Mohd Wasim, Charchit Kumar Chauhan, Abhay Pratap Singh, Arushi Gupta
Blockchain technology has the potential to revolutionize the way we conduct transactions by offering a secure, decentralized, and transparent system. In this paper, we present a comprehensive overview of a blockchain-based transaction system, highlighting its key features and advantages. We discuss the underlying cryptographic mechanisms and consensus algorithms that ensure the security and integrity of transactions, as well as the various privacy-enhancing features, such as pseudonymity and zero-knowledge proofs. The paper also explores the challenges and limitations of blockchain-based transaction systems and identifies areas for future improvement. This study provides a thorough analysis of the current state of blockchain technology and its potential for transforming the way we conduct transactions, making it an essential resource for researchers, practitioners, and anyone interested in the future of finance and technology.
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
Philipp G. Haselwarter, Exequiel Rivas, Antoine Van Muylder, Théo Winterhalter · 9 authors
State-separating proofs (SSP) is a recent methodology for structuring game-based cryptographic proofs in a modular way, by using algebraic laws to exploit the modular structure of composed protocols. While promising, this methodology was previously not fully formalized and came with little tool support. We address this by introducing SSProve, the first general verification framework for machine-checked state-separating proofs. SSProve combines high-level modular proofs about composed protocols, as proposed in SSP, with a probabilistic relational program logic for formalizing the lower-level details, which together enable constructing machine-checked cryptographic proofs in the Coq proof assistant. Moreover, SSProve is itself fully formalized in Coq, including the algebraic laws of SSP, the soundness of the program logic, and the connection between these two verification styles. To illustrate SSProve, we use it to mechanize the simple security proofs of ElGamal and pseudo-random-function–based encryption. We also validate the SSProve approach by conducting two more substantial case studies: First, we mechanize an SSP security proof of the key encapsulation mechanism–data encryption mechanism (KEM-DEM) public key encryption scheme, which led to the discovery of an error in the original paper proof that has since been fixed. Second, we use SSProve to formally prove security of the sigma-protocol zero-knowledge construction, and we moreover construct a commitment scheme from a sigma-protocol to compare with a similar development in CryptHOL. We instantiate the security proof for sigma-protocols to give concrete security bounds for Schnorr’s sigma-protocol.
Pedagogical ergonomics deals with the issues of rationalization of teacher's work and students' learning. The subject of pedagogical ergonomics is "human - educational environment". In recent years the educational environment has changed significantly under the influence of the process of its digitalization. It changes the psychology of teachers and students, gives rise to a number of safety issues and new aspects in the ergonomics of the educational process - its efficiency, rationality, safety, which remain little-studied. This article examines the use of artificial intelligence, zero-knowledge proof technology and machine learning in education from the perspective of basic principles of ergonomics - performance, efficiency, comfort of educational work, its safety. The article shows that digitalization of the educational environment helps to solve a number of problems of pedagogical ergonomics and serves to improve the quality of education and its accessibility for all. At the same time, the problems of using artificial intelligence in education are also noted. The possibilities of zero-knowledge proof technology that can help to reduce the risks of digitalization of the educational environment are considered.
Ismail Afia, Hisham S. Galal, Riham AlTawy, Amr Youssef
In second-hand vehicle markets, blockchains are being proposed as means to provide verification of vehicle history, a.k.a. vehicle passport (VP). However, given that confidentiality of VPs often contradicts public verification, blockchains are not used to their full potential in the proposed frameworks. Specifically, although blockchain smart contracts offer a decentralized mechanism for untrusted parties to fairly exchange digital assets without the need for a trusted third party, VP exchange is always carried off-chain. In this work, we investigate the problem of “fair exchange” of confidential VPs over public blockchains where its plain information must be verified against its publicly committed value. We propose a zero-knowledge proof, called Consistent Commitment Encryption (CCE), that enables the public verification of the consistency between ElGamal encryption of a given VP and its Pedersen commitment. We employ our CCE to build vPass, a decentralized vehicle passport framework that enables second-hand vehicle buyers to purchase vehicle history information from designated service providers and get it verified and delivered on-chain while preserving its confidentiality. The security of CCE relies on the intractability of the discrete logarithm problem in elliptic curve groups and it has no trusted setup. We formally prove that CCE is sound, complete, and witness indistinguishable proof of knowledge, and report on comparisons with other generic proof systems. Moreover, we show that vPass provides fair exchange and confidentiality of the vehicle history, and compare it to existing VP systems. Finally, we provide a proof of concept implementation on Ethereum and report the system performance metrics.
Even as the blockchain bubble bursts, the legacy of decades of work in cryptography is now beginning to ripple through into commercial reality. And the blockchain's ecosystem may prove to be fertile ground for many of these techniques to be tried to see how well they can work at scale. However, continuing problems of computational overhead may mean both zero-knowledge proofs, homomorphic encryption and their derivatives wind up being squeezed into niches where only they can satisfy a need. Elsewhere, the market may well continue to make do with what it can using classic public-key encryption and computing devices.
Roi Bar-Zur, Ameer Abu-Hanna, Ittay Eyal, Aviv Tamar
The security of proof-of-work blockchain protocols critically relies on incentives. Their operators, called miners, receive rewards for creating blocks containing user-generated transactions. Each block rewards its creator with newly minted tokens and with transaction fees paid by the users. The protocol stability is violated if any of the miners surpasses a threshold ratio of the computational power; she is then motivated to deviate with selfish mining and increase her rewards.Previous analyses of selfish mining strategies assumed constant rewards. But with statistics from operational systems, we show that there are occasional whales – blocks with exceptional rewards. Modeling this behavior implies a state-space that grows exponentially with the parameters, becoming prohibitively large for existing analysis tools.We present the WeRLman1framework to analyze such models. WeRLman uses deep Reinforcement Learning (RL), inspired by the state-of-the-art AlphaGo Zero algorithm. Directly extending AlphaGo Zero to a stochastic model leads to high sampling noise, which is detrimental to the learning process. Therefore, WeRLman employs novel variance reduction techniques by exploiting the recurrent nature of the system and prior knowledge of transition probabilities. Evaluating WeRLman against models we can accurately solve demonstrates it achieves unprecedented accuracy in deep RL for blockchain.We use WeRLman to analyze the incentives of a rational miner in various settings and upper-bound the security threshold of Bitcoin-like blockchains. We show, for the first time, a negative relationship between fee variability and the security threshold. The previously known bound, with constant rewards, stands at 0.25 [2]. We show that considering whale transactions reduces this threshold considerably. In particular, with Bitcoin historical fees and its future minting policy, its threshold for deviation will drop to 0.2 in 10 years, 0.17 in 20 years, and to 0.12 in 30 years. With recent fees from the Ethereum smart-contract platform, the threshold drops to 0.17. These are below the common sizes of large miners [3].
The operation of computing$n$scalar multiplications in an elliptic curve group and then adding them together is called n-scalar multiplication.$n$-scalar multiplication is the essential operation for proof generation and verification in pairing-based trusted setup zero-knowledge succinct non-interactive argument of knowledge protocols, which enable the privacy-preserving features in blockchain applications. This paper proposed a method to compute$n$-scalar multiplication taking advantage of$3n$precomputed points. When instantiating over BLS12-381 curve, for$n=2^{c}\ (10\leq c\leq 22)$, which covers the majority of our purported applications, the proposed method showed 2.59% ∼ 12.26% theoretical speed improvement and demonstrated 1.63% ∼ 11.54% experimental improvement against Pippenger's bucket method.
Decentralizing crowdsourcing using blockchain removes the trusted mediator who may cause social biases in data aggregation and uncertainties in ensuring proper rewards to workers. Permissionless blockchain discloses all data on public ledgers, which compromises the privacy and anonymity of workers and induces free-riders. State-of-the-art anonymous crowdsourcing systems enable anonymity through identity registration of workers and a trusted setup for key generation. However, these systems fail to support anonymous payments to workers, which may compromise the identities of workers. In this paper, we incorporate anonymous payments in crowdsourcing and dispense with identity registration and trusted setup to support open anonymous participation from any worker. Our solution is based on the decentralized anonymous payment systems (e.g., Zerocoin), commitment schemes, and efficient non-interactive zero-knowledge proofs.
Sacha Servan-Schreiber, Simon Beyzerov, Eli Yablon, Hyojae Park
Function Secret Sharing (FSS; Eurocrypt 2015) allows a dealer to share a function f with two or more evaluators. Given secret shares of a function f, the evaluators can locally compute secret shares of f (x) for any input x, without learning information about f in the process.In this paper, we initiate the study of access control for FSS. Given the shares of f, the evaluators can ensure that the dealer is authorized to share the provided function. For a function family $\mathcal{F}$ and an access control list defined over the family, the evaluators receiving the shares of $f \in \mathcal{F}$ can efficiently check that the dealer knows the access key for f.This model enables new applications of FSS, such as: (1) anonymous authentication in a multi-party setting, (2) access control in private databases, and (3) authentication and spam prevention in anonymous communication systems.Our definitions and constructions abstract and improve the concrete efficiency of several recent systems that implement ad-hoc mechanisms for access control over FSS. The main building block behind our efficiency improvement is a discrete-logarithm zero-knowledge proof-of-knowledge over secret-shared elements, which may be of independent interest.We evaluate our constructions and show a 50–70× reduction in computational overhead compared to existing access control techniques used in anonymous communication. In other applications, such as private databases, the processing cost of introducing access control is only 1.5–3×, when amortized over databases with 500,000 or more items.
We proposed a new construction for contract wallets, smart contract applications that allow users to control their crypto assets. Users can manipulate their crypto assets by simply sending emails with no need to manage keys. These emails are verified using zero-knowledge proof (ZKP) along with their attached digital signatures that the sender domain server (SDS) generates according to DomainKeys Identified Mail. Unless the SDS forges the emails, the crypto assets remain secure in the proposed system. Moreover, the existing SDSs can be used as is by outsourcing additional work to a third party that is not necessarily trusted. The system supports various functions to manipulate crypto assets. We produced a tool for variable-regex mapping (VRM) that enables developers to build a new function without ZKP skills. For example, using the tool, we built a demo application where users can exchange crypto assets via Uniswap only with emails. The published version of this paper is available at https://doi.org/10.1109/ICBC56567.2023.10174932.
There has been intense interest over the last decade in implementations of probabilistic proofs (IPs, SNARKs, PCPs, and so on): protocols in which an untrusted party proves to a verifier that a given computation was executed properly, possibly in zero knowledge. Nevertheless, implementations still do not scale beyond small computations. A central source of overhead is the front-end: translating from the abstract computation to a set of equivalent arithmetic constraints. This paper introduces a general-purpose framework, called Distiller, in which a user translates to constraints not the original computation but an abstracted specification of it. Distiller is the first in this area to perform such transformations in a way that is provably safe. Furthermore, by taking the idea of "encode a check in the constraints" to its literal logical extreme, Distiller exposes many new opportunities for constraint reduction, resulting in cost reductions for benchmark computations of 1.3–50×, and in some cases, better asymptotics.
Ring Confidential Transaction (RingCT) protocol is an effective cryptographic component for preserving the privacy of cryptocurrencies. However, existing RingCT protocols are instantiated from one-out-of-many proofs with only one secret, leading to low efficiency and weak anonymity when handling transactions with multiple inputs. Additionally, current partial knowledge proofs with multiple secrets are neither secure nor efficient to be applied in a RingCT protocol.In this paper, we propose a novel any-out-of-many proof, a logarithmic-sized zero-knowledge proof scheme for showing the knowledge of arbitrarily many secrets out of a public list. Unlike other partial knowledge proofs that have to reveal the number of secrets [ACF21], our approach proves the knowledge of multiple secrets without leaking the exact number of them. Furthermore, we improve the efficiency of our method with a generic inner-product transformation to adopt the Bulletproofs compression [BBB+18], which reduces the proof size to 2⌈log2(N)⌉+9.Based on our proposed proof scheme, we further construct a compact RingCT protocol for privacy cryptocurrencies, which can provide a logarithmic-sized communication complexity for transactions with multiple inputs. More importantly, as the only known RingCT protocol instantiated from the partial knowledge proofs, our protocol can achieve the highest anonymity level compared with other approaches like Omniring [LRR+19]. For other applications, such as multiple ring signatures, our protocol can also be applied with some modifications. We believe our techniques are also applicable in other privacy-preserving scenarios, such as multiple ring signatures and coin-mixing in the blockchain.
Cryptography and Data Security
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Michael L. Rosenberg, Jacob White, Christina Garman, Ian Miers
Frequently, users on the web need to show that they are, for example, not a robot, old enough to access an age restricted video, or eligible to download an ebook from their local public library without being tracked. Anonymous credentials were developed to address these concerns. However, existing schemes do not handle the realities of deployment or the complexities of real-world identity. Instead, they implicitly make assumptions such as there being an issuing authority for anonymous credentials that, for real applications, requires the local department of motor vehicles to issue sophisticated cryptographic tokens to show users are over 18. In reality, there are multiple trust sources for a given identity attribute, their credentials have distinctively different formats, and many, if not all, issuers are unwilling to adopt new protocols.We present and build zk-creds, a protocol that uses general-purpose zero-knowledge proofs to 1) remove the need for credential issuers to hold signing keys: credentials can be issued to a bulletin board instantiated as a transparency log, Byzantine system, or even a blockchain; 2) convert existing identity documents into anonymous credentials without modifying documents or coordinating with their issuing authority; 3) allow for flexible, composable, and complex identity statements over multiple credentials. Concretely, identity assertions using zk-creds take less than 150ms in a real-world scenario of using a passport to anonymously access age-restricted videos.
While the Internet of things brings convenience to people's lives, it will also bring people hidden worries about data security. As an important barrier to protect data security, identity authentication is widely used in the Internet of things. However, it is necessary to protect users' identity privacy while authenticating their identity. Anonymous authentication technology is often used to solve the contradiction between legitimacy and privacy in the authentication process. The existing anonymous authentication scheme has many problems in practical application such as the inability to achieve complete anonymity, the high computational complexity of the algorithm, and the corruption of the central authority. Aiming at the privacy of authentication, we propose Zero-Cerd, a self-blindable anonymous authentication system based on blockchain and dynamic accumulator. The self-blinding properties of the credential enable the users themselves to generate a new validly pseudonymous credential. With the help of zero-knowledge proof technology, users can prove the validity of their credentials without disclosing any information. Security analysis shows that our scheme has achieved the expected security objectives. Compared with the existing schemes, our scheme has the advantages of complete anonymity and high efficiency, and is more suitable for IoT applications with privacy protection requirements.
In recent years, permissionless blockchains have gained significant attention for their ability to secure and provide transparency in transactions. The development of blockchain technology has shifted from cryptocurrency to decentralized finance, benefiting millions of unbanked individuals, and serving as the foundation of Web3, which aims to provide the next generation of the internet with data ownership for users. The rise of NFTs has also helped artists and creative workers to protect their intellectual property and reap the benefits of their work. However, privacy risks associated with permissionless blockchains have become a major concern for individuals and institutions. The role of blockchain in the transition from Web2 to Web3 is crucial, as it is rapidly evolving. As more individuals, institutions, and organizations adopt this technology, it becomes increasingly important to closely monitor the new risks associated with permissionless blockchains and provide updated solutions to mitigate them. This paper endeavors to examine the privacy risks inherent in permissionless blockchains, including Remote Procedure Call (RPC) issues, Ethereum Name Service (ENS), miner extractable value (MEV) bots, on-chain data analysis, data breaches, transaction linking, transaction metadata, and others. The existing solutions to these privacy risks, such as zero-knowledge proofs, ring signatures, Hyperledger Fabric, and stealth addresses, shall be analyzed. Finally, suggestions for the future improvement of privacy solutions in the permissionless blockchain space shall be put forward.
As digital payments become increasingly ubiquitous, concerns over data privacy and transaction security have intensified, prompting the need for privacy-preserving payment architectures. This study explores the design, implementation, and evaluation of payment systems that ensure confidentiality, integrity, and anonymity without compromising transactional efficiency or regulatory compliance. It examines key technologies such as homomorphic encryption, secure multiparty computation, zero-knowledge proofs, and blockchain-based mechanisms that enable secure payment verification and data sharing with minimal exposure of sensitive user information. Furthermore, it highlights privacy-enhancing frameworks integrated into mobile wallets, digital identity systems, and decentralized finance (DeFi) platforms. Through comparative analysis of centralized and decentralized payment models, the paper identifies trade-offs between scalability, transparency, and privacy assurance. The findings underscore that hybrid architectures—combining cryptographic privacy layers with compliance-enabling audit trails—represent the most viable approach for future financial ecosystems. Ultimately, privacy-preserving payment architectures not only safeguard user trust but also support regulatory adaptability and sustainable innovation in the evolving landscape of digital finance.
Smart contracts self-executing code deployed on blockchain platforms have revolutionized the way digital agreements are formed and executed. Despite their decentralized nature and deterministic logic, vulnerabilities in code and execution environments can compromise their security. Cryptography is pivotal in safeguarding the integrity, authenticity, and confidentiality of smart contract operations. This paper explores cryptographic techniques that enhance smart contract trustworthiness, including digital signatures, zero-knowledge proofs, and verifiable computation. We assess how these methods reinforce security, compare frameworks across criteria like scalability and auditability, and present best practices for secure smart contract development
Cristina Vilchez Moya, Juan Ramón Bermejo Higuera, Juan Ramón Bermejo Higuera, Javier Bermejo Higuera · 6 authors
The problem of digital identity acquires more relevance every day in the eyes of a society that spends more and more time connected to the Internet. It has evolved throughout its history to reach a decentralized model known as Self-Sovereign Identity (SSI), which finds its natural tools in the blockchain technology and Zero-Knowledge Proofs (ZKPs). ZKPs, in this context, allow users to prove that their credentials are legitimate without revealing more information than is strictly necessary, and constitute one of the most promising areas of applied cryptography. In this work, an application is developed for the study of Zero-Knowledge Proof methods and, specifically, in their application for authentication in public-private key encryption systems. It focuses on the study of three ZKP protocols (Feige-Fiat-Shamir, Guillou-Quisquater, and Schnorr, which rely on the problems of large number factorizations and discrete logarithms for security) in the practical use-case where a prover wants to demonstrate knowledge of a private key for a public key without revealing the key itself. The application allows the user to modify the necessary parameters in each method to achieve a better understanding of their role in their safety and efficiency. Several types of attacks are carried out against the above-mentioned protocols to analyze their degree of security and what recommendations can be made to improve it.
The double-spending problem in blockchain technology is a significant challenge that threatens the integrity and trustworthiness of decentralized systems. This problem occurs when a user attempts to spend the same cryptocurrency unit twice, leading to a situation where the blockchain network must decide which transaction to accept and which to reject. One of the most urgent problems with blockchain technology is the issue of double spending, as it undermines the fundamental principles of trust and transparency that underlie decentralized systems. Various factors can contribute to the double-spending problem, including network latency, malicious actors, and the consensus mechanism used to validate transactions. This study investigates the many approaches put out to solve the double-spending issue in blockchain technology. The proof-of-work consensus mechanism, which necessitates network users to carry out difficult calculations in order to validate transactions, is one of the most popular alternatives. The proof-of-stake consensus technique is an additional remedy, which relies on participants staking their cryptocurrency units to validate transactions. While both mechanisms have their advantages and disadvantages, they are not foolproof and can be vulnerable to attacks. Emerging technologies, like multi-party computation and zero-knowledge proofs, are being investigated in addition to current solutions to the double-spending issue. Overall, this paper highlights the critical nature of the double-spending problem in blockchain technology and evaluates the existing and emerging solutions to the issue.
In the past few years, Internet users are at danger due to the exponential surge in cyberattacks. Given the importance of privacy techniques like zero-knowledge proof (ZKP), their study and development are the major areas of interest. A cryptographic method called ZKPs can conceal information while still enabling data validation. In this work, we outline various schemes highlighting the value of zero-knowledge evidence in the context of cyber security and how it can reduce the risk of cyberattacks. We have discussed two models of ZKPs, which are interactive and noninteractive ZKPs with their applications and issues. The goal of this research is to develop communication- and computation-efficient protocols for zero-knowledge arguments and proofs of propositions that include a significant number of “simple” predicates. The study finishes with real-world examples, practicality, and usability of ZKP applications using blockchain, zk-SNARKs, zk-STARKs, and the cryptocurrency Zcash.
Abstract Blockchain and Decentralized Applications (DApps) are increasingly important for creating trust and transparency in data storage and computation. However, on-chain transactions are often costly and slow. To overcome this challenge, off-chain nodes can be used to store and compute data. Unfortunately, this introduces the risk of untrusted nodes. To address this, authenticated data structures have been proposed, however, this ignores the compute of data from the raw data. We tackle this challenge by introducing zk-Oracle, which provides an efficient and trusted compute and storage off-chain. There is a challenge in using zero-knowledge proofs (zk-proof for short), which is the large proof generation time. We aim to overcome it with novel designs in zk-Oracle. zk-Oracle builds on zk-proofs technologies to achieve two goals. First, the computation of data structures from raw data and the corresponding proof generation is improved in terms of performance. Second, the verification on-chain is inexpensive and fast. Our experiments show that we can speed up zk-proof generation by up to $$550 \times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>550</mml:mn> <mml:mo>×</mml:mo> </mml:mrow> </mml:math> faster than the baseline method.
Xin Liu, Xiaomeng Liu, Naixue Xiong, Dan Luo · 6 authors
With the rapid development of cloud computing and other modern technologies, collaborative computing between data is increasing, and privacy protection and secure multi-party computation are also attracting more attention. The emergence of cloud computing provides new options for data holders to perform complex computing problems and to store images; however, data privacy issues cannot be ignored. If a graphic is encrypted and stored in the cloud, the cloud server will perform confidential similar matching when the user searches. At present, most research on searchable encryption is focused on text search, with few schemes researched on how to finish the graphic search. To solve this problem, this paper proposes a secure search protocol based on graph shape under the semi-honest model. Using the cut-choose method and zero-knowledge proof, further designs of the anti-malicious attack graphic similarity judgment system (AAJS) based on the Paillier encryption algorithm, can achieve the secure search and matching of the graph while resisting malicious adversary attacks. The proposed protocol’s security is proved by the real/ideal model paradigm. This paper conducts performance analysis and experimental simulation on the existing scheme and the experiments demonstrate that the system achieves high execution efficiency.
In this paper, we propose a physical protocol to verify the first nonzero term of a sequence using a deck of cards. The protocol lets a prover show the value of the first nonzero term of a given sequence to a verifier without revealing which term it is. Our protocol uses $Θ(1)$ shuffles, which is asymptotically lower than that of an existing protocol of Fukusawa and Manabe which uses $Θ(n)$ shuffles, where $n$ is the length of the sequence. We also apply our protocol to construct zero-knowledge proof protocols for three well-known logic puzzles: ABC End View, Goishi Hiroi, and Toichika. These protocols enables a prover to physically show that he/she know solutions of the puzzles without revealing them.