of existing construction and building materials comes under increasing scrutiny, the search for more eco-efficient solutions has intensified. Nanotechnology offers great potential in this area and is already being widely used to great success. Nanotechnology in eco-efficient construction is an authoritative guide to the role of nanotechnology in the development of eco-efficient construction materials and sustainable construction. Following an introduction to the use of nanotechnology in eco-efficient construction materials, part one considers such infrastructural applications as nanoengineered cement-based materials, nanoparticles for high-performance and self-sensing concrete, and the use of nanotechnology to improve the bulk and surface properties of steel for structural applications. Nanoclay-modified asphalt mixtures and safety issues relating to nanomaterials for construction applications are also reviewed before part two goes on to discuss applications for building energy efficiency. Topics explored include thin films and nanostructured coatings, switchable glazing technology and third generation photovoltaic (PV) cells, high-performance thermal insulation materials, and silica nanogel for energy-efficient windows. Finally, photocatalytic applications are the focus of part three, which investigates nanoparticles for pollution control, self-cleaning and photosterilisation, and the role of nanotechnology in manufacturing paints and purifying water for eco-efficient buildings. Nanotechnology in eco-efficient construction is a technical guide for all those involved in the design, production and application of eco-efficient construction materials, including civil engineers, materials scientists, researchers and architects within any field of nanotechnology, eco-efficient materials or the construction industry.-Provides an authoritative guide to the role of nanotechnology in the development of eco-efficient construction materials and sustainable construction-Examines the use of nanotechnology in eco-efficient construction materials-Considers a range of important infrastructural applications, before discussing applications for building energy efficiency Contents: Contributor contact details

Critical analysis of the Bennett-Riedel attack on the secure cryptographic key distributions via the Kirchhoff-law-Johnson-noise scheme

Abstract: Recently, Bennett and Riedel (BR) (http://arxiv.org/abs/1303.7435v1) argued that thermodynamics is not essential in the Kirchhoff-law–Johnson-noise (KLJN) classical physical cryptographic exchange method in an effort to disprove the security of the KLJN scheme. They attempted to demonstrate this by introducing a dissipation-free deterministic key exchange method with two batteries and two switches. In the present paper, we first show that BR’s scheme is unphysical and that some elements of its assumptions violate basic protocols of secure communication. All our analyses are based on a technically-unlimited Eve with infinitely accurate and fast measurements limited only by the laws of physics and statistics. For non-ideal situations and at active (invasive) attacks, the uncertainly principle between measurement duration and statistical errors makes it impossible for Eve to extract the key regardless of the accuracy or speed of her measurements. To show that thermodynamics and noise are essential for the security, we crack the BR system with 100% success via passive attacks, in ten different ways, and demonstrate that the same cracking methods do not function for the KLJN scheme that employs Johnson noise to provide security underpinned by the Second Law of Thermodynamics. We also present a critical analysis of some other claims by BR; for example, we prove that their equations for describing zero security do not apply to the KLJN scheme. Finally we give mathematical security proofs for each BR-attack against the KLJN scheme and conclude that the information theoretic (unconditional) security of the KLJN method has not been successfully challenged.

On the Security of the Kirchhoff-Law-Johnson-Noise (KLJN) Communicator

Abstract: A simple and general proof is given for the information theoretic (unconditional) security of the Kirchhoff-law-Johnson-noise (KLJN) key exchange system under practical conditions. The unconditional security for ideal circumstances, which is based on the Second Law of Thermodynamics, is found to prevail even under slightly non-ideal conditions. This security level is guaranteed by the continuity of functions describing classical physical linear, as well as stable non-linear, systems. Even without privacy amplification, Eve's probability for successful bit-guessing is found to converge towards 0.5 - i.e., the perfect security level - when ideal conditions are approached.

Current and Voltage Based Bit Errors and Their Combined Mitigation for the Kirchhoff-Law–Johnson-Noise Secure Key Exchange

Abstract: We classify and analyze bit errors in the current measurement mode of the Kirchhoff-law–Johnson-noise (KLJN) key distribution. The error probability decays exponentially with increasing bit exchange period and fixed bandwidth, which is similar to the error probability decay in the voltage measurement mode. We also analyze the combination of voltage and current modes for error removal. In this combination method, the error probability is still an exponential function that decays with the duration of the bit exchange period, but it has superior fidelity to the former schemes.

Switchable glazing technology for eco-efficient construction

Abstract: Electrochromic and thermochromic materials and devices make it possible to construct glazings whose throughput of visible light and solar energy can be switched to different levels depending on the application of an electrical voltage or on the temperature, respectively These glazings are of much interest for eco-efficient buildings and are able to impart energy efficiency jointly with indoor comfort The present chapter outlines the basics of the two technologies focusing on functional principles, relevant materials, device and manufacturing technology, as well as selected results from research and development

Does Information Have Mass

Abstract: Does information have mass? This question has been asked many times and there are many answers even on the Internet, including on Yahoo Answers Usually the answer is "no" Attempts have been made to assess the physical mass of information by estimating the mass of electrons feeding the power-guzzling computers and devices making up the Internet, the result being around 50 gram Other efforts to calculate the mass of information have assumed that each electron involved in signal transfer carries one bit of information, which makes the corresponding mass to be about 10^-5 gram We address the fundamental question of minimum mass related to a bit of information from the angles of quantum physics and special relativity Our results indicate that there are different answers depending on the physical situation, and sometimes the mass can even be negative We tend to be skeptical about the earlier mass estimations, mentioned above, because our results indicate that the electron's mass does not play a role in any one of them

On the security of the Kirchhoff-law-Johnson-noise (KLJN) communicator

Abstract: A simple and general proof is given for the information theoretic (unconditional) security of the Kirchhoff-law-Johnson-noise (KLJN) key exchange system under practical conditions. The unconditional security for ideal circumstances, which is based on the Second Law of Thermodynamics, is found to prevail even under slightly non-ideal conditions. This security level is guaranteed by the continuity of functions describing classical physical linear, as well as stable non-linear, systems. Even without privacy amplification, Eve's probability for successful bit-guessing is found to converge towards 0.5 - i.e., the perfect security level - when ideal conditions are approached.

Switchable Glazing Technology: Electrochromic Fenestration for Energy-Efficient Buildings

Abstract: Switchable electrochromic glazings employ multilayer devices with a basic resemblance to thin-film electrical batteries and color/bleach upon electrical charging/discharging. The transmittance of visible light and solar energy can be varied reversibly and persistently between widely separated extrema, which makes it possible to regulate solar energy inflow for energy savings as well as visible light level for comfort reasons. This chapter outlines the basics of electrochromic glazing technology and its implementation in buildings. Device designs and component materials are discussed in some detail. Several practical electrochromic glazing designs are introduced with focus on a foil-type construction applicable as a lamination material between glass panes. Electrochromic glazing has been discussed for many years and has many unfulfilled promises; it is argued here that today’s developments are likely to change this situation so that electrochromic glazing will be able to take its proper place as an important energy savings and comfort enhancing technology for near-zero-energy building refurbishment as well as for new buildings.

Information Theoretic Security by the Laws of Classical Physics

Abstract: It has been shown recently that the use of two pairs of resistors with enhanced Johnson-noise and a Kirchhoff-loop—i.e., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol—for secure key distribution leads to information theoretic security levels superior to those of a quantum key distribution, including a natural immunity against a man-in-the-middle attack. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer-reviewed publications. This presentation first briefly surveys the KLJN system and then discusses related, essential questions such as: what are perfect and imperfect security characteristics of key distribution, and how can these two types of securities be unconditional (or information theoretical)? Finally the presentation contains a live demonstration.

Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange

Abstract: We classify and analyze bit errors in the current measurement mode of the Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability decays exponentially with increasing bit exchange period and fixed bandwidth, which is similar to the error probability decay in the voltage measurement mode. We also analyze the combination of voltage and current modes for error removal. In this combination method, the error probability is still an exponential function that decays with the duration of the bit exchange period, but it has superior fidelity to the former schemes.

Thin Films and Nanostructured Coatings for Eco-Efficient Buildings

Abstract: Thin films and nanostructured coatings are becoming of increasing importance for eco-efficient construction. This chapter discusses the underlying reasons why this is so and then introduces the major technologies. They are subdivided into those requiring vacuum or plasmas – with focus on evaporation and sputtering – and a range of other techniques. Nanoparticle-based coatings are discussed separately, with an emphasis on advanced gas deposition, deposition of carbon-based structures, and microbial fabrication. Large-scale deposition is treated in particular detail, and some views are given on future developments.

Does Information Have Mass

Abstract: Does information have mass? This question has been asked many times and there are many answers even on the Internet, including on Yahoo Answers. Usually the answer is “no”. Attempts have been made to assess the physical mass of information by estimating the mass of electrons feeding the power-guzzling computers and devices making up the Internet, the result being around 50 gram. Other efforts to calculate the mass of information have assumed that each electron involved in signal transfer carries one bit of information, which makes the corresponding mass to be about 10^–5 gram. The difference between the two mass estimates is partially caused by the low energy efficiency of computers. We address the fundamental question of minimum mass related to a bit of information from the angles of quantum physics and special relativity. Our results indicate that there are different answers depending on the physical situation, and sometimes the mass can even be negative. We tend to be skeptical about the earlier mass estimations, mentioned above, because our results indicate that the electron’s mass does not play a role in any one of them.

Ucoditioal security by the laws of classical phy sics 1

Abstract: There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indi cates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physically secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnsonnoise and a Kirchhoff-loop ‒ i.e ., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol ‒ for secure key distribution leads to information theoretic security levels superior to those of today’s quan tum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer- reviewed publications. The KLJN system is briefly surveyed here with discussions about the essential questions such as ( i) perfect and imperfect security characteristics of the key distribution, and ( ii ) how these two types of securities can be unconditional (or information theoretical).