IoT group communication allows users to control multiple IoT devices simultaneously. A convenient method for implementing this communication paradigm is by leveraging software-defined networking (SDN) and allowing IoT endpoints to “advertise” the resources that can be accessed through group communication. In this paper, we propose a solution for securing this process by preventing IoT endpoints from advertising “fake” resources. We consider group communication using the constrained application protocol (CoAP), and we leverage Web of Things (WoT) Thing Description (TD) to enable resources’ advertisement. In order to achieve our goal, we are using linked-data proofs. Additionally, we evaluate the application of zero-knowledge proofs (ZKPs) for hiding certain properties of a WoT-TD file.
The amount of information generated grows as more and more sensor and IoT devices are deployed in smart cities. It is of utmost importance for us to consider the privacy data leakage and compromised identity from both outside adversaries and inside abuse of data access privilege. The security assumption of the system should not solely rely on the fact that permission and access control were being implemented correctly. Quite the contrary, a system can be designed in a way that user's identity data and usage traces are not leaked even if the system had been compromised. Based upon our previous on-street parking system utilizing Bluetooth Low Energy (BLE) beacons, we applied a cryptographic primitive called zero-knowledge proof to our authentication system. A commitment scheme and Merkle tree is combined in the setup to achieve zero-knowledge set membership proof. Doing so, the user is anonymous to the server between authentication sessions, while the server's still able to verify the legitimacy of such user. The on-street parking system is therefore immune to privacy data leakage, as for now one cannot mass-query and profile certain user's traces within the system.
We propose a technique to construct physical Zero-Knowledge Proof (ZKP) protocols for puzzles that require a single loop draw feature. Our approach is based on the observation that a loop has only one hole and this property remains stable by some simple transformations. Using this trick, we can transform a simple big loop, which is visible to anyone, into the solution loop by using transformations that do not disclose any information about the solution. We illustrate our technique by applying it to construct physical ZKP protocols for two Nikoli puzzles: Slitherlink and Masyu.
We consider the problem of efficiently inferring interventional distributions in a causal Bayesian network from a finite number of observations. Let $\mathcal{P}$ be a causal model on a set $\mathbf{V}$ of observable variables on a given causal graph $G$. For sets $\mathbf{X},\mathbf{Y}\subseteq \mathbf{V}$, and setting ${\bf x}$ to $\mathbf{X}$, let $P_{\bf x}(\mathbf{Y})$ denote the interventional distribution on $\mathbf{Y}$ with respect to an intervention ${\bf x}$ to variables ${\bf x}$. Shpitser and Pearl (AAAI 2006), building on the work of Tian and Pearl (AAAI 2001), gave an exact characterization of the class of causal graphs for which the interventional distribution $P_{\bf x}({\mathbf{Y}})$ can be uniquely determined. We give the first efficient version of the Shpitser-Pearl algorithm. In particular, under natural assumptions, we give a polynomial-time algorithm that on input a causal graph $G$ on observable variables $\mathbf{V}$, a setting ${\bf x}$ of a set $\mathbf{X} \subseteq \mathbf{V}$ of bounded size, outputs succinct descriptions of both an evaluator and a generator for a distribution $\hat{P}$ that is $\varepsilon$-close (in total variation distance) to $P_{\bf x}({\mathbf{Y}})$ where $Y=\mathbf{V}\setminus \mathbf{X}$, if $P_{\bf x}(\mathbf{Y})$ is identifiable. We also show that when $\mathbf{Y}$ is an arbitrary set, there is no efficient algorithm that outputs an evaluator of a distribution that is $\varepsilon$-close to $P_{\bf x}({\mathbf{Y}})$ unless all problems that have statistical zero-knowledge proofs, including the Graph Isomorphism problem, have efficient randomized algorithms.
Abstract This paper presents HashWires, a hash-based range proof protocol that is applicable in settings for which there is a trusted third party (typically a credential issuer) that can generate commitments. We refer to these as “credential-based” range proofs (CBRPs). HashWires improves upon hashchain solutions that are typically restricted to micro-payments for small interval ranges, achieving an exponential speedup in proof generation and verification time. Under reasonable assumptions and performance considerations, a Hash-Wires proof can be as small as 305 bytes for 64-bit integers. Although CBRPs are not zero-knowledge and are inherently less flexible than general zero-knowledge range proofs, we provide a number of applications in which a credential issuer can leverage HashWires to provide range proofs for private values, without having to rely on heavyweight cryptographic tools and assumptions.
Fuchang Xu, Dehui Weng, Xiang Li, Yang Li · 5 authors
Open AccessCCS ChemistryRESEARCH ARTICLE14 Jul 2022Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation Fuchang Xu, Dehui Weng, Xiang Li, Yang Li and Junqi Sun Fuchang Xu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Dehui Weng State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Xiang Li State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Yang Li *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 and Junqi Sun State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 https://doi.org/10.31635/ccschem.021.202101111 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail It is highly desirable to develop a solar-driven interfacial water evaporator with a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination; however, this process is considerably challenging. Herein, by exploiting the advantages of a self-healing hydrophilic polymer, a self-healing hydrophilic porous photothermal (SHPP) membrane was fabricated by curing a mixture of the polymer, carbon black, and NaCl, followed by removal of the NaCl from water. Since the SHPP membrane could serve as a photothermal layer and water transportation channel simultaneously, a solar-driven interfacial evaporator could be fabricated readily by assembling the SHPP membrane with polyethylene foam. We have shown that the SHPP membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m−2 h−1 and an energy efficiency of 97.3%. These values are superior to those obtained using solar-driven interfacial evaporators with self-healing capability. Notably, by hydrogen bonds reformation between the fracture surfaces, the SHPP membrane could regain its structural integrity after breaking, making the SHPP membrane-based evaporator the first to heal entirely and repeatedly from physical damage to sustain its water evaporation capacity. Therefore, the potential of using SHPP membranes to develop stable, long-lasting, and high-efficiency solar-driven interfacial water evaporators is highlighted. Download figure Download PowerPoint Introduction Fresh water, accounting for only 3% of the total water resources on earth, is vital to human survival and social development. However, with increased population, as well as persistent environmental pollution, the shortage of fresh water has become a key global issue. Therefore, it is imperative to develop effective technologies to generate fresh water from seawater or sewage.1–3 Among all the water treatment technologies, solar-driven evaporation has attracted extensive research attention due to the environment-friendly and renewable characteristics of solar energy.4 Recently, solar-driven interfacial water evaporation, which minimizes thermal dissipation and applies most of the heat to the liquid–vapor phase transition by concentrating heat at the water–air interface, has been developed to improve the water evaporation efficiency.5–17 Generally, most of the reported solar-driven interfacial evaporators comprise three parts18,19 (Scheme 1a1: (1) a photothermal layer with broadband light absorption and high photothermal conversion, (2) a floatable supporting layer with low thermal conductivity, and (3) a hydrophilic water channel either on the outside or in the middle of the supporting layer that ensures a continuous water supply to the photothermal layer. Although many high-efficiency solar-driven interfacial evaporators have been developed, in practical applications, the photothermal layer or water channel can be damaged by scratching or corrosion, thereby deteriorating the water evaporation efficiency (Scheme 1a2). Hence, to satisfy the requirements for practical applications, it is critical to develop solar-driven interfacial evaporators with a stable water evaporation efficiency. In particular, it is crucial to develop solar-driven interfacial evaporators that can maintain their water evaporation performance after damage. Scheme 1 | (a) Schemes of (1) the composition of a typical solar-driven interfacial evaporator and (2) the loss of its water evaporation capacity due to damage to the water transportation channel. (b) Schematics of (1) the composition of the SHPP membrane-based solar-driven interfacial evaporator and (2) its ability to restore the water evaporation ability via self-healing after physical damage. Download figure Download PowerPoint With the progress in supramolecular chemistry and synthetic chemistry, various self-healing polymers capable of healing damage by themselves to restore the mechanical and/or chemical properties have been synthesized successfully.20–23 In addition, by combining self-healing polymers with functional materials, plenty of self-healing functional materials with superhydrophobicity,24–27 antifouling,28–30 electrical conductivity,31–34 sensing,35–41 and other functions42–50 have been fabricated, decreasing maintenance costs and promoting safety, reliability, and service life significantly. The design and fabrication of self-healing materials with photothermal and water transportation capabilities, able to repair their functions upon damage, would be a judicious solution to increase the stability and service life of solar-driven interfacial evaporators. Although our group and a few other researchers have reported the fabrication of self-healing photothermal membranes for solar-driven water evaporation, these membranes can only heal chemical damage.51,52 Furthermore, the water evaporation rates of these self-healing photothermal membranes were not ideal (<1.31 kg m−2 h−1), related to their hydrophobic/superhydrophobic nature that hindered water transportation and evaporation. Previously, our group reported that self-healing superhydrophobic porous materials with a photothermal conversion ability capable of healing physical damage could be obtained using a self-healing hydrophobic polymer and carbon nanotubes as the main materials using NaCl as the template.53 Based on the experience in self-healing porous materials fabrication, along with the widely available knowledge in hydrophilic self-healing polymer synthesis, a rational selection of the material composition was made that led to self-healing hydrophilic photothermal membranes with long-term advantages of high-efficiency evaporation capability for solar-driven interfacial evaporators. As a proof of concept, for the first time, we are reporting a self-healing hydrophilic porous photothermal (SHPP) membrane for highly efficient solar-driven interfacial water evaporation based on a carefully designed and synthesis of a self-healing hydrophilic polymer. The SHPP membrane was fabricated by curing a mixture of self-healing hydrophilic polymer with carbon black (CB) and NaCl, followed by removing the NaCl from water. By tuning the hydrophilicity of the self-healing polymer and the mass ratios of the feed materials, the water content of the SHPP membrane that considerably affects the water evaporation performance could be controlled. From the self-healing perspective, the self-healing polymer permitted the coalescence of the cut SHPP membrane via the reformation of hydrogen bonds between the fracture surfaces, leading to the healing of structural integrity. As the SHPP membrane could simultaneously serve as the photothermal layer and water transportation channel, a highly efficient solar-driven interfacial evaporator can be readily fabricated by assembling the SHPP membrane with a polyethylene (PE) foam (Scheme 1b1). By floating such a designed evaporator on the water surface, the evaporation rates of lake water and seawater reached 1.67 and 1.61 kg m−2 h−1, respectively. When the water evaporation capacity of the evaporator was lost by cutting the SHPP membrane, it was able to self-heal at room temperature, and the water evaporation performance of the evaporator was fully restored (Scheme 1b2). Moreover, the SHPP membrane was capable of healing damage caused at the exact location repeatedly without losing the water evaporation performance. The simple structure of the SHPP membrane-based evaporator benefits its integration into conventional solar distillation devices. In this study, we fabricated a prototype distillation device comprising an SHPP membrane-based evaporator to demonstrate the applicability of the SHPP membrane for sewage purification and seawater desalination. Experimental Methods Materials PE glycol (PEG; Mw = 1000) and polyvinyl alcohol (PVA; Mw = 85,000–124,000, 87–89% hydrolyzed) were purchased from Sigma-Aldrich (Shanghai, China). Polytetramethylene ether glycol (PTMG; Mw = 1000) was purchased from Aladdin (Shanghai, China). Dicyclohexylmethane 4,4-diisocyanate (DMDI; purity < 90%) was purchased from TCI Development Co., Ltd. (Shanghai, China). Dibutyltin dilaurate (DBTDL; purity < 97.5%) was purchased from J&K Scientific Ltd. (Beijing, China). Tetrahydrofuran (THF) was purchased from Innochem Science & Technology Co., Ltd. (Beijing, China). CB was purchased from Alfa Aesar Chemical Co., Ltd. (Shanghai, China). Anhydrous ethanol and NaCl were purchased from Beijing Chemical Reagents Company (Beijing, China). All of the chemicals were used without further purification. Synthesis of PUx A series of PUx with different molar ratios of PEG and PTMG were synthesized by the step-growth polymerization of PEG, PTMG, and DMDI. Taking PU50 as an example, PEG (5.00 g, 5 mmol) and PTMG (5.00 g, 5 mmol) were added into a 250 mL three-neck round-bottom flask equipped with mechanical agitation, nitrogen inlet, and condensation reflux. The reaction was allowed to proceed under vacuum for 2 h at 100 °C; then the system was cooled to 60 °C and filled with nitrogen gas. Subsequently, THF (100 mL), DMDI (3.15 g, 12 mmol), and DBTDL (0.05 g, 0.08 mmol) were added into the three-neck round-bottom flask. After 48 h of stirring at 60 °C under nitrogen, the reaction solution was purified by dialysis using a dialysis membrane [molecular weight cutoff (MWCO), 8000–14,000 Da] with anhydrous ethanol. Finally, PU50 was obtained after ethanol evaporation. PU0, PU10, PU20, PU30, and PU40 were synthesized separately in accordance with the method described above. Fabrication of PUx/CBm/NaCln membranes CB and NaCl with different mass ratios were mixed for 30 min using a ball mill machine. Next, CB and NaCl blends were added to 15 mL THF solutions of PUx (the concentration of PUx depended on the composition of PUx/CBm/NaCln), followed by mechanical stirring at 500 rpm for 1 h to ensure that CB and NaCl were well dispersed in the PUx solutions. The resulting solution mixtures were poured into Teflon molds and cured at room temperature. After complete removal of THF, the exteriors of the solidified composite blocks were rubbed with sandpaper and immersed in water baths renewed every 6 h over 2 days to remove the NaCl completely with the resultant PUx/CBm/NaCln porous membranes. The water-soaked PUx/CBm/NaCln porous membranes were wiped with filter papers and then dried at room temperature. Characterization The Mw and PDI of PUx were characterized on a Shimadzu gel-permeation chromatography (GPC; Shimadzu, Japan) system. THF was used as the moving phase, and the flow rate was 1.0 mL min−1. Fourier transform infrared (FT-IR) spectra were taken on a Bruker VERTEX 80 V FT-IR spectrometer (Bruker, Germany). The differential scanning calorimetry (DSC) curves of PUx were obtained on a TA instrument Q200 (TA, USA) at the heating/cooling rate of 10 °C min−1 in a N2 atmosphere. Simulated solar light was provided by a PL-XQ500W xenon lamp (Beijing Springs Technology Co., Ltd., Beijing, China), and the light intensity was kept at 1000 W m−2. Temperature values and IR images of the samples were captured using a HIKVISION H10 thermal imager (HIKVISION, Hangzhou, China). The distance between the sample and the thermal imager was fixed at 20 cm. The accuracy in temperature of the thermal imager is ±2 °C. The reflection and transmission spectra of the samples were characterized by a UV-3600 spectrophotometer (Shimadzu, Kyoto, Japan). The optical images and videos were captured using a Canon PowerShot SX40 HS camera (Canon, China). The scanning electron microscopy (SEM) images were obtained using a JEOL JSM 6700F field emission scanning electron microscope (JEOL, Japan). The optical microscopy images were obtained using an Olympus DP72 optical microscope (Olympus, China). The porosity (ρ) of the PUx/CBm/NaCln porous membrane was calculated by the following equation: ρ = ( M wet − M dry ) / ( M wet − M sub ) (1)where Mdry is the dry mass of the membrane, Mwet is the mass of the prewetted membrane measured in air, and Msub is the mass of the membranes soaked in water. The solar thermal conversion efficiency (η) of the PUx/CBm/NaCln porous membrane was calculated by the following equation: η = H e × ( ν Total − ν Dark ) / Q s , (2)where He is the heat of water evaporation (2260 kJ kg−1), Qs is the incidence light power, νTotal is the evaporation rate of the PUx/CBm/NaCln porous membrane at stable state under one sun irradiation, and νDark is the evaporation rate of the PUx/CBm/NaCln porous membrane in dark environment. To test its water transport capacity, a piece of PUx/CBm/NaCln porous membrane (0.1 cm × 1 cm × 5 cm) was partially immersed in a beaker containing 50 mL of deionized (DI) water, and a piece of filter paper was used to absorb water from the upper end of the membrane continuously. The filter paper was replaced after it was saturated with water. The water flux (F) of the PUx/CBm/NaCln membrane was calculated by the following equation: F = M water / ( S * t ) , (3)where Mwater is the mass change of the DI water in the beaker, S is the cross-sectional area of the membrane, and t is the test time. Results and Discussion The self-healing hydrophilic polymer that was key for fabricating the SHPP membrane with a stable, highly efficient solar-driven interface water evaporation capability was synthesized by the step-growth polymerization of PEG, PTMG, and DMDI, as shown in Figure 1a. The resulting polymers were denoted as PUx, where x referred to the molar percentage of PEG in the total monomers. A peak characteristic of –N=C=O at 2268 cm−1 was not observable in the FT-IR spectra of PUx ( Supporting Information Figure S1). Meanwhile, peaks corresponding to the C=O stretching vibration, as well as N–H stretching and bending vibrations, were observed around 1720 and 1533 cm−1, respectively, confirming the successful synthesis of PUx. GPC was employed to estimate the weight-average molecular weight (Mw) and polydispersity index (PDI) of PUx. Supporting Information Table S1 lists the results. Although the molar ratios of PEG and PTMG were different, all of the PUx exhibited similar Mw and PDI. In this study, hydrophobic PTMG and hydrophilic PEG were used rationally by adjusting the molar ratio of the two monomers due to the regulation of hydrophilicity of PUx. With an increase in the PEG content, the water uptake of PUx increased, indicating that the hydrophilicity of PUx increases with an increase in the molar ratio of PEG ( Supporting Information Figure S2). Figure 1 | (a) Synthetic route of PUx. (b) Photographs of the PU20 film after being cut and being healed at room temperature for 6 h. (c) Microscopy images of the cut PU20 membrane before and after healing for 6 h at room temperature. (d) Stress–strain curves of the pristine PU20 film and the cut PU20 film after healing for different times at room temperatures. The stretching speed was 50 mm min−1. Download figure Download PowerPoint Taking PU20 as a representative, the self-healing ability of PUx was examined. A piece of the PU20 film (0.6 cm × 3.5 cm) was cut in half with a knife, and the two parts were subsequently reattached closely (Figure 1b). After placing the PU20 film under ambient conditions for 6 h, the separated PU20 film was conglutinated together, restoring its structural integrity. In addition, an optical microscopy image confirmed that the cut was healed completely (Figure 1c). The self-healing ability of PU20 was attributed to its abundant reversible hydrogen bonds and low glass transition temperature (−51.3 °C, Supporting Information Figure S3). When the fracture surfaces were brought into close contact, the polymer chains migrated gradually into the voids, and the hydrogen bonds reformed with one another, leading to healing of the cut.54 Tensile tests were employed to characterize the healing ability of PU20 further. As the healing time increased, the fracture stress of the healed PU20 film increased gradually and recovered to 4.26 MPa after 6 h of healing at room temperature (Figure 1d). Accordingly, the healing efficiency of PU20, defined as the proportion of the restored fracture stress to the original stress, was calculated to be 98.4%, indicating a satisfactory self-healing ability. In addition, the self-healing abilities of PUx with different PEG contents were examined. Supporting Information Table S2 lists the results. With an increase in the PEG content, the healing efficiency of PUx increased due to the reduction in Young's modulus of the resulting polymer via an increase in the PEG segments ( Supporting Information Table S2). With the successful synthesis of PUx, SHPP membranes were fabricated using PUx, CB, and NaCl. CB was used due to its good photothermal conversion ability and low costs,55,56 while NaCl was used as a sacrificial template. The self-healing hydrophilic porous PUx/CBm/NaCln membranes, where m and n represent the mass ratios of CB and NaCl to PUx, respectively, were fabricated by casting a dispersion of PUx, CB, and NaCl in THF into a Teflon (R) mold, followed by solvent evaporation and NaCl removal in water (Figure 2a). Owing to the simple fabrication, a piece of PU20/CB0.5/NaCl5 membrane with dimensions of 11 cm × 11 cm was obtained readily (Figure 2b). The SEM image in Figure 2c reveals that the PU20/CB0.5/NaCl5 membrane exhibits a three-dimensional interconnected hierarchical porous structure, comprising a CB-reinforced PU20 skeleton and macropores with diameters ranging from 9.7 to 109.8 μm. Based on Archimedes' method (eq 1), the porosity of the PU20/CB0.5/NaCl5 membrane was 59.8%. Figure 2 | (a) Schematic of the fabrication processes of the PUx/CBm/NaCln membranes. (b) Photographs of the PU20/CB0.5/NaCl5 membrane. (c) Cross-section SEM image of the PU20/CB0.5/NaCl5 membrane. (d) Photograph showing that the PU20/CB0.5/NaCl5 membrane transported water to a height of 5 cm in 3 min. (e) Photograph of the PU20/CB0.5/NaCl5 membrane-based solar-driven interfacial evaporator. (f) Temperature changes of DI water and the PU20/CB0.5/NaCl5 membrane-based evaporator floating on the DI water under simulated solar light irradiation. (g) Time-sequence IR images of the DI water-filled glass containers without (left) and with (right) the PU20/CB0.5/NaCl5 membrane-based evaporator under simulated solar light irradiation for (1) 1 min and (2) 60 min. (h) The mass changes of the DI water with and without the PU20/CB0.5/NaCl5 membrane-based evaporator under simulated solar light irradiation. Download figure Download PowerPoint The combination of the hydrophilicity of PU20 and the porous structure permitted a 5 cm vertical transport of water by the PU20/CB0.5/NaCl5 membrane due to capillary force (Figure 2d), qualifying it to be a water transportation channel. In addition, the average transmittances and reflections of the PU20/CB0.5/NaCl5 membrane were close to zero in the wavelength range from 200 to 2500 nm ( Supporting Information Figure S4). The intense light absorption of the PU20/CB0.5/NaCl5 membrane was related to the excellent light absorption performance of the CB in a broad wavelength range and the porous structure. This further improved the solar-energy harvesting efficiency via a reduction in light reflection.57 Next, the photothermal ability of the PU20/CB0.5/NaCl5 membrane was investigated by irradiating the membrane with a simulated solar light (1000 W m−2), then an IR camera was used to monitor the temperature of the membrane in air. Under light irradiation, the temperature of the PU20/CB0.5/NaCl5 membrane increased rapidly to 57 °C in 1 min and then reached a steady-state temperature of 70 °C by 5 min ( Supporting Information Figure S5), demonstrating an excellent photothermal ability. As the PU20/CB0.5/NaCl5 membrane simultaneously exhibited excellent water transport and photothermal abilities, we envisioned that a simple efficient solar-driven interfacial water evaporator could be readily by the PU20/CB0.5/NaCl5 membrane a PE foam to serve as a and an layer simultaneously (Figure The water evaporation performance of the PU20/CB0.5/NaCl5 membrane-based evaporator floating on the water was measured by placing the evaporator in a DI water-filled glass on an Simulated light with an intensity of 1000 W m−2 was on the PU20/CB0.5/NaCl5 membrane surface, and the water mass change was Under light irradiation, the PU20/CB0.5/NaCl5 membrane light and the water The temperature of the PU20/CB0.5/NaCl5 membrane rapidly increased to °C in 1 min and reached a steady-state temperature of °C by 5 min (Figure and Since the PU20/CB0.5/NaCl5 membrane transported water from the glass to the of the evaporator (Scheme this membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m−2 h−1 (Figure to 2 provided in the Experimental the solar thermal conversion efficiency of the PU20/CB0.5/NaCl5 membrane-based evaporator was 97.3%. we that such a high solar thermal conversion efficiency for the evaporator was related to the that most of the heat was used to the water at the of the evaporator and that only a of the heat was to the water the glass As after 1 h of simulated light irradiation, the temperature of the water under the evaporator only increased by 5 °C (Figure In the temperature of water in the glass without the PU20/CB0.5/NaCl5 membrane-based evaporator increased by °C after 1 h of simulated light irradiation (Figure Owing to the low light absorption capacity of water and water the evaporation rate of water in the glass without the evaporator was only kg m−2 h−1 (Figure with the of the PU20/CB0.5/NaCl5 membrane-based the evaporation rate of water increased Subsequently, the of the composition of the PUx/CBm/NaCln membranes on the performance of the PUx/CBm/NaCln membrane-based evaporators was examined. the membranes with x being were As with an increase in PEG content, the hydrophilicity of PUx the membrane-based evaporators were floating on the water, the membrane water content increased with PEG content of PUx (Figure By an increase in PUx hydrophilicity hindered water flow the membrane, the water flux of the membrane as the PEG content Notably, with an increase in the PEG content, the water evaporation rate of the membrane-based evaporators increased and then water content and water flux of and kg m−2 h−1, the water evaporation rate reached a of 1.68 kg m−2 h−1 (Figure Next, the water evaporation rates of the membrane-based evaporators were (Figure As the NaCl content was increased, the water content and water flux of the membrane This was as increased NaCl content increased the membrane porosity ( Supporting Information Figure with an increase in water content and water a NaCl to PU20 mass ratio of the PU20/CB0.5/NaCl5 membrane-based evaporator exhibited the water evaporation Finally, the of the CB content on the performance of the membrane-based evaporators was (Figure We observed that the PU20/CB0.5/NaCl5 membrane exhibited the water content and water confirming that the PU20/CB0.5/NaCl5 membrane-based evaporator the water evaporation This is at an low CB content, the in the resulting membrane ( Supporting Information Figure thereby leading to a in porosity ( Supporting Information Figure water content, and water flux (Figure the other to its CB led to a in the water content and water flux of the membrane (Figure our that PU20 was the mass ratios of CB to PU20 and NaCl to PU20 were at and respectively, and the PU20/CB0.5/NaCl5 membrane-based evaporator exhibited the water evaporation rate of 1.68 kg m−2 Therefore, in the following study, the PU20/CB0.5/NaCl5 membranes were used to the self-healing solar-driven water evaporator. Figure 3 | Evaporation water and water content of the PUx/CBm/NaCln membrane as a of (a) the molar ratio of PEG, (b) the mass ratio of NaCl, and (c) the mass ratio of (d) changes of the simulated seawater and lake water with PU20/CB0.5/NaCl5 membrane-based evaporators under simulated solar light irradiation. Download figure Download PowerPoint The water evaporation rates of the PU20/CB0.5/NaCl5 membrane-based evaporator floating on lake water and simulated seawater from DI water, were examined. With the of the the evaporation rates of the lake water and simulated seawater were 1.67 and 1.61 kg m−2 h−1, (Figure The corresponding solar thermal conversion were and is a that all solar-driven evaporators seawater desalination. from the good of the PU20/CB0.5/NaCl5 membrane, the seawater evaporation rate of the PU20/CB0.5/NaCl5 membrane-based evaporator was at kg m−2 h−1 after h of seawater evaporation, which was times that of simulated seawater ( Supporting Information Figure Moreover, the seawater evaporation of the evaporator was recovered by 10 mL of seawater the PU20/CB0.5/NaCl5 membrane ( Supporting Information Figure These that the PU20/CB0.5/NaCl5 membranes potential in sewage purification and seawater desalination. the stability of the PU20/CB0.5/NaCl5 membranes was examined. We that the porosity of the PU20/CB0.5/NaCl5 membranes was after in and NaCl solutions for 10 indicating that the membranes exhibited satisfactory Moreover, the porosity of the PU20/CB0.5/NaCl5 membranes was well after placing in the or in water at 50 °C for 10 days ( Supporting Information Figure and Figure indicating that the porous structure in the membranes was highly These that the PU20/CB0.5/NaCl5 membranes good stability and could with the of solar-driven interfacial evaporators. Figure | changes of the PU20/CB0.5/NaCl5 membranes after being
The article discusses the V.V. Tselishchev’s original and unique systematic study of the specific and extremely complicated problems of Gödel results regarding the question of artificial intelligence essence. Tselishchev argues that the reflexive property should be considered not only as an advantage of human reasoning, but also as an objective internal limitation that appears in case of adding Gödel sentence to a theory to build a new theory. The article analyzes so-called mentalistic Gödel’s argument for fundamental superiority of human intelligence over machine one and the non-algorithmic nature of natural thinking. The discussion about the Gödel argument is not entirely speculative, but contains new knowledge. An example of such knowledge are the results of R. Smullyan levels of computers “awareness,” which are may be interpreted in a psychophysical sense. The concept of “zero level of intelligence” is proposed for such a reflexive property as “awareness of selfconsciousness.” Reflexive ranks below the awareness of self-consciousness can be considered negative levels of thinking in the sense that the intelligence, being reduced to them, significantly loses its completeness. Even self-consciousness turns out to be a negative level of thinking, since, according to Smullyan, the subject of self-consciousness is unaware of the type of thought to which he belongs. A thought experiment is proposed that allows us to establish the distribution of the properties of Smullyan stability and normality and to answer the question “Does an intuitive belief in the truth of a formal proof affect the truth of a proposition being proved?” According to intuitionism, the most unpleasant epistemic property is instability: beliefs that are not based on deep intuitions have no value. According to the constructivist philosophy of mathematics, instability is a less negative property than abnormality: the fact that high-ranking beliefs cannot be immersed to the very foundations is not significant because violation of truth due to lowering the rank of reflection is not critical.
We describe a fast three-round mutual authentication protocol for parties A and B belonging to the same coalition group. Parties A and B keep their own independent long-term private keys that are used in the process of authentication and can be used for other purposes. The scheme assumes an initial setup with a trusted third party T. This party initiates another secret information that includes factors of a large RSA modulus. For authentication, both parties must demonstrate each other the knowledge of their private keys without revealing them and the ability to factorize a large RSA modulus. Thus, the protocol based on the suggested scheme provides reciprocal authentication. The scheme possesses all desirable properties of an interactive proof, i.e., completeness, soundness, and zero-knowledge. The security of the protocol relies on assumptions of difficulty of the RSA factorization and existence of a cryptographic hash function.
Ulrich Haböck, Alberto Garoffolo, Daniele Di Benedetto
This document describes Darlin, a succinct zero-knowledge argument of knowledge based on the Marlin SNARK (Chiesa et al., Eurocrypt 2020) and the `dlog' polynomial commitment scheme from Bootle et al. EUROCRYPT 2016. Darlin addresses recursive proofs by integrating the amortization technique from Halo (IACR eprint 2019/099) for the non-succinct parts of the dlog verifier, and we adapt their strategy for bivariate circuit encoding polynomials to aggregate Marlin's inner sumchecks across the nodes the recursive scheme. We estimate the performance impact of inner sumcheck aggregation by about 30% in a tree-like scheme of in-degree 2, and beyond when applied to linear recursion.
Lukas Burkhalter, Hidde Lycklama, Alexander Viand, Nicolas Küchler · 5 authors
Federated Learning is an emerging decentralized machine learning paradigm that allows a large number of clients to train a joint model without the need to share their private data. Participants instead only share ephemeral updates necessary to train the model. To ensure the confidentiality of the client updates, Federated Learning systems employ secure aggregation; clients encrypt their gradient updates, and only the aggregated model is revealed to the server. Achieving this level of data protection, however, presents new challenges to the robustness of Federated Learning, i.e., the ability to tolerate failures and attacks. Unfortunately, in this setting, a malicious client can now easily exert influence on the model behavior without being detected. As Federated Learning is being deployed in practice in a range of sensitive applications, its robustness is growing in importance. In this paper, we take a step towards understanding and improving the robustness of secure Federated Learning. We start this paper with a systematic study that evaluates and analyzes existing attack vectors and discusses potential defenses and assesses their effectiveness. We then present RoFL, a secure Federated Learning system that improves robustness against malicious clients through input checks on the encrypted model updates. RoFL extends Federated Learning's secure aggregation protocol to allow expressing a variety of properties and constraints on model updates using zero-knowledge proofs. To enable RoFL to scale to typical Federated Learning settings, we introduce several ML and cryptographic optimizations specific to Federated Learning. We implement and evaluate a prototype of RoFL and show that realistic ML models can be trained in a reasonable time while improving robustness.
This perspectives article surveys the most promising privacy-preserving cryptographic technologies including secure multiparty computation, zero-knowledge proofs and fully homomorphic encryption, and their various real-world applications.
You are a humanities scholar and you are worried. You fear that the humanities are increasingly seen as irrelevant, unnecessary and quaint. You may even have begun to internalise this view. In the face of intractable contemporary problems – global pandemics, economic crisis and a climate emergency – how can your work seem like anything other than an indulgence? You hear the constant, ambient noise of public and political hostility aimed at what you do. In January 2020 the prime minister’s chief adviser, Dominic Cummings (a humanities graduate, like the prime minister), wrote a long blog post calling for ‘weirdos and misfits with odd skills’ to apply for new jobs at No. 10 Downing Street. He made it clear that he was looking for data scientists, software developers, economists and policy experts, not ‘Oxbridge English graduates who chat about Lacan at dinner parties with TV producers’.11 Dominic Cummings, ‘Two Hands are a Lot’, at https://dominiccummings.com/2020/01/02/two-hands-are-a-lot-were-hiring-data-scientists-project-managers-policy-experts-assorted-weirdos/ (2 January 2020, accessed 1 May 2020). Later that month the University of Sunderland announced that it would be shutting down its history, languages and politics courses, and replacing them with more ‘career-focused and professions-facing’ alternatives. In February the University of Portsmouth revealed plans to make more than half its English department redundant, citing the declining number of applications in this subject. In June 2020 the Australian education minister, Dan Tehan, announced that his government wanted to double student fees for courses in the arts and humanities while cutting them for nursing, agriculture, maths, science and information technology. The aim was ‘to power our post-Covid economic recovery’ by sending out a ‘price signal’ to encourage people to study in areas of growth.22 ‘Job-Ready Graduates to Power Economic Recovery’, at https://ministers.dese.gov.au/tehan/job-ready-graduates-power-economic-recovery (accessed 25 June 2020). The UK government made similar noises about pricing mechanisms and ending funding for humanities courses considered poor value for money. In August 2020 the A-level marking controversy, and the subsequent scramble for university places, inspired much media comment about the glut of worthless degrees in second-rate institutions, again focusing on humanities subjects. ‘The universities are churning out far more graduates than our society requires,’ wrote one columnist, ‘particularly in subjects like the creative arts and communications that have little relevance to the workplace.’33 Leo McKinstry, ‘We Must End This Absurd Obsession to Gain a Degree’, Daily Express, 20 August 2020. See also Emma Duncan, ‘Many Degrees are a Waste of Time and Money’, The Times, 15 August 2020. The current right-wing critique of universities as indoctrination camps where students are ‘factory-farmed to have the same boring and malevolent views’ has focused its ire on humanities subjects.44 Douglas Murray, ‘Our Universities Have Become Indoctrination Camps’, Sunday Telegraph, 16 August 2020. No wonder that, after reading these signs and portents, you feel beleaguered and dispirited. You crave some encouragement and cheer, and a reminder of why you first fell in love with the texts you spend your life examining. You need a story that will convince others, and yourself, of the worth of your work. You may take heart from the knowledge that, while this particular crisis is new, the issues are old. ‘The humanities are at the cross-roads, at a crisis in their existence,’ the historian J.H. Plumb wrote in the introduction to his Pelican edited collection, Crisis in the Humanities, in 1964. ‘They must either change the image that they present, adapt themselves to the needs of a society dominated by science and technology, or retreat into social triviality.’55 J.H. Plumb, ‘Introduction’, in Plumb (ed.), Crisis in the Humanities (Harmondsworth: Penguin, 1964), 8. This permanent crisis of identity and legitimacy in the humanities arises partly out of definitional fuzziness. The humanities have often been defined against something else – and against which they can be found wanting. In the Renaissance the studia humanitatis were the secular subjects, such as rhetoric, philosophy and ancient Greek and Latin, and thus the opposite of the highest form of study, divinity. Then, from the mid-nineteenth century onwards, the humanities began to be defined in opposition to the physical sciences. At first they were the senior partner. Charles Darwin’s frequent biblical and literary allusions, and the elegance of his own writing, show how influenced he was by the humanities. But in the century after Darwin’s death, the sciences grew in confidence and prestige. The main character in Saul Bellow’s 1987 novel More Die of Heartbreak, a Russian literature specialist, feels as if he has been confined to ‘the nursery games of humankind, which had to be left behind when the age of science began’. The humanities, he thinks gloomily, ‘would be called upon to choose a wallpaper for the crypt, as the end drew near’.66 Saul Bellow, More Die of Heartbreak (London: Penguin, [1987] 2004), 239. More recently, the humanities have come to seem like the poor relation of STEM. STEM is an acronym now routinely repurposed as both noun and adjective (STEM skills, STEM subjects, STEM jobs). We forget how new the acronym is and sometimes even what it stands for (science, technology, engineering and mathematics). The OED gives its earliest mention in print as 1968 but notes that it is ‘rare before 21st cent.’ In fact it began to be used widely in the US in the late 1990s, in debates about skills shortages in high-tech jobs and access to work visas for immigrants skilled in these fields. In Britain it has become an article of faith among policy makers that investing in STEM is vital to economic growth, especially in areas like life sciences, pharmaceuticals, computer coding and electronic engineering. 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and In The of the of noise as this of its that it on have become signs that something is out of the of noise and at the he The noise to – as if it were that it if it were not to be the of The of they are used more has little in the power of its to and change how are seen as a for out something for their of – as were a of on the of and not that The humanities scholar that are not a but the that the of that the is partly This them to be of current of and of other life can be it can be We have come to of reading as a a of a and the take something to something in its first the English to or the of The humanities reading in but a ‘The of an June in the humanities to come with our own and reading of a reading is it can be a but must be inspired by and into other and be to its In the humanities is a number of by from its to of the or that can be or at that can be the of to from its in of what called a University in the one first of with began to an to that of and a of to his of with a he not 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Intuitively there is a drastic distinction between the pure decentralized block-chain systems like Defis and those that only utilize block-chain as an enhancing technology but remain centralized with real-world business model and conventional technologies like database, application server, etc. Our study explores extensively this distinction from a methodological point of view, classifies them into blockchain-complete and blockchain-partial, analyzes key features of the two types, and reveals the root cause of this distinction. We analyze the function or, in more strong words, the "ultimate purpose" of blockchain in the blockchain-partial systems, and present a conceptual model we named proof-chain that quite satisfactorily represented the general paradigm of blockchain in blockchain-partial systems. A universal tension between strength of proof-chain and privacy is then revealed and the zero-knowledge based proof-chain takes shape. Several case studies demonstrate the explaining power of our proof-chain methodology. We then apply proof-chain methodology to the analysis of the ecosystem of a collaborating group of blockchain-partial systems, representing the paradigm of public and private data domain whose border the proof-chain crosses. Finally, some derived guidelines from this methodology speak usefulness of our methodology.
Nonogram is a pencil puzzle consisting of a rectangular white grid where the player has to paint some cells black according to given constraints. In 2010, Chien and Hon constructed a physical card-based zero-knowledge proof protocol for Nonogram, which enables a prover to physically show that he/she knows a solution of the puzzle without revealing it. However, their protocol requires special tools such as scratch-off cards and a sealing machine, making it impractical to implement in real world. The protocol also has a nonzero soundness error. In this paper, we develop a more practical card-based protocol for Nonogram with perfect soundness that uses only regular paper cards. We also show how to modify our protocol to make it support Nonogram Color, a generalization of Nonogram where the player has to paint the cells with multiple colors.
In the United Kingdom, at the outbreak of the COVID-19 pandemic in March 2020, the national health service (NHS) took the unprecedented step of restructuring all of its services and workforce to cope with the expected influx of infected patients.1 Following a UK-wide lockdown and implementation of strict government guidelines, rates of COVID-19 infection reduced significantly and there was hope of a return to normal practice. However, the risks of exposure to the Sars-Cov2 virus to patients and healthcare staff remained. These risks were acutely felt amongst otolaryngologists due to the prevalence of the virus in the nose and throat in both symptomatic and asymptomatic patients.2 A significant number of extra measures and precautions were introduced to mitigate the potential spread of the virus amongst patients and healthcare staff during surgery. This was predicted to reduce the efficiency of surgical lists and limit the ability of departments to clear the backlog of patients awaiting surgery.3 The aim of this study was to investigate whether elective otolaryngology surgical services could return to pre-pandemic levels in an area where cases of COVID-19 infection were expected to, and indeed did, remain far below national rates. Retrospective and prospective data were collected for all fixed-term otolaryngology consultants at a single rural hospital during the period of 1 August-28 February for 2019/20 and 2020/21. Data recorded included number of theatre lists, number of planned (PLO) and performed operations (PFO), number of cancellations and reasons for cancellation. Data were also collected regarding the number of COVID-19 infections per week during 2020/21 at local and national levels. Statistical analysis was performed using SPSS statistical software and Chi-squared testing was used to compare categorical data. Our hospital trust covers a population of approximately 235 000 people with a population density of 8 people/Km2. The department normally performs approximately 1500 operations per year. Over the 2-year period, there were three substantive consultants performing surgery in the following sub-specialties: Otology, Rhinology, General ENT, General Paediatric ENT, Paediatric airway and Thyroid and Parathyroid surgery. The department also provides facial plastics services for the removal of all benign and malignant skin lesions from the head and neck under local anaesthetic. All surgical lists were planned and booked in advance by the operating consultant. At the beginning of August 2020, all ENT elective surgery was allowed to restart. New hospital protocols were introduced for all elective procedures under general anaesthetic (GA). These included patient shielding for a minimum of 2 weeks prior to surgery, a negative COVID-19 PCR test, mandatory FFP3 masks for all aerosol-generating procedures (AGPs) and fallow time following extubation. Our primary objective was to see whether normal ENT elective services could restart to pre-pandemic levels; this was interrupted by a surge in COVID-19 infections in December 2020 as all non-urgent surgery was cancelled. We therefore analysed the period 1 August-30 November (interwave recovery [IR]) and the period 1 December-28 February (second wave [SW]) with the previous year. There were zero cases of COVID-19 infection reported locally or nationally in August-February 2019/20. In 2020/21, there were 2949 cases of COVID-19 infection in our local authority area.4 This represents 0.07% of the 3 868 809 cases reported in the United Kingdom over the same period.5 The trend in the 7-day positive rate during this period at local and national levels is demonstrated in the graph (Figure 1). From 1 August 2019 to 28 February 2020, there were 123 planned theatre sessions compared to 111 in 2020/21 with the number of operations planned dropping from 4.5 to 4.1 per session. The total numbers of PLO, PFO and local anaesthetic skin procedures (LASP) are demonstrated in Table 1. In the year prior to COVID-19, 81% of PLO were performed and this was 9% higher than the second year, and this falls to a 5% decrease during the IR period. Overall, there was a 31.2% reduction in the number of PFO, and again, this falls in the IR to a 4.1% (144 vs. 138) decrease year on year. However, there were 1.8 operations performed per session during the IR in 2020/21 compared to 2.2 in 2019/20. There was a significant increase in the number of local anaesthetic skin procedures (LASP) in 2020/21 (p ≤ .00001) and this accounted for 27% of PFO in the IR compared to 6% the previous year. If we exclude LASP, there was a 26.1% decrease in the number of GA procedures performed between August and November year on year. There was a significant increase in the number of cancelled operations in 2020/21 compared to 2019/20 (p = .011); however, during August-November, there was no significant increase (p = .259). In 2019/20, 19% of PLO were cancelled compared to 28.3% in 2020/21. This percentage drops when analysing the IR (22%) to the same period in 2019/20 (17%). Overall, this represents a 15.5% increase in the number of cancellations and equates to a cancellation every 1.8 operational sessions; however, during the IR, this relates to a cancellation every 2.0 operational sessions. The reasons for cancelled operations are categorised and are shown in Figure 2. Our study shows that there has been a change in ENT elective surgical provision at our hospital since its re-introduction. It is unclear why fewer procedures were planned per list in 2020/21, but may possibly represent the expected delays caused by changes in standard operating procedures in response to the pandemic. These changes have been seen globally with the introduction of donning and doffing of personal protective equipment (PPE), the adaptation of theatres to protect essential apparatus from contamination and the refinement of surgical techniques to reduce the risk of transmission.6 The 31.2% reduction in PFO during 2020/21 can be mainly attributed to the second wave and the cancellation of all non-urgent surgery from the end of December 2020. During the IR period, there was a 4.1% decrease in PFO; however, on a per-session basis, this equates to an 18.1% reduction. This suggests that during periods of low community COVID-19 transmission, elective services are still unable to return to pre-pandemic levels. The reasons for this are likely multifactorial; however, the impact of wearing PPE during surgery cannot be underestimated, as it is known to affect surgical performance and non-technical skills.7 The return of near-normal operating surgical volume during the IR period may be explained by the significant increase in the number of LASP, as this accounted for 27% of all PFO. This significant increase (p ≤ .00001) is important as without LASP, the number of PFO would likely have dropped further, as LASP were not required to isolate pre-operatively or undergo covid-19 PCR testing as were not deemed AGPs. Consequently, last-minute vacancies left by cancellations could be filled at short notice. We found a significant increase in the number of operations cancelled in 2020/21 (p = .011). This was expected with a surge of COVID-19 during the winter months, as there was no significant increase in cancellations seen between August and November. We can therefore assume that during periods of low community transmission, hospital capacity is not affected and patients are willing to undergo surgery despite the extra safety and shielding requirements. Despite low numbers of community infections, necessary safety protocols have reduced the efficiency of surgical lists and their ability to adapt to change. The current NHS elective waiting list currently stands at over 4.5 million patients8 and previous studies have estimated that clearing a backlog of cases created by the pandemic may take 84 weeks, but this assumes activity returning at 110% of pre-pandemic levels.9 Our study suggests that this level of activity would be difficult to attain in otolaryngology and therefore we would expect clearance of waiting lists to take significantly longer. We suggest extensive triaging of patients on long waiting lists to ensure that procedures are still clinically indicated, as it is likely that in some cases, such as otitis media with effusion, criteria for intervention may no longer be met. However, we recognise that sufficient time will need to be provided to clinicians in order to facilitate this effectively. Surgical trainees across all specialties have been adversely affected by the pandemic with a significant reduction in operative experience and a greater than 50% reduction in logbook numbers.10 This has resulted in GMC-approved curriculum derogations by the joint committee on surgical training (JCST) to enable the progression of trainees at all levels.11 Our study has demonstrated that a rapid return to pre-pandemic activity is unlikely in the near-term even as rates of COVID-19 infection fall following a successful vaccination programme. The challenges trainees have faced in gaining sufficient operative experience will likely continue, although improve from present. This is important to acknowledge, as it will have implications for trainees attaining Certification of Completion of Training (CCT) this year and in the future. The study has its limitations. A lower-than-average number of COVID-19 cases cannot be assumed to have had less of an impact on the hospital providing ENT elective services. A smaller population and a smaller number of hospital beds available would mean even small increase in the 7-day positive rate could potentially impact the hospital's ability to provide elective surgery. Due to a lack of full-time substantive consultants, we were only able to compare a small number directly year to year. Our hospital was also without a full-time head & neck consultant during the second year and this meant sending patients to other centres in order to facilitate their care. The policies and guidelines implemented prior to restarting elective surgery were based on the best practice at that time and may not reflect advances in knowledge and the impact vaccination may have on future elective services. Low rates of COVID-19 infection do not necessarily mean that ENT elective services can return to pre-COVID levels. Implementation of new safety protocols to protect patients and staff has reduced the efficiency and speed at which elective ENT surgery can be delivered. This is likely to continue to impact waiting lists at a time when surgical activity is needed to exceed pre-pandemic levels. It is likely that workloads will increase, as extra theatre lists become more commonplace; however, in order to clear the backlog, NHS trusts will need to become more innovative in their approach. None. This study took the form of an audit, so National Research Ethics Service approval was not required. The local audit department approved the study. Sam Arman: Project lead involved with design, data collection and data analysis. Michael Hopkins: Involved with data analysis, editing and proofing final submission. Simon McKean: Project supervisor, involved with editing final publication None.
This paper introduces a blockchain-based federated learning (FL) framework with incentives for participating nodes to enhance the accuracy of classification problems. Machine learning technology has been rapidly developed and changed from a global perspective for the past few years. The FL framework is based on the Ethereum blockchain and creates an autonomous ecosystem, where nodes compete to improve the accuracy of classification problems. With privacy being one of the biggest concerns, FL makes use of the blockchain-based approach to ensure privacy and security. Another important technology that underlies the FL framework is zero-knowledge proofs (ZKPs), which ensure that data uploaded to the network are accurate and private. Basically, ZKPs allow nodes to compete fairly by only submitting accurate models to the parameter server and get rewarded for that. We have conducted an analysis and found that ZKPs can help improve the accuracy of models submitted to the parameter server and facilitate the honest participation of all nodes in FL.
E-Commerce has become more and more popular because of rich products, fast transactions, and free from time, locations, stores, and so on. However, the disclosure of personal data such as their IDs, addresses, and phone numbers has become a major concern for online activities. The current e-commerce model is at the crossroads of ownership and privacy. To address this, this article creates an enterprise protocol that uses smart personal contracts to protect privacy during the negotiation phase. This protocol allows contracting parties to conduct business without disclosing personal information such as identity, address, and phone number. Furthermore, we employ the zero-knowledge proof to ensure ownership.
Quantum computing is no longer a thing of the future. Shor’s algorithm proved that a quantum computer couldtraverse key of factoring problems in polynomial time. Because the time-complexity of the exhaustive keysearch for quantum computing has not reliably exceeded the reasonable expiry of crypto key validity, it is believedthat current cryptography systems built on top of computational security are not quantum-safe. Quantumkey distribution fundamentally solves the problem of eavesdropping; nevertheless, it requires quantumpreparatory work and quantum-network infrastructure, and these remain unrealistic with classical computers.In transitioning to a mature quantum world, developing a quantum-resistant mechanism becomes a stringentproblem. In this research, we innovatively tackled this challenge using a non-computational difficulty schemewith zero-knowledge proof in order to achieve repellency against quantum computing cryptanalysis attacks foruniversal classical clients.
In a seminal work, Goldreich, Micali and Wigderson (CRYPTO ’86) demonstrated the wide applicability of zero-knowledge proofs by constructing such a proof system for the NP-complete problem of graph 3-coloring. A long-standing open question has been whether parallel repetition of their protocol preserves zero knowledge. In this work, we answer this question in the negative, assuming a standard cryptographic assumption (i.e., the hardness of learning with errors (LWE)).
Cherlina Helena Purnamasari Panjaitan, Lisda Juliana Pangaribuan
Protocol Zero Knowledge Proof is one of the protocols in Cryptography that has a fairly good level of security, because it applies the concept of "Truly Zero Knowledge Proof" which is not leaking any information. This protocol is used in the Fiat Shamir, Guillou Quisquater and Schnorr Feige Algorithms, all of which are Cryptographic Algorithms using private keys and public keys. In the Public key, all three of these Algorithms use a random number generator at the values p and q to get the public key. In this study, the author will generate a public key generation test using CPRNG (Cryptographically-secure Pseudo-Random Number Generator) with the Blum Blum Shub algorithm. The test will be conducted on the Fiat Feige Algorithm, the formation of the key will use the Blum Blum Shub Algorithm, but the Identification Protocol still uses the Fiat Shamir Feige Algorithm. The results of this study show the Feige Fiat Algorithm with the Blum Blum Shub Algorithm as the key builder successfully identifies the pattern sent by the signer.
Purchases of electric vehicles have been increasing in recent years. These vehicles differ from traditional fossil-fuel-based vehicles especially in the time consumed to keep them running. Electric-Vehicle-charging Service Providers (EVSPs) must arrange reasonable charging times for users in advance. Most EVSP services are based on third-party platforms, but reliance on third-party platforms creates a lack of security, leaving users vulnerable to attacks and user-privacy leakages. In this paper, we propose an anonymous blockchain-based system for charging-connected electric vehicles that eliminates third-party platforms through blockchain technology and the establishment of a multi-party security system between electric vehicles and EVSPs. In our proposed system, digital certificates are obtained by completing distributed Public Key Infrastructure (distributed-PKI) identity registration, with the user registration kept separate from the verification process, which eliminates dependence on the EVSP for information security. In the verification process, we adopt smart contracts to solve problems associated with centralized verification and opaque services. Furthermore, we utilize zero-knowledge proof and ring-signature superposition to realize completely anonymous verification, which ensures undeniability and unforgeability with no detriment to anonymity. The evaluation results show that the user anonymity, information authenticity, and system security of our system fulfill the necessary requirements.
Essence and Existence: Selected Essays brings together fifteen essays by Bob Hale, mostly written between the publication of his last book, Necessary Beings, in 2013 and his death in 2017 from cancer, which he had been battling for some time. Six of the essays are published here for the first time, several of the remaining ones are not easily accessible, and there is a complete bibliography of Hale’s writings. The collection is carefully edited by Hale’s former student Jessica Leech, who has contributed some useful editorial notes detailing the editorial changes made to the manuscripts that Hale did not have time to complete entirely. The book contains an eight-page introduction by Kit Fine, which combines some touching personal reminiscences with a very useful critical discussion of two of the included essays, which are concerned with truthmaker semantics for universal generalizations and for modal statements. As will be no surprise to readers familiar with Hale’s work, the essays cover a wide range of topics: from truthmaker semantics, through modality and ontology, to logic and the philosophy of mathematics. My discussion will focus on the essays that deal with, or bear on, the philosophy of mathematics. Some of these essays — eight of the total fifteen — are useful further developments of themes that will be familiar to readers of Hale, while others introduce entirely new themes. A clear example of the latter is the new essay ‘What makes true universal statements true?’, which also benefits from a critical analysis in Fine’s introduction. Nearly all extant truthmaker semantics take a universal generalization to be made true by a state composed of states that verify each of the instances of the generalization. Hale concedes that this standard account seems correct of some generalizations, e.g., that all of his children live in England. But he insists that the standard account is incorrect of other generalizations, e.g., that every natural number has a successor. Perhaps most importantly, the standard account fails to do justice to an ‘obvious uniformity in the grounds for the truth of the instances’ (p. 107). It is far more plausible, Hale contends, that the generalization is made true by the essence or nature of the property of being a natural number, namely, that it lies in the nature of this property that every instance has a successor. On Hale’s view, then, universal generalizations can have two entirely different kinds of truthmakers. In addition to the instantial truthmakers invoked by the standard account, there are generic ones, where ‘a single state which has no proper parts’ (p. 114) verifies a universal generalization, along with each of its instances. These philosophical ideas are potentially very fertile in the philosophy of mathematics. In particular, generic truthmakers can be seen as a more abstract and general analogue of the intuitionistic conception of universal generality, thus making a version of this conception available even to philosophers who reject the more problematic aspects of intuitionism. To spell things out technically, Hale sketches a truthmaker semantics that permits a single non-composite state to verify a universal generalization directly, and where such generic verifiers are allowed to coexist with the usual composite verifiers invoked by the standard account. While this is a good start, the semantics has some undesirable features, as Fine points out. In particular, the semantics is unabashedly non-compositional, because the verifiers and falsifiers of a universal generalization need have no connection with those of its subformulas. Moreover, Hale’s motivating ideas are compatible with many different choices when setting up a truthmaker semantics. One must therefore be extremely wary of drawing strong consequences from the particular semantics that Hale sketches. In particular, it seems to me a wide open question whether the motivating ideas are best explicated by means of a semantics that validates classical logic (as Hale believes), as opposed to intuitionistic (as argued in unpublished work of mine that Hale criticizes in an appendix but regrettably conflates with a published article where the ideas are only briefly summarized). Another essay that breaks new ground is ‘Essence and definition by abstraction’ (2018), which is a valuable addition to the neo-Fregean program. Hume’s Principle, we recall, is the ‘abstraction principle’ stating that the number of |$F$|s is identical with the number of |$G$|s just in case the |$F$|s and the |$G$|s can be one-to-one correlated. This principle is often regarded as some form of definition of the number-of operator. What kind of definition might this be? As Hale observes, it would have to be an implicit definition, not an explicit one; for the principle affords no way to eliminate the definiendum. He also discusses where the definition might be located on the spectrum from stipulative to interpretative definitions — answering, in the spirit of Carnapian explications, ‘somewhere in the middle’. The heart of the essay, however, concerns a third axis of comparison, namely between what Locke called nomininal and real definitions. As Hale asks (p. 11), ‘what is the relation between Hume’s principle, taken as an implicit definition of the number operator […] and the essence or nature of the corresponding entities — the function from concepts or properties to objects, and those objects themselves, i.e., the cardinal numbers in general, and the natural numbers?’ The answer, Hale contends, is that abstraction involves a ‘coincidence of nominal with real essence’ (p. 15). If correct, this ‘coincidence’ promises a route to a priori knowledge of real definitions, namely that, in the relevant cases, ‘we fix essence by fixing meaning’ (p. 18). Why, though, should we believe in this happy match between nominal and real essence? Hale’s answer has two parts. First, he warns against a ‘false assimilation’ of abstraction principles ‘to cases in which we seek to capture the essence of natural kinds. Cardinal and natural numbers are not natural kinds — at least not in the same sense in which gold and tigers are. They are, as one might say, artificial kinds’ (p. 19). Second, Hale supports his view of definitions by appealing to the attractive neo-Fregean idea that numbers are ‘metaphysically lightweight’. The idea is that the existence of numbers ‘depends only upon there being properties which are one-one correlated’ (p. 19); and, as we shall see shortly, the needed properties too are taken to have a lightweight character. Clearly, this yields an ‘abundant conception’ of properties and abstracta (p. 20). Hale can now explain ‘how we achieve such a happy match between our definition and the essence’, namely because ‘given the abundant conception, we cannot very well miss the target’ (p. 21; italics original). Although the idea of metaphysically lightweight existence will no doubt strike many readers as elusive, Hale’s discussion thus reveals the potential for some entirely new theoretical benefits of the idea. ‘The problem of mathematical objects’ (2011) discusses a central question in the philosophy of mathematics, namely how we can know that there are infinitely many natural numbers. According to what Hale calls property-based approaches, ‘an infinite sequence of objects is seen as dependent on an underlying infinity of properties’. Unsurprisingly, he is particularly enamoured of the neo-Fregean version of this approach, where the existence of zero is derived from a property (such as non-self-identity) that necessarily has no instances, one is derived from the property of being identical with zero, and so on, following the famous Fregean bootstrapping argument. By contrast, object-based approaches argue directly that we have some form of access to at least a potential infinity of numbers (p. 213). Hale focuses on Charles Parsons’s [1980] account of mathematical intuition, which seeks to tie this form of intuition to ordinary perception and imagination. Parsons argues our ability to imagine an arbitrary sequence of strokes being extended gives us intuitive knowledge that every number has a successor, which in turn answers our central question. Hale is unconvinced. He takes Parsons’s account to require that we be able to imagine any given finite sequence of strokes. But this assumption seems questionable. Why can our imagination not enable us to grasp the operation of adding one stroke independently of our ability to imagine every argument of the operation, just as our perception enables us to grasp, say, the property of being red independently of our ability to perceive every instance of this property? To borrow terminology from Hale’s own discussion of universal generality, it seems more promising to understand the operation of adding one stroke in a generic, rather than an instantial, manner. Moreover, even if Hale’s criticism were upheld, his distinction between object-based and property-based approaches seems a red herring. For notice that the Fregean bootstrapping argument can be adapted to use pluralities of objects instead of properties. The only relevant difference between the two versions of the argument concerns our ability to obtain zero by abstraction. While there clearly are uninstantiated properties, the idea of an empty plurality is controversial. But even without an empty plurality, this wrinkle can be ironed out, say, by regarding the number-of operator as a ‘co-partial function’ (in the sense of [Oliver and Smiley, 2016, p. 88], which can have the value zero on an undefined argument. Thus, when classifying answers to the central question of how we can know that there are infinitely many numbers, what primarily matters is presumably whether an account relies on some form of Fregean bootstrapping, not whether we bootstrap on properties or (pluralities) of objects. In ‘Ordinals by abstraction’, published here for the first time, Hale discusses the thorny problem of ordinal abstraction — i.e., abstraction on well-ordered relations under the equivalence of isomorphism — whose naïve version falls prey to a version of the Burali-Forti paradox. First, he critically discusses a recent attempt by Ian Rumfitt [2018], based on restricting the second-order logic to so-called |$\Delta^1_1$|-comprehension. This solution would, however, have devastating consequences for other parts of the neo-Fregean program. Then, Hale attempts to develop a better solution, which is also more hospitable to the neo-Fregean agenda. In essence, his proposal is to restrict the abstraction to well-orderings that are in some sense ‘definite’. An interesting exploration of the desired notion of definiteness ensues, which opens promising avenues for further research, but stops short of presenting a worked-out theory of ordinals. A central theme of the collection to which three of its fifteen essays are devoted, is a broadly Fregean approach to properties. As I am the co-author of one of these essays, the previously unpublished ‘Ontological categories and the problem of expressibility’, I will only mention that its topic is how Fregeans can properly express their view that objects are denoted by singular terms, first-level properties by first-level predicates, and so on, without violating their own type-theoretic restrictions; and that the answer takes the form of a theory of nominalization, which allows higher-level properties to be denoted also by singular terms, albeit in a derivative manner. Thus, the essay builds on and extends the work of Hale and Wright [2012]. The other two essays in this category, ‘Second-order logic: Properties, semantics, and existential commitments’ (2015) and ‘Properties, predication, and arbitrary sets’ (previously unpublished), develop and defend the Fregean conception of properties that Hale first advocated in [Hale, 2013], Chapters 1 and 8. This conception postulates an extremely tight connection between a property and a suitable ‘predicate’ (or open formula) that expresses or characterizes the property. Indeed, Hale writes that ‘a necessary as well as sufficient condition [for the existence of a property] would require only that there could be a suitable predicate’ (p. 62). The sufficient condition makes property existence very undemanding: ‘the existence of a suitable predicate is sufficient for that of a property’ (p. 191). The result is an abundant conception of properties, not a scarce one where properties are required, say, to figure in scientific laws. As Hale observes, however, the necessary condition — that there could be a suitable predicate — is ‘far from toothless’ (p. 63). For ‘[b]y a predicate here, we mean an expression of finite length — an expression which we could, at least in principle, understand and use to speak of the property’ (p. 192). Hale’s conception of properties thus involves a form of definabilism. This is a highly distinctive conception, wedged in between two more familiar and well-developed ones. On the one hand, Hale’s conception is far more restrictive than the truly abundant set-theoretic conception, which takes properties to be — or at least to be adequately represented by — arbitrary sets of objects from the first-order domain. On the other hand, Hale goes to great lengths to emphasize two respects in which his form of definabilism is more liberal than traditional forms thereof, such as that of Weyl [1918]. First, there is no fixed language in which the ‘suitable predicates’ must be available. In particular, to insist on definability in the relevant object language would be ‘needlessly crippling’ (p. 194). Second, the predicates in question are allowed to be impredicative (i.e., to involve bound second-order variables). Has Hale succeeded in articulating a stable middle ground between the yet more liberal, set-theoretic conception and the more restrictive, predicative form of definabilism? Like any defender of an intermediate view, Hale faces a battle on two sides. On one flank, he will be attacked by defenders of the set-theoretic conception. A powerful such attack can be found in [Shapiro, 2018]. As Shapiro emphasizes, contemporary mathematics freely uses the axiom of choice and would be completely crippled without at least a weak form of this axiom. But definabilists are not entitled to this axiom, for the simple reason that the ‘choice set’ asserted to exist need not be definable. Hale’s dismissive response in ‘Properties, predicates, and arbitray sets’ is unlikely to satisfy any reader who is unwilling to sacrifice vast tracts of actual mathematics for purely philosophical reasons. On the opposite flank, Hale will be attacked by traditional definabilists, who will challenge both of his desired liberalizations. Let us begin with Hale’s attempt to go beyond definability in any particular language. ‘[T]he sense of definable in which the only properties there are are definable’, he writes, ‘is what we might call an absolute sense — definable in some language, actual or possible’ (p. 195). But the idea of such an absolute notion of definability is problematic. The standard notion of a definable set (or property) relies on a Tarskian notion of satisfaction, which is defined only relative to a particular language. Presumably, the desired absolute notion of definability would require an absolute notion of satisfaction, which is applicable not only to all actual languages but also any possible one. However, there is no reason to believe that such a notion exists. Here the burden of proof falls entirely on Hale, who seeks to go beyond standard definabilism, but fails to explain how the desired extension is supposed to work.1 Next, let |$\textrm{Def}(\mathbb{N})$| be the set of all first-order definable subsets of |$\mathbb{N}$|. Let us now consider the second-order model obtained from |$\mathcal{N}$| by letting |$\textrm{Def}(\mathbb{N})$| be the second-order domain. It is easy to verify that this is a model of second-order arithmetic with only predicative comprehension.2 The important thing to notice is that this model is obtained through a sequence of perfectly good mathematical definitions, without any reliance on the powerset operation. With this review of definability in place, let us now follow Hale and try to define the second-order domain as the set |$D$| of all and only the subsets of the natural numbers that are definable by means of any second-order formula, including impredicative ones. The circularity of this attempted definition is now apparent. Any talk about definability by means of a second-order formula presupposes a second-order domain, which is precisely what we are attempting to define. Hale has, as it were, given us an equation with an unknown |$D$|. If this equation has a unique solution, we would at least have an implicit definition of the second-order domain. But does Hale’s equation have a unique solution, rather than none or more than one? Sam Roberts and Kameryn Williams have each proved that the answer turns out to be ‘more than one’.3 This is terrible news for Hale: not only is his attempted definition of the second-order domain circular, but it remains unsuccessful even when viewed as a implicit definition. I conclude that we lack any kind of worked-out model of Hale’s attempted conception of properties, leaving it doubtful whether there is a coherent conception here at all. To sum up, the book is full of interesting and often promising ideas. Some of these ideas need to be more fully developed, however, and at least one central idea, I have argued, is unlikely to admit of any such development. It is a shame that Hale is no longer with us to continue the discussion, which he would no doubt have done with insight as well as passion.
Jung Hee Cheon, Dongwoo Kim, Duhyeong Kim, Keewoo Lee
The scaled inverse of a nonzero element $a(x)\in \mathbb{Z}[x]/f(x)$, where $f(x)$ is an irreducible polynomial over $\mathbb{Z}$, is the element $b(x)\in \mathbb{Z}[x]/f(x)$ such that $a(x)b(x)=c \pmod{f(x)}$ for the smallest possible positive integer scale $c$. In this paper, we investigate the scaled inverse of $(x^i-x^j)$ modulo cyclotomic polynomial of the form $Φ_{p^s}(x)$ or $Φ_{p^s q^t}(x)$, where $p, q$ are primes with $p<q$ and $s, t$ are positive integers. Our main results are that the coefficient size of the scaled inverse of $(x^i-x^j)$ is bounded by $p-1$ with the scale $p$ modulo $Φ_{p^s}(x)$, and is bounded by $q-1$ with the scale not greater than $q$ modulo $Φ_{p^s q^t}(x)$. Previously, the analogous result on cyclotomic polynomials of the form $Φ_{2^n}(x)$ gave rise to many lattice-based cryptosystems, especially, zero-knowledge proofs. Our result provides more flexible choice of cyclotomic polynomials in such cryptosystems. Along the way of proving the theorems, we also prove several properties of $\{x^k\}_{k\in\mathbb{Z}}$ in $\mathbb{Z}[x]/Φ_{pq}(x)$ which might be of independent interest.
Jung Hee Cheon, Dongwoo Kim, Duhyeong Kim, Keewoo Lee
The scaled inverse of a nonzero element $a(x)\in \mathbb{Z}[x]/f(x)$, where $f(x)$ is an irreducible polynomial over $\mathbb{Z}$, is the element $b(x)\in \mathbb{Z}[x]/f(x)$ such that $a(x)b(x)=c \pmod{f(x)}$ for the smallest possible positive integer scale $c$. In this paper, we investigate the scaled inverse of $(x^i-x^j)$ modulo cyclotomic polynomial of the form $\Phi_{p^s}(x)$ or $\Phi_{p^s q^t}(x)$, where $p, q$ are primes with $p<q$ and $s, t$ are positive integers. Our main results are that the coefficient size of the scaled inverse of $(x^i-x^j)$ is bounded by $p-1$ with the scale $p$ modulo $\Phi_{p^s}(x)$, and is bounded by $q-1$ with the scale not greater than $q$ modulo $\Phi_{p^s q^t}(x)$. Previously, the analogous result on cyclotomic polynomials of the form $\Phi_{2^n}(x)$ gave rise to many lattice-based cryptosystems, especially, zero-knowledge proofs. Our result provides more flexible choice of cyclotomic polynomials in such cryptosystems. Along the way of proving the theorems, we also prove several properties of $\{x^k\}_{k\in\mathbb{Z}}$ in $\mathbb{Z}[x]/\Phi_{pq}(x)$ which might be of independent interest.