Threshold signatures are a fundamental cryptographic primitive used in many practical applications. As proposed by Boneh and Komlo (CRYPTO'22), TAPS is a threshold signature that is a hybrid of privacy and accountability. It enables a combiner to combine t signature shares while revealing nothing about the threshold t or signing quorum to the public and asks a tracer to track a signature to the quorum that generates it. However, TAPS has three disadvantages: it 1) structures upon a centralized model, 2) assumes that both combiner and tracer are honest, and 3) leaves the tracing unnotarized and static. In this work, we introduce Decentralized, Threshold, dynamically Accountable and Private Signature (DeTAPS) that provides decentralized combining and tracing, enhanced privacy against untrusted combiners (tracers), and notarized and dynamic tracing. Specifically, we adopt Dynamic Threshold Public-Key Encryption (DTPKE) to dynamically notarize the tracing process, design non-interactive zero knowledge proofs to achieve public verifiability of notaries, and utilize the Key-Aggregate Searchable Encryption to bridge TAPS and DTPKE so as to awaken the notaries securely and efficiently. In addition, we formalize the definitions and security requirements for DeTAPS. Then we present a generic construction and formally prove its security and privacy. To evaluate the performance, we build a prototype based on SGX2 and Ethereum.
Junrui Liu, Ian Kretz, Hanzhi Liu, Bryan E‐Xin Tan · 10 authors
Zero-knowledge (ZK) proof systems have emerged as a promising solution for building security-sensitive applications. However, bugs in ZK applications are extremely difficult to detect and can allow a malicious party to silently exploit the system without leaving any observable trace. This paper presents Coda, a novel statically-typed language for building zero-knowledge applications. Critically, Coda makes it possible to formally specify and statically check properties of a ZK application through a rich refinement type system. One of the key challenges in formally verifying ZK applications is that they require reasoning about polynomial equations over large prime fields that go beyond the capabilities of automated theorem provers. Coda mitigates this challenge by generating a set of Coq lemmas that can be proven in an interactive manner with the help of a tactic library. We have used Coda to re-implement 77 arithmetic circuits from widely-used Circom libraries and applications. Our evaluation shows that Coda makes it possible to specify important and formally verify correctness properties of these circuits. Our evaluation also revealed 6 previously-unknown vulnerabilities in the original Circom projects.
As part of vehicle to everything (V2X) environments, intelligent connected vehicles (ICVs) generate a large amount of data, which can be exploited securely and effectively through decentralized techniques such as federated learning (FL). Existing FL systems, however, are vulnerable to attacks and barely meet the security requirements for real-world applications. If malicious or compromised ICVs upload inaccurate or low-quality local model updates to the central aggregator, they may reduce the accuracy of the global model, thereby reducing drivers safety and efficiency. This paper aims to alleviate these concerns by presenting BV-ICVs, a blockchain-enabled and privacy-preserving FL framework for ICVs in an edge-envisioned V2X environment. This system uses Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zkSNARKs) verification that is compiled as smart contracts to prevent malicious, compromised or even rational ICVs from uploading unreliable, erroneous or low-quality model updates. The verification process is embedded within the consensus of the underlying permissioned blockchain, which maximizes both the efficiency of the process and the utilization of computer resources. As demonstrated by discussions, security analysis, and numerical results, BV-ICVs reduced data poisoning attacks and increased the privacy protection and accuracy of FL.
Since the concern of privacy leakage extremely discourages user participation in sharing data, federated learning has gradually become a promising technique for both academia and industry for achieving collaborative learning without leaking information about the local data. Unfortunately, most federated learning solutions cannot efficiently verify the execution of each participant's local machine learning model and protect the privacy of user data, simultaneously. In this article, we first propose a Zero-Knowledge Proof-based Federated Learning (ZKP-FL) scheme on blockchain. It leverages zero-knowledge proof for both the computation of local data and the aggregation of local model parameters, aiming to verify the computation process without requiring the plaintext of the local data. We further propose a Practical ZKP-FL (PZKP-FL) scheme to support fraction and non-linear operations. Specifically, we explore a Fraction-Integer mapping function, and use Taylor expansion to efficiently handle non-linear operations while maintaining the accuracy of the federated learning model. We also analyze the security of PZKP-FL. Performance analysis demonstrates that the whole running time of the PZKP-FL scheme is approximately less than one minute in parallel execution.
Abstract With the rapid advancements of the mineral industry, the data generated by this industry chain have increased dramatically. To reduce the growing pressure of data storage and security risks, we design a credible on-chain and off-chain collaborative dual storage system that integrates blockchain technology and Interplanetary file system (IPFS), also construct a traceable and revocable multi-authority ciphertext-policy attributed-based encryption (CP-ABE) algorithm to meet the demand of privacy protection and dynamic fine-grained access control. Furthermore, the multi-authority layered authorization with a central authority model distributes system overhead while enabling the platform can be regulated. More importantly, our scheme achieves accurate trace of the malicious users by white-box traceability and capable of implementing indirect immediate user and attribute revocation without requiring key or ciphertext updates. Finally, the proposed scheme is indistinguishably secure under chosen-plaintext attack (IND-CPA) in the standard model. And the performance analysis demonstrates that our scheme is feature-rich, practical and efficient.
Ricardo Martins Gonçalves, Miguel Mira da Silva, Paulo Rupino da Cunha
The immutability of data stored in a blockchain is a crucial pillar of trust in this technology, which has led to its increasing adoption in various use cases. However, there are situations where the inability to change or delete data may be illegal. European Union’s General Data Protection Regulation (GDPR)—applying to any company processing personal data from European citizens—explicitly entitles individuals to the right to rectification and the right to be forgotten. In this paper, we describe the design of a system to deploy and process survey data in a GDPR-compliant manner. It combines an Hyperledger Fabric blockchain to ensure that data cannot be tampered with and InterPlanetary File Systems (IPFS) for storage. With the proposed arrangement, we reap several security benefits enabled by blockchain’s immutability without running afoul of the regulations. Furthermore, the proof-of-concept is generic and can easily be adapted to various domains.
Ring Confidential Transactions (RingCT) is a protocol associated with the privacy-focused cryptocurrency Monero and is used to hide the transaction amount from the third party while still providing the confidentiality of the hide transaction. With the Pederson commitment scheme, ring signature, and other cryptographic constructions, RingCT plays a major role in making the transactions of Monero private. As a privacy coin, Monero has the unique property of fungibility in the cryptocurrency market from the protocols implemented. These protocols provided opportunities and challenges for its future. In this paper, the version of the protocol implemented in Monero is first inspected, including the commitment to zero and the range proof. Then, two critical cryptographic constructions used by RingCT 2.0, the accumulator and the signature of knowledge, are introduced. Finally, the influence of RingCT and other privacy features and the current situation of privacy coin is discussed.
This paper explains the composition of the cryptocurrency wallet by analyzing a wallet’s components, functions, categories, the algorithm of signing, and security features as three major components used in the constitute of the cryptocurrency wallet, private key, public key, and address are introduced from their generation process with specific Elliptic Curve Digital Signature Algorithm secp256k1 and Keccak hash function. A variety of crypto wallets are divided into different categories by their purpose of use, the form of display, and Internet connectivity, and multiple crypto wallets are explained in the second part of this paper. The elliptic curve secp256k1 is selected in Ethereum for both calculating the public key information and performing signing transactions. This paper details secp256k1 and Keystore used behind the signing process and security of cryptocurrency wallet and outlines potential risks due to the development of computing power and transfer of validation system in Ethereum.
Open access
Chaos-based Image/Signal Encryption
Advanced Steganography and Watermarking Techniques
Ethereum digital signatures have been found to make progress, but there has yet to be a consensus regarding their significance and process. Using digital signatures in Ethereum ensures the security of users' money and the Safety of their transportation. Elliptic Curve Digital Signature Algorithm (ECDSA), private key, and public key play an important role here. This paper analyzes the details of Ethereum's Digital Signature based on existing information. First, it explained the general background information about Ethereum. Send explain the ERC-20. ERC-20 are digital assets that represent value. They could become more compatible with the new standard and allow other features. Then digital signatures are explained in detail. This part included ECDSA, private key, and public key. ECDSA is the most critical algorithm during the production process. Private and public keys are the key features to ensure Safety. The last part is the Keystore file system. Using the Keystore file system, users can secure their private keys for their cryptocurrency wallets. To access their account, the user must have a password generated by them. The unencrypted files, on the other hand, create a vulnerability in the key store, which is exposed by these unencrypted files. Once an attacker obtains the user's unencrypted key, he cannot only take control of the account but also sign transactions on behalf of the user.
Multi-party business processes rely on the collaboration of various players in a decentralized setting. Blockchain technology can facilitate the automation of these processes, even in cases where trust among participants is limited. Transactions are stored in a ledger, a replica of which is retained by every node of the blockchain network. The operations saved thereby are thus publicly accessible. While this enhances transparency, reliability, and persistence, it hinders the utilization of public blockchains for process automation as it violates typical confidentiality requirements in corporate settings. In this paper, we propose MARTSIA: A Multi-Authority Approach to Transaction Systems for Interoperating Applications. MARTSIA enables precise control over process data at the level of message parts. Based on Multi-Authority Attribute-Based Encryption (MA-ABE), MARTSIA realizes a number of desirable properties, including confidentiality, transparency, and auditability. We implemented our approach in proof-of-concept prototypes, with which we conduct a case study in the area of supply chain management. Also, we show the integration of MARTSIA with a state-of-the-art blockchain-based process execution engine to secure the data flow.
Abstract A Service Level Agreement (SLA) establishes the trustworthiness of service providers and consumers in several domains; including the Internet of Things (IoT). Given the proliferation of Blockchain technology, we find it compelling to reconsider the assumption of trust and centralised governance typically practised in SLA management including monitoring, compliance assessment, and penalty enforcement. Therefore, we argue that, such critical tasks should be operated by blockchain-based smart contracts in a non-repudiable manner beyond the influence of any SLA party. This paper envisions an IoT scenario wherein a firefighting station outsources end-to-end IoT operations to a specialised service provider. The contractual relationship between them is governed by an SLA which stipulates a set of quality requirements and violation consequences. The main contribution of this paper lies in designing, deploying and empirically experimenting a novel blockchain-based SLA monitoring and compliance assessment framework in the context of IoT. This is done by utilising Hyperledger Fabric (HLF), an enterprise-grade blockchain technology. Our work highlights a set of considerations and best practice at two sides, the IoT application monitoring-side and the blockchain-side. Moreover, it experimentally validates the reliability of the proposed monitoring approach, which collects relevant metrics from each IoT component and examines them against the quality requirements stated in the SLA. Finally, we propose a novel design for smart contracts at the blockchain-side, analyse and benchmark the performance, and demonstrate that the new design proves to successfully handle Multiversion Concurrency Control (MVCC) conflicts typically encountered in blockchain applications, while maintaining sound throughput and latency.
Frédéric Hayek, Mirko Koscina, Pascal Lafourcade, Charles Olivier-Anclin
Private permissioned blockchains are becoming gradually more sought-after. Such systems are reachable by authorized users, and tend to be completely transparent to whoever interacts with the blockchain. In this paper, we mitigate the latter. Authorized users can now stay unlinked to the transaction they propose in the blockchain while being authenticated before being allowed to interact. As a first contribution, we developed a consensus algorithm for private permissioned blockchains based on Hyperledger Fabric and the Practical Byzantine Fault Tolerance consensus. Building on this blockchain, five additional variations achieving various client-wise privacy preserving levels are proposed. These different protocols allow for different use cases and levels of privacy control and sometimes its revocation by an authority. All our protocols guarantee the unlinkability of transactions to their issuers achieving anonymity or pseudonymity. Miners can also inherit some of the above privacy preserving setting. Naturally, we maintain liveness and safety of the system and its data.
Summary Outsourcing storage and computation to cloud servers have become a trend. Although searchable symmetric encryption (SSE) had handled the data privacy issue caused by honest‐but‐curious servers, a semi‐honest server may return incomplete or incorrect results when users search for their encrypted data. To against such servers, scholars have recently used blockchain/Ethereum‐based SSE schemes which utilize the public, that is, active nodes, to verify the search process. However, the search operation in existing schemes is very expansive in terms of fee and time. In this paper, we propose a new blockchain‐based searchable encryption framework with search optimized, that is, free of charge, quicker, and more private, at the cost of some extra storage. Besides, we design a general and efficient verification algorithm for our framework, which makes the search verifiable. In addition, we deploy an instance of our framework on an official Ethereum test network, and the experimental results and evaluations demonstrate the advantage of our framework.
Distributed Ledger Technology (DLTs) or blockchains have been steadily emerging and providing innovation in the past decade for several use cases, ranging from financial networks, to notarization, or trustworthy execution via smart contracts. DLTs are enticing due to their properties of decentralization, non-repudiation, and auditability (transparency). These properties are of high potential to access control systems that can be implemented on-chain, and are executed without infringement and full transparency.
Smart contracts are programs that are executed on the blockchain and can hold, manage and transfer assets in the form of cryptocurrencies. The contract's execution is then performed on-chain and is subject to consensus, i.e. every node on the blockchain network has to run the function calls and keep track of their side-effects including updates to the balances and contract's storage. The notion of gas is introduced in most programmable blockchains, which prevents DoS attacks from malicious parties who might try to slow down the network by performing time-consuming and resource-heavy computations. While the gas idea has largely succeeded in its goal of avoiding DoS attacks, the resulting fees are extremely high. For example, in June-September 2022, on Ethereum alone, there has been an average total gas usage of 2,706.8 ETH ≈ 3,938,749 USD per day. We propose a protocol for alleviating these costs by moving most of the computation off-chain while preserving enough data on-chain to guarantee an implicit consensus about the contract state and ownership of funds in case of dishonest parties. We perform extensive experiments over 3,330 real-world Solidity contracts that were involved in 327,132 transactions in June-September 2022 on Ethereum and show that our approach reduces their gas usage by 40.09 percent, which amounts to a whopping 442,651 USD.
Open access
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
Data access control is a crucial aspect of data management. Actors who want to share data need systems to manage consent in order to decide who can access their data. This guarantees the privacy of data, which is often sensitive. As a secure distributed ledger, the blockchain is widely used today to manage consent for data access. However, a blockchain is not ideal for storing large volumes of data due to its characteristics. Therefore, it is often coupled with off-chain systems to facilitate the storage of these kinds of data. Therefore, data located outside the blockchain require security procedures. This article proposes a securing mechanism based on data encryption to secure data in off-chain storage in blockchain-based consent systems. The protocol uses a symmetric key system, which prevents the reading of data stored outside the sphere of the blockchain by malicious actors who would have access. The mechanism’s set up allows each set of data to be encrypted with a symmetric key that is anchored in a blockchain. This key is then used by the actors who have obtained the consent of the data owner to access and read the data stored outside the blockchain.
The access control (AC) system in an IoT (Internet of Things) context ensures that only authorized entities have access to specific devices and that the authorization procedure is based on pre-established rules. Recently, blockchain-based AC systems have gained attention within research as a potential solution to the single point of failure issue that centralized architectures may bring. Moreover, zero-knowledge proof (ZKP) technology is included in blockchain-based AC systems to address the issue of sensitive data leaking. However, current solutions have two problems: (1) systems built by these works are not adaptive to high-traffic IoT environments because of low transactions per second (TPS) and high latency; (2) these works cannot fully guarantee that all user behaviors are honest. In this work, we propose a blockchain-based AC system with zero-knowledge rollups to address the aforementioned issues. Our proposed system implements zero-knowledge rollups (ZK-rollups) of access control, where different AC authorization requests can be grouped into the same batch to generate a uniform ZKP, which is designed specifically to guarantee that participants can be trusted. In low-traffic environments, sufficient experiments show that the proposed system has the least AC authorization time cost compared to existing works. In high-traffic environments, we further prove that based on the ZK-rollups optimization, the proposed system can reduce the authorization time overhead by 86%. Furthermore, the security analysis is presented to show the system's ability to prevent malicious behaviors.
Zibin Zheng, Neng Zhang, Jianzhong Su, Zhijie Zhong · 6 authors
Smart contracts are programs deployed on a blockchain and are immutable once deployed. Reentrancy, one of the most important vulnerabilities in smart contracts, has caused millions of dollars in financial loss. Many reentrancy detection approaches have been proposed. It is necessary to investigate the performance of these approaches to provide useful guidelines for their application. In this work, we conduct a large-scale empirical study on the capability of five well-known or recent reentrancy detection tools such as Mythril and Sailfish. We collect 230,548 verified smart contracts from Etherscan and use detection tools to analyze 139,424 contracts after deduplication, which results in 21,212 contracts with reentrancy issues. Then, we manually examine the defective functions located by the tools in the contracts. From the examination results, we obtain 34 true positive contracts with reentrancy and 21,178 false positive contracts without reentrancy. We also analyze the causes of the true and false positives. Finally, we evaluate the tools based on the two kinds of contracts. The results show that more than 99.8% of the reentrant contracts detected by the tools are false positives with eight types of causes, and the tools can only detect the reentrancy issues caused by call.value(), 58.8% of which can be revealed by the Ethereum's official IDE, Remix. Furthermore, we collect real-world reentrancy attacks reported in the past two years and find that the tools fail to find any issues in the corresponding contracts. Based on the findings, existing works on reentrancy detection appear to have very limited capability, and researchers should turn the rudder to discover and detect new reentrancy patterns except those related to call.value().
With the advent of the era of big data, privacy computing analyzes and calculates data on the premise of protecting data privacy, to achieve data 'available and invisible'. As an important branch of secure multi-party computation, the geometric problem can solve practical problems in the military, national defense, finance, life, and other fields, and has important research significance. In this paper, we study the similarity problem of geometric graphics. First, this paper proposes the adjacency matrix vector coding method of isomorphic graphics, and use the Paillier variant encryption cryptography to solve the problem of isomorphic graphics confidentiality under the semi-honest model. Using cryptography tools such as elliptic curve cryptosystem, zero-knowledge proof, and cut-choose method, this paper designs a graphic similarity security decision protocol that can resist malicious adversary attacks. The analysis shows that the protocol has high computational efficiency and has wide application value in terrain matching, mechanical parts, biomolecules, face recognition, and other fields.
Open access
Biometric Identification and Security
Advanced Steganography and Watermarking Techniques
Cryptocurrencies offer various benefits in terms of privacy protection and cross-border transactions, but they have also been used for illicit activities such as money laundering due to their anonymous nature and the difficulty of cross-border regulation. Additionally, the unethical actions of some virtual asset service providers (VASPs), such as rug pulls and the embezzlement of user funds, have further eroded the trust between users and VASPs. Implementing identity management on blockchains can help restore trust between users and VASPs. However, current solutions have privacy concerns as identity providers have access to the asset balances and transaction records of each user’s wallet account, and no solution can support all public blockchains unconditionally. To address these issues, this paper proposes a multi-chain aggregated identity scheme. In this scheme, the identity provider will issue a non-fungible token (NFT) for users who have undergone verification, and wallet accounts from different blockchains will be added to a cryptographic accumulator. The accumulator value is then bound to the identity NFT through a smart contract by the user. This allows the user to prove to others that the identity of the wallet account owner has been verified. The use of accumulators also allows users to combine proof for multiple wallets into a single proof, which significantly improves the efficiency and provides a way for VASPs such as centralized exchanges to demonstrate Proof of Reserves (PoR) to users. Importantly, this scheme preserves privacy as neither the identity provider nor the VASPs can link the user’s real identity with the wallet accounts. Only regulators can access the user’s identity data held by the identity provider and the user’s wallet account held by the VASP to link real identities with wallet accounts for the purpose of sanctions or criminal investigations. Additionally, the scheme supports all blockchains by allowing wallet accounts from any public blockchain to be added to the accumulator. Furthermore, the NFT implementation in the scheme helps prevent identity loss or theft, as it can only be transferred by the identity provider.
Open access
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
For Nakamoto's longest-chain consensus protocol, whose proof-of-work (PoW) and proof-of-stake (PoS) variants power major blockchains such as Bitcoin and Cardano, we revisit the classic problem of the security--performance tradeoff: Given a network of nodes with finite communication- and computation-resources, against what fraction of adversary power is Nakamoto consensus (NC) secure for a given block production rate? State-of-the-art analyses of NC fail to answer this question, because their bounded-delay model does not capture the rate limits to nodes' processing of blocks, which cause congestion when blocks are released in quick succession. We develop a new analysis technique to prove a refined security--performance tradeoff for PoW NC in a bounded-capacity model. In this model, we show that, in contrast to the classic bounded-delay model, Nakamoto's private attack is no longer the worst attack, and a new attack we call the teasing strategy, that exploits congestion, is strictly worse. In PoS, equivocating blocks can exacerbate congestion, making traditional PoS NC insecure except at very low block production rates. To counter such equivocation spamming, we present a variant of PoS NC we call Blanking NC (BlaNC), which achieves the same resilience as PoW NC.
The mobile healthcare (mHealth) is a promising and fascinating paradigm, which can dramatically improve the quality of healthcare delivery by providing remote diagnosis and medical record sharing. Now, the mHealth faces serious challenges such as data leakage and unauthorised access currently. Attribute-based encryption (ABE) which has been employed for mHealth is an excellent cryptographic primitive of securing data sharing. However, there are still some security and efficiency issues in the ABE-based data sharing scheme for mHealth. Firstly, the explicit storage of access policy may expose the privacy of users. Secondly, the computation cost is high, especially in the mHealth with IoT devices. Thirdly, the authentication of access rights to shared data is usually performed by the centralised third parties or IoT devices with limited resources. To handle the above issues, this paper presents a privacy-preserving and efficient data sharing scheme. The scheme partially hides access policy to protect user's privacy, and introduces an offline mechanism in key generation and encryption phase to improve efficiency of mHealth. Furthermore, it also provides decentralised and trusted authentication of data access right based on blockchain. The security proofs and the experiment results demonstrate that the presented scheme has better security and efficiency.
Lewis Golightly, Paolo Modesti, Rémi Garcia, Victor Chang
Access Control is a crucial defense mechanism organizations can deploy to meet modern cybersecurity needs and legal compliance with data privacy. The aim is to prevent unauthorized users and systems from accessing protected resources in a way that exceeds their permissions. The present survey aims to summarize state-of-the-art Access Control techniques, presenting recent research trends in this area. Moreover, as the cyber-attack landscape and zero-trust networking challenges require organizations to consider their Information Security management strategies carefully, in this study, we present a review of contemporary Access Control techniques and technologies being discussed in the literature and the various innovations and evolution of the technology. We also discuss adopting and applying different Access Control techniques and technologies in four upcoming and crucial domains: Cloud Computing, Blockchain, the Internet of Things, and Software-Defined Networking. Finally, we discuss the business adoption strategies for Access Control and how the technology can be integrated into a cybersecurity and network architecture strategy.