Many existing anonymous parking payment schemes lack high efficiency and flexibility. For instance, the calculation and communication costs involved in payment may linearly increase with the payment amount. In this paper, we propose an anonymous payment system (dubbed AnoPay) for vehicle parking, which leverages updatable attribute-based anonymous credentials and efficient zero-knowledge proof (ZKP) to achieve user anonymity and constant overhead for parking fee payment. To further improve the efficiency, we design a secure parking fee aggregation protocol based on linear homomorphic encryption to aggregate parking transactions, where the amount of each parking transaction is hidden and the privacy of the parking lot in terms of its revenue is guaranteed. AnoPay achieves both unlinkability and accountability, malicious payments can be efficiently traced when it is necessary. We provide a security model and rigorous proof for each security property of AnoPay. Extensive experiments and comparisons demonstrate the efficiency and practicality of the system.
Dominic Grandjean, Lioba Heimbach, Roger Wattenhofer
In September 2022, Ethereum transitioned from Proof-of-Work (PoW) to Proof-of-Stake (PoS) during "the merge" - making it the largest PoS cryptocurrency in terms of market capitalization. With this work, we present a comprehensive measurement study of the current state of the Ethereum PoS consensus layer on the beacon chain. We perform a longitudinal study of the history of the beacon chain. Our work finds that all dips in network participation are caused by network upgrades, issues with major consensus clients, or issues with service operators controlling a large number of validators. Further, our longitudinal staking power decentralization analysis reveals that Ethereum PoS fairs similarly to its PoW counterpart in terms of decentralization and exhibits the immense impact of (liquid) staking services on staking power decentralization. Finally, we highlight the heightened security concerns in Ethereum PoS caused by high degrees of centralization.
Motivated by new applications such as secure Multi-Party Computation (MPC), Fully Homomorphic Encryption (FHE), and Zero-Knowledge proofs (ZK), many MPC-, FHE- and ZK-friendly symmetric-key primitives that minimize the< number of multiplications over Fp for a large prime p have been recently proposed in the literature. These symmetric primitives are usually defined via invertible functions, including (i) Feistel and Lai-Massey schemes and (ii) SPN constructions instantiated with invertible non-linear S-Boxes. However, the “invertibility” property is actually never required in any of the mentioned applications.In this paper, we discuss the possibility to set up MPC-/FHE-/ZK-friendly symmetric primitives instantiated with non-invertible bounded surjective functions. In contrast to one-to-one functions, each output of a l-bounded surjective function admits at most l pre-images. The simplest example is the square map x → x2 over Fp for a prime p ≥ 3, which is (obviously) 2-bounded surjective. When working over Fnp for n ≥ 2, we set up bounded surjective functions by re-considering the recent results proposed by Grassi, Onofri, Pedicini and Sozzi at FSE/ToSC 2022 as starting points. Given a quadratic local map F : Fmp → Fp for m ∈ {1, 2, 3}, they proved that the shift-invariant non-linear function over Fnp defined as SF (x0, x1, . . . , xn−1) = y0∥y1∥ . . . ∥yn−1 where yi := F(xi, xi+1) is never invertible for any n ≥ 2 · m − 1. Here, we prove that • the quadratic function F : Fmp → Fp for m ∈ {1, 2} that minimizes the probability of having a collision for SF over Fnp is of the form F(x0, x1) = x20 + x1 (or equivalent);• the function SF over Fnp defined as before via F(x0, x1) = x20 +x1 (or equivalent) is 2n-bounded surjective.As concrete applications, we propose modified versions of the MPC-friendly schemes MiMC, HadesMiMC, and (partially of) Hydra, and of the FHE-friendly schemes Masta, Pasta, and Rubato. By instantiating them with the bounded surjective quadratic functions proposed in this paper, we are able to improve the security and/or the performances in the target applications/protocols.
Modern blockchains supporting smart contracts implement a new form of state machine replication with a trusted and decentralized paradigm. However, inefficient smart contract transaction execution severely limits system throughput and hinders the further application of blockchain.
Tal Derei, Benjamin Aulenbach, Victor Carolino, Caleb Geren · 8 authors
Zero-Knowledge proofs are a cryptographic technique to reveal knowledge of information without revealing the information itself, thus enabling systems optimally to mix privacy and transparency, and, where needed, regulatability. Application domains include health and other enterprise data, financial systems such as central-bank digital currencies, and performance enhancement in blockchain systems. The challenge of zero-knowledge proofs is that, although they are computationally easy to verify, they are computationally hard to produce. This paper examines the scalability limits of leading zero-knowledge algorithms and addresses the use of parallel architectures to meet performance demands of applications.
Summary Every transaction is made public and verified by a third party, and the transparency of blockchain applications leads to privacy leaks. Everyone can access the transaction, making it easier for network analysis to identify the user's identity, which is a major problem with the blockchain. Financial institutions have become hesitant to adopt blockchain technology; as a result, preventing its spread. To confirm that encryption and security are maintained for transactions in the blockchain, this research introduces a zero‐knowledge proof (ZKP) based transaction validation scheme. To increase the security of blockchain applications, the proposed lattice‐based blind ring signature (LBRS) scheme integrates blind and ring signatures and is applied to sensitive data. The data are encrypted using this encryption scheme before being stored with the transactional information in the blocks. The encrypted data is then stored in the blocks, which users can retrieve after verification. The encrypted data is then stored in blocks, which users can retrieve after verification. A verification scheme based on the ZKP is used to prevent unauthorized access and changes to the data. The proposed LBRS scheme meets the security analysis requirement. The performance of an LBRS scheme is compared to other relevant models in terms of execution time, encryption time, and decryption time. Overall, the results are more encouraging and reassuring than other relevant works of interest. Finally, this model provides better computational security and satisfies the requirements like correctness and security analysis.
With natural language processing as an important research direction in deep learning, the problems of text similarity calculation, natural language inference, question and answer systems, and information retrieval can be regarded as text matching applications for different data and scenarios. Secure matching computation of text string patterns can solve the privacy protection problem in the fields of biological sequence analysis, keyword search, and database query. In this paper, we propose an Intelligent Semi-Honest System (ISHS) for secret matching against malicious adversaries. Firstly, a secure computation protocol based on the semi-honest model is designed for the secret matching of text strings, which adopts a new digital encoding method and an ECC encryption algorithm and can provide a solution for honest participants. The text string matching protocol under the malicious model which uses the cut-and-choose method and zero-knowledge proof is designed for resisting malicious behaviors that may be committed by malicious participants in the semi-honest protocol. The correctness and security of the protocol are analyzed, which is more efficient and has practical value compared with the existing algorithms. The secure text matching has important engineering applications.
Zero-knowledge proof is a critical cryptographic primitive. Its most practical type, called zero-knowledge Succinct Non-interactive ARgument of Knowledge (zkSNARK), has been deployed in various privacy-preserving applications such as cryptocurrencies and verifiable machine learning. Unfortunately, zkSNARK like Groth16 has a high overhead on its proof generation step, which consists of several time-consuming operations, including large-scale matrix-vector multiplication (MUL), number-theoretic transform (NTT), and multi-scalar multiplication (MSM). Therefore, this paper presents cuZK, an efficient GPU implementation of zkSNARK with the following three techniques to achieve high performance. First, we propose a new parallel MSM algorithm. This MSM algorithm achieves nearly perfect linear speedup over the Pippenger algorithm, a well-known serial MSM algorithm. Second, we parallelize the MUL operation. Along with our self-designed MSM scheme and well-studied NTT scheme, cuZK achieves the parallelization of all operations in the proof generation step. Third, cuZK reduces the latency overhead caused by CPU-GPU data transfer by 1) reducing redundant data transfer and 2) overlapping data transfer and device computation. The evaluation results show that our MSM module provides over 2.08x (up to 2.94x) speedup versus the state-of-the-art GPU implementation. cuZK achieves over 2.65x (up to 4.86x) speedup on standard benchmarks and 2.18× speedup on a GPU-accelerated cryptocurrency application, Filecoin.
Khaled Ahmed, Sabry F. Saraya, John F. Wanis, Hesham Ali
Open finance is evolving and extending open banking. This creates a large context that implies a financial and identity data exchange paradigm, which faces challenges to balance customer experience, security, and the self-control over personal identity information. We propose Self-Sovereign Banking Identity (SSBI), a Blockchain-based self-sovereign identity (SSI) to secure private data sharing by utilizing trusted customer’s banking cards as a key storage and identity transaction-signing enclave. The design and implementation of the SSI framework is based on the Veramo SDK and Ethereum to overcome the limitation of signing curve availability on the current banking Java Cards needed for Hyperledger Indy. SSBI uses the elliptic curve SECP256K1 for transaction signing, which exists for several payment cards in the market. SSBI enables automated financial services and trust in the service provider communication. This work analyzes the flow and framework components, and evaluates the usability, integration, and performance in terms of throughput, latency, security, and complexity. Furthermore, the proposed approach is compared with related solutions. The presented prototype implementation is based on a test Ethereum network and signing transactions on the banking card. The preliminary results show that SSBI provides an effective solution for integrating the customer’s banking cards to secure open banking identity exchange. Furthermore, it allows the integration of several scenarios to support trusted open banking. The Blockchain layer settings need to be scaled and improved before real-world implementation.
With the development of cloud services and the Internet of Things, the integration of heterogeneous systems is becoming increasingly complex. Identity management is important in the coordination of various systems, and public key infrastructure (PKI) is widely known as an identity management methods. In PKI, a certificate authority (CA) acts as a trust point to guarantee the identity of entities such as users, devices, and services. However, traditional CAs that delegate the operations to a specific organization are not always suitable for heterogeneous services, and a new methodology is required to enable multiple stakeholders to securely and cooperatively operate a CA. In this study, we introduce the concept of a consortium CA and propose a distributed public key certificate-issuing infrastructure that realizes a consortium CA. The proposed infrastructure enables multiple organizations to cooperatively operate a CA suitable for services involving multiple stakeholders. We identify four requirements for the cooperative operation of a consortium CA and design the proposed infrastructure with distributed ledger technology. Furthermore, we present the implementation of smart contracts with Hyperledger Fabric and prove that the proposed infrastructure satisfies the four requirements. Finally, we confirm that certificate issuance and verification are stable at approximately 4 and 3 ms, respectively.
The increased demand for data availability in every industry is driving individuals to exchange and store data on centralized platforms such as clouds so that the intended audience may access it. To facilitate data exchange and storage in the medical industry, organizations and patients are building cloud platforms. However, the most pressing issue that everyone faces is data protection and security. Here, we describe many techniques that are available to protect the system and meet the requirement for data privacy preservation in the medical industry. Some algorithms are Zero-Knowledge Proof, Principal Component Analysis and Random Projection, Generative Adversarial Networks, blockchain and cloud computing, Quasi-Identifier Recognition, Q-learning Neural Network, digital signature, and others.
Matteo Loporchio, Anna Bernasconi, Damiano Di Francesco Maesa, Laura Ricci
Set accumulators are cryptographic primitives used to represent arbitrarily large sets of elements with a single constant-size value and to efficiently verify whether a value belongs to that set. Accumulators support the generation of membership proofs, meaning that they can certify the presence of a given value among the elements of a set. In this paper we present an overview of the theoretical concepts underlying set accumulators, we compare the most popular constructions from a complexity perspective, and we survey a number of their applications related to blockchain technology. In particular, we focus on four different use cases: query authentication, stateless transactions validation, anonymity enhancement, and identity management. For each of these scenarios, we examine the main problems they introduce and discuss the most relevant accumulator-based solutions proposed in the literature. Finally, we point out the common approaches between the proposals and highlight the currently open problems in each field.
Ring signcryption with no group administrator satisfies the decentralization and blockchain anonymity. In this article, we construct new lattice-based ring signcryption scheme suitable for consortium blockchain (CB-LRSCS), in which the smart contract controls the process of signcryption and unsigncryption to make the system be fair and reliable. CB-LRSCS can protect the user privacy by reducing the connection between blockchain and user information, and it satisfies the reliability in ethereum environment. CB-LRSCS also has the characteristics of high efficiency, anti-quantum, anti-forgery, confidentiality and unconditional anonymity, and it can be applied in the electronic finance system.
With the massive amount of digital data generated everyday, transactions of digital goods become a trend. One of the essential requirements for such transactions is fairness, which is defined as that both of the seller and the buyer get what they want, or neither. Current fair trade protocols generally involve a trusted third-party (TTP), which achieves fairness by heavily relying on the TTP's behaviors and the two parties' trust in the TTP. With the emergence of Blockchain, its decentralization and transparency make it a very good candidate to replace the TTP. In this work, we attempt to design a secure and fair protocol for digital goods transactions through smart contracts on Blockchain. To ensure security of the digital goods, we propose an advanced passive proxy re-encryption (PRE) scheme, which enables smart contracts to transfer the decryption right to a buyer after receiving his/her payment. Furthermore, based on smart contracts and the proposed passive PRE scheme, a fair trade protocol for digital goods transactions is proposed, whose fairness is guaranteed by the arbitration protocol. The proposed protocol supports Ciphertext publicity and repeatable sale, while involving less number of interactions. Comprehensive experiment results validate the feasibility and effectiveness of the proposed protocol.
Handong Cui, Kwan Yin Chan, Tsz Hon Yuen, Xin Kang · 5 authors
Abstract In most threshold Elliptic Curve Digital Signature Algorithm (ECDSA) signatures using additively homomorphic encryption, the zero-knowledge (ZK) proofs related to the ciphertext or the message space are the bottleneck in terms of bandwidth as well as computation time. In this paper, we propose a compact ZK proof for relations related to the Castagnos–Laguillaumie (CL) encryption, which is 33% shorter and 29% faster than the existing work in PKC 2021. We also give new ZK proofs for relations related to homomorphic operations over the CL ciphertext. These new ZK proofs are useful to construct a bandwidth-efficient universal composable-secure threshold ECDSA without compromising the proactive security and the non-interactivity. In particular, we lowered the communication and computation cost of the key refresh algorithm in the Paillier-based counterpart from $O(n^3)$ to $O(n^2)$. Considering a 5-signer setting, the bandwidth is better than the Paillier-based counterpart for up to 99, 95 and 35% for key generation, key refreshment and pre-signing, respectively.
Federated learning is a decentralized machine learning paradigm that allows multiple clients to collaborate by leveraging local computational power and the model’s transmission. This method reduces the costs and privacy concerns associated with centralized machine learning methods while ensuring data privacy by distributing training data across heterogeneous devices. On the other hand, federated learning has the drawback of data leakage due to the lack of privacy-preserving mechanisms employed during storage, transfer, and sharing, thus posing significant risks to data owners and suppliers. Blockchain technology has emerged as a promising technology for offering secure data-sharing platforms in federated learning, especially in Industrial Internet of Things (IIoT) settings. This survey aims to compare the performance and security of various data privacy mechanisms adopted in blockchain-based federated learning architectures. We conduct a systematic review of existing literature on secure data-sharing platforms for federated learning provided by blockchain technology, providing an in-depth overview of blockchain-based federated learning, its essential components, and discussing its principles, and potential applications. The primary contribution of this survey paper is to identify critical research questions and propose potential directions for future research in blockchain-based federated learning.
Javier José Díaz Rivera, Waleed Akbar, Talha Ahmed Khan, Muhammad Afaq · 5 authors
Zero Trust Networking (ZTN) is a security model where no default trust is given to entities in a network infrastructure. The first bastion of security for achieving ZTN is strong identity verification. Several standard methods for assuring a robust identity exist (E.g., OAuth2.0, OpenID Connect). These standards employ JSON Web Tokens (JWT) during the authentication process. However, the use of JWT for One Time Token (OTT) enrollment has a latent security issue. A third party can intercept a JWT, and the payload information can be exposed, revealing the details of the enrollment server. Furthermore, an intercepted JWT could be used for enrollment by an impersonator as long as the JWT remains active. Our proposed mechanism aims to secure the ownership of the OTT by including the JWT as encrypted metadata into a Non-Fungible Token (NFT). The mechanism uses the blockchain Public Key of the intended owner for encrypting the JWT. The blockchain assures the JWT ownership by mapping it to the intended owner's blockchain public address. Our proposed mechanism is applied to an emerging Zero Trust framework (OpenZiti) alongside a permissioned Ethereum blockchain using Hyperledger Besu. The Zero Trust Framework provides enrollment functionality. At the same time, our proposed mechanism based on blockchain and NFT assures the secure distribution of OTTs that is used for the enrollment of identities.
Over the years, Cloud Computing has become rapidly embraced due to its flexibility and cost-effectiveness. However, it also presents a number of security challenges, especially with regards to access control. Conventional access control methods, like Role-based Access Control, have limitations in terms of centralized control, lack of transparency, and susceptibility to cyber-attacks. As a result, there is a need for more efficient, transparent, and secure Access Control mechanisms in Cloud Computing environments. In this Research paper, we put forward a non-centralized and tamper-proof Access Control mechanism that uses smart contract blockchain technology to address these limitations. Our model leverages the Ethereum platform's smart contract feature to stockpile access control programs and enable secure verification of user’s access requests. The smart contract blockchain is immutable, transparent, and decentralized, which makes it resistant to tampering and provides a high degree of transparency in the access control process. Our proposed model has several advantages over traditional access control mechanisms. Firstly, it provides an effective and automated approach to manage access control policies. With our model, access control policies can be easily updated and enforced through smart contracts, which eliminates the need for manual updates and reduces the risk of errors. Secondly, it provides a high degree of transparency in the access control process, which allows users to verify the legitimacy of their access requests and ensures that access control policies are being enforced fairly. Finally, it offers a heightened level of security, as the Smart Contract Blockchain is resistant to tampering and it offers a platform for Access Control that is both secure and non-centralized. To assess the efficacy of our model for Access Control management, we performed a series of experiments in a simulated Cloud Computing environment. The findings revealed that our model offers a superior and secure approach for managing access control programs compared to conventional methods. To conclude, our study suggests a secure and non-centralized access control solution by utilizing blockchain technology through smart contracts, to address the limitations of conventional Access Control methods in Cloud Computing environments. Our model provides a more efficient, transparent, and secure way to manage Access Control program to maintain the authenticity and confidentiality of Cloud services.
Blockchain has been recognised as a technological breakthrough with the ability to support new decentralised security-based solutions in sectors such as information technology and finance. Blockchain allows different communities to create Decentralised Autonomous Organisations (DAOs), which are self-organised democratic organisations controlled by smart contracts. This paper presents a new DAO model for the procurement of services by public organisations, such as government agencies. To demonstrate the advantages of this solution, this work looks specifically at current public procurement systems that resort to third-party contractors that manage these negotiations. Third parties lack the transparency, security, and democratic representation that a DAO can provide. We present the implementation of a DAO as a set of smart contracts executed on Ethereum-compatible permissionless blockchains, supported by a consensus algorithm, replacing third-party contractors.
A generalized scheme of remote electronic voice based on homomorphic encryption is considered. Two methods of protecting the voting system from the threat from the voter, consisting in incorrect filling of the ballot by the voter, are investigated. Both methods are based on the algorithms of “zero-knowledge proof”. Evaluations of the complexity of calculations in the formation of proof of the correctness of filling in the ballot by the voter and Evaluations of the complexity of verification of the proof by the controlling party are obtained. A comparative analysis of the complexity of the implementation of both methods has shown that the method based on the proof based on the equality of logarithms has less complexity of calculations on the voter's side compared to the method based on the mixing of votes. At the same time, the second method (the method of mixing votes) requires 1.67 times less calculations in the blockchain, which becomes a significant factor in choosing the second method in favor of a large number of voters.
Open access
Internet Traffic Analysis and Secure E-voting
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
Joonyoung Lee, Myeonghyun Kim, Kisung Park, Sungkee Noh · 7 authors
Recently, with the increasing application of the Internet of Things (IoT), various IoT environments such as smart factories, smart homes, and smart grids are being generated. In the IoT environment, a lot of data are generated in real time, and the generated IoT data can be used as source data for various services such as artificial intelligence, remote medical care, and finance, and can also be used for purposes such as electricity bill generation. Therefore, data access control is required to grant access rights to various data users in the IoT environment who need such IoT data. In addition, IoT data contain sensitive information such as personal information, so privacy protection is also essential. Ciphertext-policy attribute-based encryption (CP-ABE) technology has been utilized to address these requirements. Furthermore, system structures applying blockchains with CP-ABE are being studied to prevent bottlenecks and single failures of cloud servers, as well as to support data auditing. However, these systems do not stipulate authentication and key agreement to ensure the security of the data transmission process and data outsourcing. Accordingly, we propose a data access control and key agreement scheme using CP-ABE to ensure data security in a blockchain-based system. In addition, we propose a system that can provide data nonrepudiation, data accountability, and data verification functions by utilizing blockchains. Both formal and informal security verifications are performed to demonstrate the security of the proposed system. We also compare the security, functional aspects, and computational and communication costs of previous systems. Furthermore, we perform cryptographic calculations to analyze the system in practical terms. As a result, our proposed protocol is safer against attacks such as guessing attacks and tracing attacks than other protocols, and can provide mutual authentication and key agreement functions. In addition, the proposed protocol is more efficient than other protocols, so it can be applied to practical IoT environments.
Blockchain technology has gained significant attention as a solution for ensuring data integrity, confidentiality, and availability in a trustless environment.Its main objective is to safeguard data from both internal and external cyberattacks by leveraging the collective power of the network to counter malicious attempts.In this project, we aim to develop a decentralized messaging application using XMTP (replace with the correct protocol if applicable).Our application will enable secure and anonymous transmission of encrypted messages.The Ethereum platform will be utilized for deploying our blockchain network.By utilizing a distributed architecture and a flexible communication protocol, our application will be resilient against various forms of suppression.XMTP's extensible design allows for a wide range of use cases in exchanging message data between web3 identities.Additionally, the XMTP network ensures message persistence and associates them with web3 identities rather than specific client apps.As a result, each web3 identity possesses a portable inbox accessible through any XMTP-enabled client application.
The main characteristics of blockchains, such as security and traceability, have enabled their use in many distinct scenarios, such as the rise of new cryptocurrencies and decentralized applications (dApps). However, part of the information exchanged with the typical blockchains is public, which can lead to privacy issues. To avoid or mitigate these issues, some blockchains are applying mechanisms to deal with data privacy. Trusted Execution Environments, the basis of confidential computing, and secure Multi-party Computation are two technologies that can be applied in that sense. In this paper, we analyzed seven blockchain technologies that apply mechanisms to improve data privacy. We defined seven technical questions related to common requirements for decentralized applications and, to answer each question, we reviewed the available documentation and gathered information from chat channels. We briefly present each blockchain technology and the answers to each technical question. Finally, we present a table summarizing the information and showing which technologies are more prominent.