Blockchain Papers

Yasminar Amaerita Telaumbanua

Writing skripsi is an obligatory scientific work for students at the last semester at English education study program of IKIP Gunungsitoli. It is done through a research. The research is conducted based on a certain research design. Teacher-researcher did a research to describe what article errors done by the students, how many times the students are writing article errors and why the students cannot revise the article errors successfully particularly in Chapter I. The data source was from the three skripsi done by three students who graduated faster, 3 years and half. As the research findings, the teacher-researcher found there were three kinds of article errors done by the three students in their skripsi in Chapter I namely indefinite article (a, an), definite article (the) and zero article. It’s concluded that the article errors which were done by the three students who wrote their skripsi are indefinite articles (a, an), definite article (the) and zero article, the three students write article errors as 34 times of 27 sentences and the three students cannot revise the article errors successfully because lack of knowledge of using articles as well as lack of attention to find out proof readers to make better papers.

Lihua Song, Xinran Ju, Zongke Zhu, Mengchen Li

Abstract Information security has become the focus problem in the Internet of Things, and the traditional centralized access control model is faced with threats such as single point failure, internal attack, and central leak. In this paper, we proposed a model to improve the access control security of the Internet of Things, which is based on zero-knowledge proof and smart contract technology in the blockchain. Firstly, we deployed the attribute information of access control in the blockchain, which relieves the pressure and credibility problem brought by the third-party information concentration; Secondly, the encrypted access control token is used to gain the access permission of the resources, which makes the user's identity invisible and effectively avoids the attribute ownership exposure problem; Besides, the use of smart contracts solves the problem of low computing efficiency of Internet of Things devices and the waste of blockchain computing power resources; Finally, a prototype of Internet of Things access control system based on blockchain and zero-knowledge proof technology is implemented. The test analysis results show that the model achieves effective attribute privacy protection, compared with the Attribute-Based Access Control model of the same security level, the access efficiency increases linearly with the increase of access scale.

顺东 LI, 文丽 WANG, 润萌 DU

Secure multiparty computation is a focus of the international cryptographic community. The millionaires problem is the most important problem in secure multiparty computation and is a building block for constructing other secure multiparty computation protocols. Several solutions are available to solve this problem, but except for protocols based on garbled circuits, the existing solutions based on public key cryptosystems are only secure in semihonest models. No solution based on a public key cryptosystem is secure against malicious adversaries. This state restricts the resolution of many secure multiparty computation problems in malicious scenarios. A solution that is secure in malicious models is highly applicable in practical application scenarios and is generally appealing. Therefore, the study of the solution to the millionaires problem in a malicious model is of great theoretical and practical significance. In this work, we propose a multiparty computation protocol for the millionaires problem that is secure in a semihonest model. The proposed protocol is simple and easily understandable. We analyze the possible malicious behaviors in this protocol and use zero-knowledge proof and cut-and-choose techniques to resist possible malicious behaviors and thereby convert the protocol into one that is secure in the malicious model. We prove that the proposed protocol is secure in the malicious model by using the well-accepted ideal-real paradigm. Theoretical efficiency analysis shows that the efficiency of our protocol is at least six times that of existing protocols.

Takeshi Miyamae, K. Matsuura

In blockchain-based anonymous cryptocurrencies, due to their tamper-resistance and transparency characteristics, transaction data are initially required to be anonymous, with the help of various cryptographic techniques, e.g., commitment schemes and zero-knowledge proofs. Also, cryptocurrencies are different from existing anonymous messaging protocols regarding the software architecture and the underlying security model. Due to these differences, the sense of anonymity must be specifically defined for anonymous cryptocurrencies, and the anonymity in each anonymous cryptocurrency must be analyzed and evaluated based on the specific architecture model. In this paper, we first propose a specific architecture model with three software layers to anonymous cryptocurrencies. Next, we introduce definitions of fundamental privacy properties (Pfitzmann's anonymity, unlinkability, and pseudonymity) and comprehensively analyze each privacy property for each architecture layer of anonymous cryptocurrencies to establish a privacy evaluation policy for anonymous cryptocurrencies. Finally, we fairly compare the privacy of current leading anonymous cryptocurrencies (e.g., Zerocash, CryptoNote, and Mimblewimble) using the privacy evaluation policy.

Pouriya Alikhani, Nicolas Brunner, Claude Crépeau, Sébastien Designolle · 8 authors

Protecting secrets is a key challenge in our contemporary information-based era. In common situations, however, revealing secrets appears unavoidable, for instance, when identifying oneself in a bank to retrieve money. In turn, this may have highly undesirable consequences in the unlikely, yet not unrealistic, case where the bank's security gets compromised. This naturally raises the question of whether disclosing secrets is fundamentally necessary for identifying oneself, or more generally for proving a statement to be correct. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances ($\geqslant$400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain applications such as cryptocurrencies or smart contracts.

Sabater, César, Bellet, Aurélien, Ramon, Jan

Learning from data owned by several parties, as in federated learning, raises challenges regarding the privacy guarantees provided to participants and the correctness of the computation in the presence of malicious parties. We tackle these challenges in the context of distributed averaging, an essential building block of distributed and federated learning. Our first contribution is a novel distributed differentially private protocol which naturally scales with the number of parties. The key idea underlying our protocol is to exchange correlated Gaussian noise along the edges of a network graph, complemented by independent noise added by each party. We analyze the differential privacy guarantees of our protocol and the impact of the graph topology, showing that we can match the accuracy of the trusted curator model even when each party communicates with only a logarithmic number of other parties chosen at random. This is in contrast with protocols in the local model of privacy (with lower accuracy) or based on secure aggregation (where all pairs of users need to exchange messages). Our second contribution is to enable users to prove the correctness of their computations without compromising the efficiency and privacy guarantees of the protocol. Our construction relies on standard cryptographic primitives like commitment schemes and zero knowledge proofs.

Oluwatobiloba Ololade

The quick jumps in developing new digital identity technologies have resulted in this trend of developing privacy-preserving solutions in Know Your Customer (KYC) verification systems. This article delves into the evolution of an Advanced Digital Identity Orchestration Engine to enhance privacy protection in the KYC processes. With the rise of concerns surrounding data privacy and security, traditional knowledge of customer systems which are based on centralized database, have faced major challenges including data breaches and unauthorized access. In contrast, the proposed identity orchestration engine draws on the use of Self-Sovereign Identity (SSI) principles, blockchain technology, and verifiable credentials to offer a decentralized, secure and privacy-preserving solution to identity management problem. This engine allows users to manage their personal identity information, and selectively share their information with entities they trust without losing their privacy. By leveraging decentralized identifiers (DIDs) and public key cryptography, the system is enabled to ensure the sensitive data isn't kept in a central place causing reduction in the odds of unauthorized access. Furthermore, features such as zero knowledge proofs (ZKPs) and selective disclosure provide the option for a granular control on what data is shared to ensure that only the required information is provided to comply with regulation requirements. This article also talks about integrating the orchestration engine with existing frameworks for KYC and explores the scalability, interoperability, and potential for this engine to help increase inclusivity in digital identity management. Through case studies and real-world examples, the paper points out the efficiency in working of this engine in getting better security and privacy and user experience in the process of KYC verification. Ultimately, the solution proposed creates a major step forward to privacy-preserving and user-centric digital Identity systems adapted both globally to regulatory requirements and to increase trust in digital financial services.

Prabhanjan Ananth, Kai-Min Chung, Rolando L. La Placa

We study the notion of zero-knowledge secure against quantum polynomial-time verifiers (referred to as quantum zero-knowledge) in the concurrent composition setting. Despite being extensively studied in the classical setting, concurrent composition in the quantum setting has hardly been studied. We initiate a formal study of concurrent quantum zero-knowledge. Our results are as follows: -Bounded Concurrent QZK for NP and QMA: Assuming post-quantum one-way functions, there exists a quantum zero-knowledge proof system for NP in the bounded concurrent setting. In this setting, we fix a priori the number of verifiers that can simultaneously interact with the prover. Under the same assumption, we also show that there exists a quantum zero-knowledge proof system for QMA in the bounded concurrency setting. -Quantum Proofs of Knowledge: Assuming quantum hardness of learning with errors (QLWE), there exists a bounded concurrent zero-knowledge proof system for NP satisfying quantum proof of knowledge property. Our extraction mechanism simultaneously allows for extraction probability to be negligibly close to acceptance probability (extractability) and also ensures that the prover's state after extraction is statistically close to the prover's state after interacting with the verifier (simulatability). The seminal work of [Unruh EUROCRYPT'12], and all its followups, satisfied a weaker version of extractability property and moreover, did not achieve simulatability. Our result yields a proof of quantum knowledge system for QMA with better parameters than prior works.

Alexander Maletzky

No abstract is available for this record.

Xiu‐Shuang Xing, Cai Sun, Lu Liu, Ming‐Sheng Wang · 5 authors

Open AccessCCS ChemistryRESEARCH ARTICLE1 Nov 2021Light-Responsive Proton Conductor: Record High Gain of Proton Conductivity Achieved by Photoinduced Electron-Transfer Strategy Xiu-Shuang Xing†, Cai Sun†, Lu Liu, Ming-Sheng Wang and Guo-Cong Guo Xiu-Shuang Xing† State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Henan Key Laboratory of New Optoelectronic Functional Materials, College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455000 †X.-S. Xing and C. Sun contributed equally to this work.Google Scholar More articles by this author , Cai Sun† State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, Fujian 350108 Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108 †X.-S. Xing and C. Sun contributed equally to this work.Google Scholar More articles by this author , Lu Liu State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Google Scholar More articles by this author , Ming-Sheng Wang *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108 Google Scholar More articles by this author and Guo-Cong Guo State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.021.202000610 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Light-responsive proton conductors might find applications in both traditional fields (fuel cells, chemical sensors, bio-ionic functions, etc.) and modern high-speed switchable smart systems (Internet of things, robotics, etc.). Previous synthetic methods resulted in low switching contrasts (<two times) or they tended to be limited significantly in solid matrixes due to large structural changes. The photoinduced electron-transfer (PIET) method avoids the influence of stereo space in solid matrixes and capable of achieving high switching contrasts. For the first time, we applied the PIET strategy to design light-responsive proton conductors to achieve the hitherto largest gain of proton conductivity (ca. 54 times) for light-responsive proton conductors in one crystalline photochromic viologen-based H-bonded supramolecule. The weakening of hydrogen-bonding interactions in the proton-transport path after PIET accounted for an increased proton conductivity. These findings would inspire the exploration of photon conductors that display higher proton conductivities or switchable smart systems with high contrasts. Download figure Download PowerPoint Introduction Proton conductors attract extensive attention for applications in fuel cells, chemical sensors, and bio-ionic functions.1–3 Current research endeavors mainly focus on achieving high conductivity in crystalline materials with H-bonded networks such as coordination polymers (CPs) and metal–organic frameworks (MOFs) by encapsulation of proton carriers, pore surface functionalization, defect introduction, and so on.4–12 However, due to the development and stimulation of high-tech industries such as the Internet of things and robotics, regular proton conductors cannot meet the new stimuli-responsive smart systems’ requirements. The light mode has advantages of noninvasiveness, high spatial resolution, and easy and quick modulation, and thus, light-responsive proton conductors and related systems have attracted close attention. For example, Wen et al.13 fabricated a bio-inspired photoelectric conversion system based on a cross-membrane pump of proton originating from the light-driven dissociation of a photoacid; the Kitagawa group14 provided a photoacid (pyranine)-doping strategy to increase mobile acidic protons and local defects upon irradiation, and thus, realized the enhancement of proton conductivity (contrast: ca. one time) in a melted CP. Additionally, the Heinke group observed a photoinduced decrease of proton conductivity due to an enhancement of hydrogen-bonding interactions between framework and proton-conducting guests when photochromic azobenzene (contrast: ca. one time)15 or spiropyran (contrast: ca. 100 times)16 moieties were anchored to the linker of a MOF. Further, very recently, Chen’s group17 achieved a dramatic decrease in proton conductivity (contrast: ca. 10,000 times) by encapsulating sulfonated spiropyran into MOF pores, where photoinduced ring open of photochromic spiropyran blocked hydrogen-bonding network and consequently reduced proton-conduction mobility. These studies explored two applicable methods to modify proton conductivities successfully: (1) light-driven dissociation of protons and (2) photoisomerization of photochromic molecules. The former had few stereo space requirements in the solid matrixes but usually resulted in low switching contrasts (<two times). The latter might yield high switching contrasts but are significantly limited in solid matrixes due to extensive structural changes. Thus, it is highly desirable to explore a new method that can combine the advantages of the two known methods. Additionally, high-contrast enhancement efforts of proton conductivity after light irradiation, instead of weakening the process, are appealing for a real application; however, effective strategies to this aim are also lacking. Electrons and protons often work together in natural photosynthetic and enzymatic systems.18,19 Besides, electron transfer usually results in minor structural change.20,21 Inspired by these points, we presume that electron transfer or electron redistribution in a material system could affect the performance of proton conduction significantly and is well adapted to a solid matrix. Suppose one crystalline compound with an infinite hydrogen-bonding network is able to undergo photoinduced electron transfer (PIET), it can act as a good proof-of-concept model to verify our idea and further explore the regulated mechanism involving the interrelationship of electron transfer and proton transport. Diprotonated 4,4′-bipyridinium (a typical viologen; abbreviated as H2V hereafter) can accept one electron from an electron donor to yield a stable radical and generate a photochromic phenomenon after irradiation.22 The existence of N–H bonds in H2V offers an opportunity to construct a hydrogen-bonding network. If free or coordinated water molecules and/or hydroxyl groups are further included, then the formation of an H-bonded supramolecule with an infinite hydrogen-bonding network is highly possible. Furthermore, crystalline species particularly favor the study of internal structural information. Therefore, crystalline compounds with “H2V,” “free or coordinated water” and/or “hydroxyl” groups are suitable proof-of-concept models to understand the relationship between the PIET process and proton conduction. Experimental Methods Materials and instruments All chemicals of analytical grade were obtained from commercially available sources and used as received without further purification. Powder X-ray diffraction (PXRD) patterns at room temperature were acquired on a Rigaku Miniflex II Desktop X-ray diffractometer (Tokyo, Japan) using Cu Kα radiation (λ = 1.540598 Å) at 40 kV and 40 mA ranging from 5° to 50°. A simulated PXRD pattern was obtained from the Mercury Version 2020.1 software ( http://www.ccdc.cam.ac.uk/products/mercury). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis experiments were carried out on a Mettler TOLEDO simultaneous TGA/DSC apparatus (Zurich, Switzerland) in N2, heating the sample in an Al2O3 crucible at a heating rate of 10 K·min−1. Fourier transform infrared (FT-IR) spectra were recorded on a PerkinElmer Spectrum One FT-IR spectrometer (Waltham, MA) using KCl pellets in the 4000–400 cm−1 range. Electron absorption spectra were measured at room temperature on a PerkinElmer Lambda 900 UV/vis/near-infrared (NIR) spectrophotometer (Waltham, MA) equipped with an integrating sphere and BaSO4 as a reference. Electron paramagnetic resonance (ESR) spectra were recorded on a Bruker-BioSpin ER-420 spectrometer (Rheinstetten, Germany) with a 100 kHz magnetic field in the X band at room temperature. Synthesis of {(H2V)[Ge(ox)2(OH)2]}·2H2O ( 1; ox = oxalate) Compound 1 was synthesized, as described previously.23 The crystal samples for all testing and characterizations were carefully picked with the aid of a microscope, checking their phase purity by PXRD ( Supporting Information Figure S1). Proton conductivity measurements Proton conductivity measurements were performed using a quasi-four-electrode alternating current (AC) impedance technique with a Solartron 1260 impedance/gain-phase analyzer. Our single-crystal measurements revealed the single-crystal shape as a triangular prism, wherein the cross-section area sizes and the length were 0.157 × 0.270 mm2 and 0.350 mm, respectively. Gold wires were connected to both ends of the longer axis of each crystal. The single crystal was measured at frequencies ranging from 107 to 1 Hz as the temperatures were varied from 303 to 323 K and the relative humidity (RH) was 95%. The resistances of the crystalline samples were deduced with the operation of a “fit cycle” from the Debye semicircle in the Nyquist plot. Computational approaches Projected band structure The calculation was based on density functional theory (DFT) in conjunction with the projector augmented wave (PAW) potential, which is implemented in the Vienna ab initio Simulation Package (VASP).24,25 The Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional with an optB86b-vdW correction was used, considering the dispersion interaction between neighboring organic components.26 Single-crystal X-ray diffraction data of 1 were used to build the calculation model. Single-point energy was calculated using plane-wave cutoff energy of 400 eV and a 3 × 3 × 2 Monkhorst–Pack grid of k-points. The dipole moment of a fragment and charge decomposition analysis The calculations indicated above were derived using the Gaussian 09 D01 version and Multiwfn software.27–29 As shown in Supporting Information Figure S8, the molecular model was taken from the single-crystal structure of 1. H atoms in the Ge complex and the water molecule were optimized at the M06-2X/def2-svp level, while other atoms remained unchanged. The dipole moment of a fragment (F) based on the Hirshfeld weighting function given by the equation: D F = ∑ A ∈ F [ Z A R A − ∫ [ ω A ( r ) ρ ( r ) ] r d r ] where A is the atomic index in F, ZA, RA, and ωA(r) are nuclear charge, position, and atomic weighting function of atom A, respectively.28 The charges were set as −2 and −1 for the Ge complex in initial and colored states. The charge decomposition analysis (CDA) proposed by Dapprich and Frenking is used to provide a deep insight into how charges are transferred within fragments in a complex to achieve charge equilibrium.27 In CDA, the fragment orbital (FO) denotes the molecular orbital (MO) of a fragment in its isolated state. Three terms are defined as follows: d i = ∑ m ∈ A occ ∑ n ∈ B vir η i C m , i C n , i S m , n b i = ∑ m ∈ A vir ∑ n ∈ B occ η i C m , i C n , i S m , n r i = ∑ m ∈ A occ ∑ n ∈ B occ η i C m , i C n , i S m , n where i and η are index and occupation number of MO of complex, respectively. S m , n = ∫ f m ( r ) f n ( r ) d r is an overlap integral between FO m and FO n. Cm,i denotes the coefficient of FO m in MO i of the complex. The superscript “vir” and “occ” mean virtual (viz. unoccupied) and occupied, respectively. The term di denotes the amount of electron donated from fragment A to B via MO i of the complex; similarly, the term bi denotes the electron back donated from B to A. The term r reveals closed-shell interaction between two occupied FOs in different fragments; a positive value of ri means that owing to MO i, the electrons of the two fragments are accumulated in their overlap region and shows bonding character, while a negative value indicates that the electrons are depleted from the overlap region, and thus, reflect an electron repulsive effect. In the initial state, the charges for the Ge complex, water, and H2V were set as −2, 0, and +2, respectively, while those in the colored state were set as −1, 0, and +1, respectively. The spin multiplicities were set as 1 and 3 for initial and colored states of the model complex, respectively. Results and Discussion Through screening of the Cambridge Crystallographic Data Center (CCDC) database, 185 structures with “H2V,” “free or water,” and/or “hydroxyl” were found ( Supporting Information Figures S2 and S3). From these structures, compound 123 was chosen as a proof-of-concept model, considering its well-resolved crystal structure, the presence of an infinite hydrogen-bonding network, and potential electron-transfer photochromic property. Figure 1 shows that compound 1 was constructed by H2V ions, Ge complexes, and free water molecules through intermolecular hydrogen bonds and van der Waals interactions. In the Ge complex, each Ge atom was coordinated by six oxygen atoms from two ox ligands and two hydroxyl groups to form a distorted octahedron. The coordinated O(9) hydroxyl groups and free O(2W) water molecules form an infinite hydrogen-bonding network along a direction that provides 1D proton-transporting channels. Notably, the hydrogen atoms of the O(9) hydroxyl group and the O(2W) water molecule were found to be disordered over two distinct crystallographic positions [H(4W) and H(5W) for the water molecule, and H(9A) and H(9B) for the hydroxyl group].23 This disorder means that the active O(9) hydroxyl group and the O(2W) water molecule can reorient themselves readily to make the oxygen atoms have a proper angle to accept hydrogen atoms for proton transport through the Grotthuss mechanism.30,31 Moreover, it has been reported that the electron on the oxygen atoms of an ox could transfer to H2V after irradiation in a photochromic process.32 The nearest distance between the ox oxygen atom and the H2V nitrogen atom in 1 was about 2.811(3) Å, which met the distance of typical PIET occurrence.33,34 Therefore, compound 1 has a high probability of exhibiting electron-transfer photochromic properties. Figure 1 | Crystal structure of 1 showing an infinite hydrogen-bonding network along the a axis. Hydrogen bonds: O(2W)–H(4W)⋯O(2W, symmetry codes: −x, 1−y, −z), dO(2W)⋯O(2W) = 2.738(3) Å, ∠[O(2W)–H(4W)⋯O(2W)] = 161(4)°; O(9)–H(9B)⋯O(2W), dO(9)⋯O(2W) = 3.188(3) Å, ∠[O(9)–H(9B)⋯O(2W)] = 119(3)°; O(9)–H(9B)⋯O(9, symmetry codes: 1−x, 1−y, −z), dO(9)⋯O(9) = 3.004(4) Å, ∠[O(9)–H(9B)⋯O(9)] = 133(5)°; O(9)–H(9A)⋯O(2W, symmetry codes: 1−x, 1−y, −z), dO(9)⋯O(2W) = 2.800(3) Å, ∠[O(9)–H(9A)⋯O(2W)] = 161(6)°. Partial disordered H atoms are drawn in light green. The green arrows indicate the proton transport channel by the Grotthuss mechanism. Download figure Download PowerPoint Our experimental data could well demonstrate the above speculation. Upon continuous irradiation by a diode-pumped solid-state (DPSS) laser (355 nm, 369 mW·cm−1) for only 30 s under ambient conditions, the colorless as-synthesized crystalline sample ( 1A) underwent a rapid, apparent color change to a purple sample ( 1B) (Figure 2a). No generation of prominent new peaks or disappearance of old peaks was observed in the PXRD pattern ( Supporting Information Figure S1), indicating no evident structural change during the coloration process. Furthermore, TGA curves before and after the coloration also displayed no noticeable difference, which suggested that the free water molecules were not lost after coloration ( Supporting Information Figure S5). These results excluded the occurrence of photoinduced dissociation after the coloration. Additionally, two characteristic electron absorption bands of viologen radicals35 appeared around 386 and 596 nm after the coloration (Figure 2c). Time-dependent absorption data indicated that the coloration process occurred rapidly and reached saturation after 2 min of irradiation. The coloration–decoloration process for 1 could be cycled at least four times ( Supporting Information Figure S6), revealing its reversible photochromism character.36 An EPR study revealed no signal for 1A, but a strong, sharp single-line signal at g = 2.0025 for 1B (Figure 2b). Both electron absorption and EPR data demonstrate the occurrence of a PIET process and the formation of H2V radicals after coloration. We confirmed the electron donor by calculating the projected band structure of 1. As illustrated in Figure 2d, the electronic states near the valence band maximum (VBM) were mainly dominated by an ox, while the conduction band minimum (CBM) was exclusively contributed by H2V. These features indicated that ox and H2V were the electron donor and acceptor, respectively. This deduction was consistent with the previous discovery in the literature that ox is an effective electron donor.32 The 1B sample could be bleached by allowing to stand in the dark in air, but complete bleaching required 2 days, as monitored by the EPR study (Figures 2a and 2b). Figure 2 | Photochromism of 1: reversible color change (a) and EPR spectra (b) in a cycle (1A, as-synthesized sample; 1B, colored sample; decolored, color-bleached sample). (c) Time-dependent electron absorption spectra upon irradiation. (d) Projected band structure with the Fermi level was set to zero by default. Download figure Download PowerPoint Proton conductivities (σ) of a single crystal of 1 were investigated by impedance spectroscopy using silver paste as electrodes with resistance extracted by fitting the corresponding Nyquist plot. As shown in Figure 3a, the Nyquist plot impedance data on the 95% RH at 303 K showed that the 1A sample has a σ value of 2.83 × 10−5 S·cm−1. After irradiation for 2 min by the DPSS laser to produce the 1B the σ value increased by about 54 times to × S·cm−1. This is the hitherto largest for light-responsive proton Thus, the above results confirmed that a light-responsive proton could be by the PIET Figure 3 | (a) Nyquist plot of the impedance of 1A and 1B under 303 K and 95% an of (b) proton conductivities of 1A and 1B at 95% of the single-crystal samples Download figure Download PowerPoint gain insight into the electron transfer an increase in proton proton conductivities were TGA revealed that compound 1 could be stable to this the free water molecules to ( Supporting Information Figure 95% the σ of 1A and 1B increased from 2.83 × 10−5 to × and from × to × respectively, with the temperature from 303 to 323 K (Figure The = based on the along with the has often been applied to the proton conduction in The calculated energy of 1A and 1B are around and (Figure and Supporting Information Figure The decrease of after irradiation indicated a in the proton conduction to an increase in the σ further understand the for increased proton conduction after irradiation FT-IR spectra were recorded (Figure As the irradiation the relative of around cm−1 for and groups while the of peaks remained unchanged. Moreover, and positions of other peaks not of a mode on the change in dipole moment by the where and were the dipole moment and the respectively. The the in of atoms connected at both ends of one chemical the the change in during and the the one electron transferred from the Ge complex to the electron density of the Ge complex The decrease in electron density the in between and H atoms in the hydroxyl group of the Ge complex, which tended to the value of the hydroxyl with a decrease in the The calculated of the O(9) hydroxyl fragment ( Supporting Information showed that the of the dipole moment reduced from to Debye after electron consistent with the above Therefore, the decrease in the of the hydroxyl group reduced the of the hydrogen bonds between the hydroxyl group and the free water molecule, in increased the proton on the hydroxyl and water groups and the proton conduction Figure | (a) of the of 1 in the upon irradiation. (b) of complex and with green and set at respectively. Download figure Download PowerPoint provides a insight into the electron influence on proton conduction from an electronic structural As shown in Figure the of orbital the overlap region between the hydroxyl group and the water molecule with a large positive r value which indicated a bonding In a in the overlap region in orbital with a large negative r value an electron repulsive (Figure Supporting Information S2 and and Figure The typical bonding and the hydrogen-bonding relationship within the hydroxyl group and water the hydrogen-bonding relationship mainly contributed to charge transfer between the Ge complex and water As shown in the electrons were transferred from the Ge complex to the water molecule due to the corresponding complex orbital This is in with our chemical in that the hydroxyl atom provided electrons to form a hydrogen with the proton in the water molecule, to the formation The decrease in from to between the Ge complex and the water molecule after coloration resulted in hydrogen-bonding the H atoms in the water molecule high and increased proton 1 | Results for a of One Ge and One in 1 d b r state state The term d denotes the number of electrons donated from the Ge complex to the water The term b denotes the electrons donated back from the water molecule to the Ge complex. The term that the Ge complex provides its electrons from occupied FOs to virtual FOs of the water The term r reveals closed-shell interaction between two occupied FOs in different We have shown in a first to modify proton conduction by the PIET Through functional structural we were able to one proof-of-concept crystalline photochromic viologen-based H-bonded supramolecule from the For a real high-contrast enhancement of proton conductivity after light irradiation is highly the of our only one known has shown proton conductivity upon irradiation and the observed of ca. one time, which is In this the proton conductivity for the proof-of-concept compound increased to ca. 54 times after a for light-responsive proton The increased proton conductivity was derived from a decrease in the energy of the proton transport by the weakening of the hydrogen-bonding interaction after A of the relationship between the electron-transfer process and proton conduction and the of high for the PIET method inspire the exploration of photon conductors with higher proton conductivities or switchable smart systems with high contrasts. 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Nathan Martindale, Scott Stewart, Mark Adams, Greg Westphal

In international nuclear safeguards, the International Atomic Energy Agency (IAEA) is tasked with inspecting and verifying nuclear facilities and their activities. Data analytics and machine learning to support inspections require large amounts of data that nuclear facility operators may consider proprietary or sensitive, so the IAEA may not have full access. Allowing computation over private data without compromising its security therefore has value for safeguards inspections and analysis. Privacy-preserving machine learning (PPML) consists of security-focused techniques that allow data analytics and machine learning algorithms to run on sensitive data without revealing it. This includes ideas like homomorphic encryption (HE), secure multiparty computation (SMPC), and secure enclaves. HE allows algorithms and mathematical operations to be conducted directly on the encrypted data instead of first decrypting it. With SMPC, multiple entities collaboratively compute over distributed data such that no party is able to directly view any others’ original data. Secure enclaves allow computation to take place in a separate and heavily blocked-off section of a CPU. Techniques like these allow for several potential use cases in which the security of data is essential. With SMPC, machine learning models can be trained over the input data from multiple entities, resulting in a model that all users can benefit from without leaking the input data from any particular entity. With SMPC or a zero-knowledge proof (ZKP), an algorithm returning some single answer or truth value can be run on someone else’s data without ever needing to see that data, potentially allowing for verification or proof of some underlying question. HE can allow for outsourcing computation on data to a hostile or untrusted environment. Although most of the research in this field resides within the health and financial domains, tools from PPML may have similar applications in nuclear safeguards. Allowing the IAEA to compute over proprietary information, such as process models and raw sensor data using PPML techniques, provides the baseline for running complex analytics without needing direct unencrypted access to the underlying data, maintaining its privacy. Important limitations to consider for these techniques include the efficiency and level of security required. The security of HE and SMPC come at the cost of speed—the significant amount of overhead means that algorithms implemented in these protocols and encryption schemes are slower than when run on plaintext. Additionally, several important parameters determine what techniques or protocols are used based on the security requirements. SMPC protocols may need to be selected for resistance against a party that attempts to deviate from the protocol to distort the result or gain access to additional information, and a protocol secure against these attacks may further increase the overhead of the algorithm.

Sergey Zapechnikov

The paper is devoted to the actual problem of ensuring privacy during performing transactions in distributed ledgers. We discuss various aspects of transaction privacy, as well as the specifics of setting the problem for distributed ledgers with two main models for representing participants' balances: the UTXO-model and the account model. Based on these results, we outline definitions and consider security properties of the main cryptographic primitives used for preserving the privacy of transactions: mixers, ring signatures, homomorphic encryption, and zero-knowledge proofs. We analyze well-known solutions for distributed ledgers based on the UTXO-model, such as Zcash, Monero, Zcoin, Dash, CoinShuffle, Verge, Grin, and others, as well as for systems based on the account model: DSC, Zether, Zeth, BlockMaze. Based on the comparison of advantages, disadvantages, and limitations for existing solutions, conclusions are drawn about the future development of distributed ledgers that ensure the privacy of transactions, and new research tasks are outlined.

Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

An efficient member revocation mechanism is a desirable feature when group signature schemes are applied in practical scenarios. Revocation methods, such as verifier-local revocation (VLR), provide an efficient member revocation in applications of group signatures. However, VLR-group signatures rely on a weaker security notion. On the other hand, group signature schemes for static groups gain stronger security with the full-anonymity security notion. Even though an outsider sees the secret signing keys of all group members in the full-anonymity, the signer is still anonymous. Achieving the full-anonymity for VLR group signature schemes is challenging due to the structure of secret signing keys. The secret signing keys of those schemes consist of tokens, which are used to manage revocation. The reveal of tokens may destroy the anonymity of the signers. We obtain stronger security for the lattice-based VLR group signature schemes by providing a new key generation method, which outputs revocation tokens without deriving from the members’ secret signing keys. We propose a new group signature scheme from lattices with VLR, which achieves stronger security than the previous related works. To avoid signature forgeries, we suggest a new zero-knowledge proof system that requires signers to validate themselves. Moreover, we output an efficient tracing mechanism.

A. V. Siriak, Valentina Turchyna

The problem of constructing a NIZK proof of knowledge of a multivariate polynomial’s zero is considered. A previously developed method for SNARK construction based on Quadratic Arithmetic Programs and Pinocchio protocol is adapted to solve the stated problem efficiently.

Ryan Henry, Alyssa Tory, Sophie Henry, Isabella Henry · 5 authors

In this short paper, we revisit the celebrated Naor?Naor?Reingold (NNR) protocol for ?[convincing] people you know where Waldo is without revealing information about his location?. We observe that, despite oft-repeated claims to the contrary, the NNR protocol is neither zero-knowledge nor a proof of knowledge. We propose a slightly more elaborate version that is both of these things?but still eminently suitable for children?s playdates (and the classroom).

Suthee Ruangwises, Toshiya Itoh

An undirected graph $G$ is known to both the prover $P$ and the verifier $V$, but only $P$ knows a subgraph $H$ of $G$. Without revealing any information about $H$, $P$ wants to convince $V$ that $H$ is a connected spanning subgraph of $G$, i.e. $H$ is connected and contains all vertices of $G$. In this paper, we propose an unconventional zero-knowledge proof protocol using a physical deck of cards, which enables $P$ to physically show that $H$ satisfies the condition without revealing it. We also show applications of this protocol to verify solutions of three well-known NP-complete problems: the Hamiltonian cycle problem, the maximum leaf spanning tree problem, and a popular logic puzzle called Bridges.

Suthee Ruangwises, Toshiya Itoh

No abstract is available for this record.

Ky Nguyen, Miguel Ambrona, Masayuki Abe

The problem of fair exchange consists of interchanging goods between two parties that do not trust each other. Despite known impossibility results, recent works leverage the block-chain and zero-knowledge proofs to implement zero-knowledge contingent payment (zkCP) systems that make fair exchange of digital goods possible. Implementing these systems in a secure and efficient way is a big challenge, as evidenced by several unsuccessful attempts from the literature. Campanelli et al. (ACM CCS 2017) discovered a vulnerability on an existing zkCP proposal based on SNARKs (succinct non-interactive arguments of knowledge) and suggested several repairs. Fuchsbauer (ACM CCS 2019) found a flaw in the mentioned countermeasures. In particular, he showed that witness-indistinguishability (WI) is not sufficient for the zkCP schemes proposed by Campanelli et al. to be secure. In this work, we observe that a slightly stronger notion of WI, that we coin trapdoor subversion WI (tS-WI), rules out Fuchsbauer's attack. We formally define security properties for CP systems and show that, under tS-WI, Campanelli et al.'s proposal indeed satisfies these properties. Additionally, we explore alternative approaches to implement ZK (other than SNARKs) and develop a prototype, using it to demonstrate their potential. Our new ideas result in a protocol to sell ECDSA signatures with contingent payment that can be executed in less than $150$ milliseconds over a LAN network.

Rishabh Bhadauria, Zhiyong Fang, Carmit Hazay, Muthuramakrishnan Venkitasubramaniam · 6 authors

This paper follows the line of works that design concretely efficient transparent sublinear zero-knowledge Interactive Oracle Proofs (IOP). Arguments obtained via this paradigm have the advantages of not relying on public-key cryptography, not requiring a trusted setup, and resistance to known quantum attacks. In the realm of transparent systems, Ligero and Aurora stand out with incomparable advantages where the former has a fast prover algorithm somewhat succinct proofs and the latter has somewhat fast prover and succinct proofs. In this work, we introduce Ligero++ that combines the best features of both approaches to achieve the best of both worlds. We implement our protocol and benchmark the results.

David Heath, Vladimir Kolesnikov

Zero-Knowledge (ZK) proofs (ZKP) are foundational in cryptography. Most recent ZK research focuses on non-interactive proofs (NIZK) of small statements, useful in blockchain scenarios. Another line, and our focus, instead targets proofs of large statements that are useful, e.g., in proving properties of programs in ZK. We specify a zero-knowledge processor that executes arbitrary programs written in a simple instruction set, and proves in ZK the correctness of the execution. Such an approach is well-suited for constructing ZK proofs of large statements as it efficiently supports complex programming constructs, such as loops and RAM access. Critically, we propose several novel ZK improvements that make our approach concretely efficient: (1) an efficient arithmetic representation with conversions to/from Boolean, (2) an efficient read-only memory that uses $2łog n$ OTs per access, and (3) an efficient read-write memory, øurram, which uses $\frac1 2 łog^2 n$ OTs per access. øurram beats linear scan for RAM of size $>3$ elements! Prior ZK systems used generic ORAM costing orders of magnitude more. We cast our system as a garbling scheme that can be plugged into the ZK protocol of [Jawurek et al, CCS'13]. Put together, our system is concretely efficient: for a processor instantiated with $512$KB of main memory, each processor cycle costs $24$KB of communication. We implemented our approach in \textttC++. On a 1Gbps LAN our implementation realizes a $2.1$KHz processor.

Jiaheng Zhang, Zhiyong Fang, Yupeng Zhang, Dawn Song

Machine learning has become increasingly prominent and is widely used in various applications in practice. Despite its great success, the integrity of machine learning predictions and accuracy is a rising concern. The reproducibility of machine learning models that are claimed to achieve high accuracy remains challenging, and the correctness and consistency of machine learning predictions in real products lack any security guarantees. In this paper, we initiate the study of zero knowledge machine learning and propose protocols for zero knowledge decision tree predictions and accuracy tests. The protocols allow the owner of a decision tree model to convince others that the model computes a prediction on a data sample, or achieves a certain accuracy on a public dataset, without leaking any information about the model itself. We develop approaches to efficiently turn decision tree predictions and accuracy into statements of zero knowledge proofs. We implement our protocols and demonstrate their efficiency in practice. For a decision tree model with 23 levels and 1,029 nodes, it only takes 250 seconds to generate a zero knowledge proof proving that the model achieves high accuracy on a dataset of 5,000 samples and 54 attributes, and the proof size is around 287 kilobytes.

Xavier Salleras, Vanesa Daza

5G communications proposed significant improvements over 4G in terms of efficiency and security. Among these novelties, the 5G Network Slicing seems to have a prominent role: deploy multiple virtual network slices, each providing a different service with different needs and features. Like this, a Slice Operator (SO) ruling a specific slice may want to offer a service for users meeting some requirements. It is of paramount importance to provide a robust authentication protocol, able to ensure that users meet the requirements, but providing at the same time a privacy-by-design architecture. This makes even more sense having a growing density of Internet of Things (IoT) devices exchanging private information over the network. In this paper, we improve the 5G network slicing authentication using a Self-Sovereign Identity (SSI) scheme: granting users full control over their data. We introduce an approach to allow a user to prove his right to access a specific service without leaking any information about him. Such an approach is SANS, a protocol that provides non-linkable protection for any issued information, preventing an SO or an eavesdropper from tracking users' activity and relating it with their real identities. Furthermore, our protocol is scalable and can be taken as a framework for improving related technologies in similar scenarios, like authentication in the 5G Radio Access Network (RAN) or other wireless networks and services. Such features can be achieved using cryptographic primitives called Zero-Knowledge Proofs (ZKP). Upon implementing our solution using a state-of-the-art ZKP library and performing several experiments, we provide benchmarks demonstrating that our approach is affordable in speed and memory consumption.

Benfano Soewito, Yonathan Marcellinus

It has been predicted that more devices will be connected to the internet network along with the development of IoT, and that will increase the complexity in the security system. The most important thing in security systems is the process of encryption and authentication. Various encryption techniques are developed to overcome security problems of the data. One of the methods used for authentication of data is Zero Knowledge Proof. This method works to identify the authenticity of someones statement to proof without showing any knowledge of the statement mentioned. This research will mainly discuss about the security of data transmission system by combining data encryption and data authentication. The proposed data encryption is using Advanced Encryption System and method for authentication of data using the Zero Knowledge Proof. This research will conduct the development methods of authentication Zero Knowledge Proof from previous research and the result was compared with the proposed method based on the simulation results transmission system client and server. Experiments will be conducted using thirty-text data, each of data will be measured on the performance of both encryption and authentication process between the previous method and proposed method. Experimental results show the performance of the proposed method has better speed to process application for security of data transmission systems, with performance to authenticate approximately 5 ms from the client side and server side.

Anders Dalskov, Daniele Lain, Enis Ulqinaku, Kari Kostiainen · 5 authors

Encrypted cloud storage services are steadily increasing in popularity, with many commercial solutions currently available. In such solutions, the cloud storage is trusted for data availability, but not for confidentiality. Additionally, the user's device is considered secure, and the user is expected to behave correctly. We argue that such assumptions are not met in reality: e.g., users routinely forget passwords and fail to make backups, and users' devices get stolen or become infected with malware. Therefore, we consider a more extensive threat model, where users' devices are susceptible to attacks and common human errors are possible. Given this model, we analyze 10 popular commercial services and show that none of them provides good confidentiality and data availability. Motivated by the lack of adequate solutions in the market, we design a novel scheme called Two-Factor Encryption (2FE) that draws inspiration from two-factor authentication and turns file encryption and decryption into an interactive process where two user devices, like a laptop and a smartphone, must interact. 2FE provides strong confidentiality and availability guarantees, as it withstands compromised cloud storage, one stolen or compromised user device at a time, and various human errors. 2FE achieves this by leveraging secret sharing with additional techniques such as oblivious pseudorandom functions and zero-knowledge proofs. We evaluate 2FE experimentally and show that its performance overhead is small. Finally, we explain how our approach can be adapted to other related use cases such as cryptocurrency wallets.