Non-interactive Zero-knowledge Proofs Research Articles

A Comprehensive Approach to User Delegation and Anonymity within Decentralized Identifiers for IoT.

Decentralized Identifiers have recently expanded into Internet of Things devices and are crucial in securing users' digital identities and data. However, Decentralized Identifiers face challenges in scenarios necessitating authority delegation and anonymity, such as when dealing with legal guardianship for minors, device loss or damage, and specific medical contexts involving patient information. This paper aims to strengthen data sovereignty within the Decentralized Identifier system by implementing a secure authority delegation and anonymity scheme. It suggests optimizing verifiable presentations by utilizing a sequential aggregate signature, a Non-Interactive Zero-Knowledge Proof, and a Merkle tree to prevent against linkage and Sybil attacks while facilitating delegation. This strategy mitigates security risks related to delegation and anonymity, efficiently reduces the computational and verification efforts for signatures, and reduces the size of verifiable presentations by about 1.2 to 2 times.

A logarithmic-sized accountable ring signature scheme in the standard model

Ring signature and group signature are two major cryptographic primitives providing users anonymity and authentication simultaneously. While both primitives enable any user to sign messages as a member of a set of users, the feature of ring signature is that a signer can choose a group in an ad-hoc manner, which is called a ring, by itself. Conversely, in group signature, a group membership is managed by some trusted third party, which is called a group manager, and an (appropriate) accountability is provided for the group manager to identify illegal anonymous signers. Accountable ring signature (ARS) is a cryptographic primitive combining the features of ring signature and group signature. ARS allows signers to choose their groups (rings) in an ad-hoc manner, and at the same time, maintain accountability by forcing them to select a designated opener who can identify them.In this paper, we propose the first ARS scheme with O(log⁡n) signature size in the standard model (without depending on the random oracle methodology), where n is the size of a ring. More precisely, we propose a new generic construction of ARS based on (standard) signature, (standard) public key encryption, non-interactive zero-knowledge proof system, somewhere perfectly binding hash function, and public key encryption with non-interactive opening. All building blocks for our ARS scheme can be obtained under the decisional linear (DLIN) assumption over bilinear groups.

Sphinx-in-the-Head: Group Signatures from Symmetric Primitives

Group signatures and their variants have been widely used in privacy-sensitive scenarios such as anonymous authentication and attestation. In this paper, we present a new post-quantum group signature scheme from symmetric primitives. Using only symmetric primitives makes the scheme less prone to unknown attacks than basing the design on newly proposed hard problems whose security is less well-understood. However, symmetric primitives do not have rich algebraic properties, and this makes it extremely challenging to design a group signature scheme on top of them. It is even more challenging if we want a group signature scheme suitable for real-world applications, one that can support large groups and require few trust assumptions. Our scheme is based on MPC-in-the-head non-interactive zero-knowledge proofs, and we specifically design a novel hash-based group credential scheme, which is rooted in the SPHINCS+ signature scheme but with various modifications to make it MPC (multi-party computation) friendly. The security of the scheme has been proved under the fully dynamic group signature model. We provide an implementation of the scheme and demonstrate the feasibility of handling a group size as large as 2 60 . This is the first group signature scheme from symmetric primitives that supports such a large group size and meets all the security requirements.

Enhancing Security and Flexibility in the Industrial Internet of Things: Blockchain-Based Data Sharing and Privacy Protection

To address the complexities, inflexibility, and security concerns in traditional data sharing models of the Industrial Internet of Things (IIoT), we propose a blockchain-based data sharing and privacy protection (BBDSPP) scheme for IIoT. Initially, we characterize and assign values to attributes, and employ a weighted threshold secret sharing scheme to refine the data sharing approach. This enables flexible combinations of permissions, ensuring the adaptability of data sharing. Subsequently, based on non-interactive zero-knowledge proof technology, we design a lightweight identity proof protocol using attribute values. This protocol pre-verifies the identity of data accessors, ensuring that only legitimate terminal members can access data within the system, while also protecting the privacy of the members. Finally, we utilize the InterPlanetary File System (IPFS) to store encrypted shared resources, effectively addressing the issue of low storage efficiency in traditional blockchain systems. Theoretical analysis and testing of the computational overhead of our scheme demonstrate that, while ensuring performance, our scheme has the smallest total computational load compared to the other five schemes. Experimental results indicate that our scheme effectively addresses the shortcomings of existing solutions in areas such as identity authentication, privacy protection, and flexible combination of permissions, demonstrating a good performance and strong feasibility.

Temporal ECDSA: A timestamp and signature mask enabled ECDSA algorithm for IoT client node authentication

Internet of Things (IoT) networks are vulnerable to various security threats, especially in client authentication. The current authentication methods require significant resources and are vulnerable to specific attacks. The Non-Interactive Zero Knowledge Proof (NIZKP) concept suits IoT device authentication. Elliptic Curve Digital Signature (ECDSA) is a popular algorithm for IoT device authentication based on elliptic curve cryptography (ECC) and NIZKP. However, an intelligent attacker who captures the ECDSA signatures generated by the same random number can recover the private key. This paper proposes a timestamp based approach to prevent signature reuse and fake signature generation in the ECDSA algorithm. The signature proof is generated differently at each occurrence to prevent the generation of valid signatures from leaked private keys. The proposed approach eliminates the expensive modular inversion operations in signature generation and verification phases, enhancing execution efficiency. The analysis results indicate that the proposed Temporal ECDSA algorithm effectively prevents most attacks on client authentication in IoT networks. Various metrics, including computational complexity and security measures, were used to evaluate the effectiveness of the proposed approach, demonstrating that it outperforms most ECDSA variants.

Device-independent quantum randomness-enhanced zero-knowledge proof.

Zero-knowledge proof (ZKP) is a fundamental cryptographic primitive that allows a prover to convince a verifier of the validity of a statement without leaking any further information. As an efficient variant of ZKP, noninteractive zero-knowledge proof (NIZKP) adopting the Fiat-Shamir heuristic is essential to a wide spectrum of applications, such as federated learning, blockchain, and social networks. However, the heuristic is typically built upon the random oracle model that makes ideal assumptions about hash functions, which does not hold in reality and thus undermines the security of the protocol. Here, we present a quantum solution to the problem. Instead of resorting to a random oracle model, we implement a quantum randomness service. This service generates random numbers certified by the loophole-free Bell test and delivers them with postquantum cryptography (PQC) authentication. By employing this service, we conceive and implement NIZKP of the three-coloring problem. By bridging together three prominent research themes, quantum nonlocality, PQC, and ZKP, we anticipate this work to inspire more innovative applications that combine quantum information science and the cryptography field.

A Privacy-Preserving Internet of Things Smart Healthcare Financial System

Several emerging areas like sensor networks, the Internet of Things (IoT), and distributed networks are gaining traction where resource-constrained devices communicate by sharing privacy-preserving information. Due to heavy cryptographic components, standard cryptographic algorithms do not fit these IoT devices. In this paper, we propose an efficient zero-knowledge blockchain-based privacy-preserving decentralized healthcare finance system that is suitable for lightweight computer devices. The proposed design mainly focuses on non-interactive zero-knowledge proof, which substantially reduces the cost of communication between two devices. We explain the system framework and its use case for a healthcare financial system at a micro-level. However, it can also be extended easily to more general financial systems. Our system framework is efficient and lightweight, using more efficient zero-knowledge-based proofs; validation of the transactions is done in milliseconds. As an advancement to our work, the proposed healthcare financial system for lightweight computer devices is also auditable without leaking any extra information than required.

Obtaining simulation extractable NIZKs in the updatable CRS model generically

Non-interactive zero-knowledge proofs as well as succinct non-interactive argument of knowledge (SNARK) are playing a central role in both theory and application of cryptography. Simulation extractable for SNARKs is considered a necessary security requirement by most applications which prevents the protocol from malleable attacks. However, a trusted party is required to generate the common reference string (CRS) for SNARKs which can be quite problematic in real applications. Recently, the subvertible and updatable CRS model has been proposed to relax the trust in the CRS generation procedure.In this paper, we propose two generic compilers that can achieve simulation extractable in the updatable CRS model. By using an efficient updatable verifiable random function defined in this paper which may be of independent interest, we show that our compiler can lift the updatable knowledge soundness of the underlying SNARKs to achieve updatable simulation extractability. We extend our results by proposing another compiler that can lift a NIZK that has an even weaker security notion called updatable soundness to achieve updatable simulation extractability. We instantiate our compilers and compare them to other related works. This shows that our efficient compilers can be used in various applications.

Redactable consortium blockchain based on verifiable distributed chameleon hash functions

With the evolving application demands, the inherent immutability of consortium blockchains hinders their widespread adoption. For example, expired data stored on the chain cannot be deleted, and erroneous data cannot be redacted, seriously limiting the flexibility of consortium blockchains. However, existing redactable blockchain solutions need to be improved in aspects of decentralization, efficiency, and fault tolerance. This paper develops a new verifiable distributed chameleon hash (VDCH) function to solve the above problems. With VDCH, nodes share chameleon keys with a secure multi-party computation protocol based on a verifiable key-sharing scheme, and the collision shares can be verified with a Schnorr non-interactive zero-knowledge proof protocol, which enhances the fault tolerance of the consortium chain while maintaining its decentralized nature. Then, this paper proposes a consensus protocol called CVTSS based on verifiable threshold signatures, which provides protocol support for collaborative hash collision computation by multiple nodes using VDCH, thus avoiding the dependence on Nakamoto consensus and improving the redaction efficiency. Meanwhile, CVTSS uses threshold signatures to prevent malicious nodes from tampering with data using one-time chameleon keys. Finally, this paper constructs an efficient, practical, and secure redactable consortium chain scheme based on VDCH and CVTSS. Theoretical analysis and experimental results show that the proposed scheme can operate safely in the presence of malicious nodes with an acceptable time cost.

Research on security access authentication mechanism of intelligent sensor based on non-interactive zero-knowledge proof method

In order to study the standard security access authentication mechanism of intelligent sensing terminals of massive power Internet of Things, In order to study the standard secure access authentication mechanism of intelligent sensing terminal of massive power Internet of Things, a new privacy protection method widely used in block chain is proposed to prove identity. The traditional power IoT cloud-side interaction security access MQTT protocol still has a lot of room for adaptation and optimization. First, the proposed non-interactive zero-knowledge proof identity authentication method reduces the time of traditional standard secure access authentication process; Second, it reduced the computing resources consumed in a large number of intelligent sensors access authentication. The comparison results show that, the access authentication time of this method is 30%∼50% less than that of the traditional secure access authentication process. The computing resources consumed during authentication are reduced by 20% to 30% compared with traditional security and secrecy mechanisms.

Efficient and Flexible Multiauthority Attribute-Based Authentication for IoT Devices

The correctness and reliability of data sources are the keys to the practicality of data collected by IoT devices. Attribute-based signature(ABS) is a cryptographic primitive for users to sign with their own attributes, which can be applied to the authentication process in IoT scenarios. The attribute authority is responsible for issuing the attribute key to the user in ABS. Multiple authorities can complete attribute management tasks to avoid the threat of a single authority. However, attribute authorities need to execute multiple interactions to collaborate to generate attribute keys for users, which brings a large transmission burden. In addition, a lot of resource-constrained terminals in the IoT mostly play the role of signer or verifier in authentication protocols. The signature generation and verification algorithms often have heavy pairing and exponentiation operations. Currently, no ABS scheme takes into account the efficiency of all participating entities simultaneously. In this paper, we present an aggregated anonymous key issue (AAKI) protocol to reduce the transmission burden between multiple authorities. Meanwhile, the non-interactive zero-knowledge proof aggregate exponentiation (NI-ZKPoKAE) protocol is designed to aggregate the transmitted secret values in AAKI. To reduce the computational burden of signers and verifiers, Blakley secret sharing, where the Hadamard matrix is used more efficiently to handle the (n,n)-threshold, is used to construct an efficient and fine-grained multi-authority ABS (EFMA-ABS) scheme. This brings high efficiency to all three types of parties involved in IoT authentication. Our above-mentioned protocols have been proven to be feasible and effective.

A Blockchain-Based Copyright Protection Scheme With Proactive Defense

Copyright protection, including copyright registration, copyright transfer and infringement penalty, plays a critical role in preventing illegal usage of original works. The mainstream traditional copyright protection schemes need an authority online all the time to handle copyright issues and face some problems such as intricate copyright transfer, single point of failure and so on. To alleviate the burden of the authority, a few blockchain-based copyright protection schemes are proposed. However, most of them do not consider copyright transfer, and their infringement penalty may only happen after copyright owners discover the infringement behavior (i.e., “ex-post penalty”). In this article, we propose a new security strategy, called “Proactive Defense” in copyright protection which can prevent infringement before it occurs. With our proposed proactive defense strategy, we design a secure copyright protection scheme which provides advantages of compact copyright transfer and prior infringement penalty. More concrete, both copyright registration and transfer are regarded as transactions and recorded to the blockchain. Based on the double-authentication-prevention signature and non-interactive zero-knowledge proof techniques, illegal copyright transfer can be detected and the infringement penalty can be done automatically with a tailored smart contract before the completion of the transfer. Our security analysis shows that the proposed scheme can achieve all desirable security properties. Moreover, we implement our scheme in Java and evaluate the performance experimentally. Experimental results show that the proposed scheme has good security and efficiency, which can be applied for the copyright protection.

Robust Subgroup Multisignature with One-Time Public Keys in Order

Robust subgroup multisignature allows any subgroup of signers from a global set to sign a given message on behalf of the whole group, and the individual signatures should be verified before the combination process, which resists poison signature attacks. An emerging application of robust subgroup multisignatures in blockchain is that a qualified subgroup of a global set of users has reached agreement. In the integrated blockchain and edge computing system, the edge server can naturally act as a combiner in multisignatures and help other end devices produce the final aggregate signature. In this paper, we propose a robust subgroup multisignature with one-time public keys in order that has two advantages for solving the signers ordering problem and one-time public key problem simultaneously. Our scheme is a nontrivial extension of Galindo et al.’s robust subgroup multisignature scheme and can be proven unforgeable, robust and chronological in random oracles. Our scheme can also be suitable for the consortium blockchain by adding a noninteractive zero-knowledge (NIZK) proof system for certifying the one-time public keys.

PRI: PCH-based privacy-preserving with reusability and interoperability for enhancing blockchain scalability

Blockchain systems, one of the most popular distributed systems, are well-applied in various scenarios, e.g., logistics and finance. However, traditional blockchain systems suffer from scalability issues. To tackle this issue, Payment Channel Hubs (PCHs) are proposed. Recent efforts, such as A2L (SP'21) and Teechain (SOSP'19), enhance the privacy, reusability, and interoperability properties of PCHs. Nevertheless, these solutions have intrinsic limitations: they rely on trusted hardware or suffer from the deposit lock-in problem. Furthermore, the functionalities of some of these solutions are restricted to fixed-amount payments and do not support multi-party participation. These aforementioned problems limit their capabilities to alleviate blockchain scalability issues. In this paper, we propose PRI, a novel PCH solution that simultaneously guarantees transaction Privacy (i.e., relationship unlinkability and value confidentiality), deposit Reusability, and blockchain Interoperability, which can mitigate the aforementioned problems. PRI is constructed by several new building blocks, including (1) an atomic deposit protocol that enforces user and hub to deposit equivalent assets in a shared address for building a fair payment channel; (2) a privacy-preserving deposit certification scheme that leverages the Pointcheval and Sanders signature and non-interactive zero-knowledge proof to resolve the deposit lock-in issue in maintaining payment channels; (3) a range proof which ensures the legality and confidentiality of transaction values. We conduct extensive experimental evaluations of PRI, demonstrating that it improves the state-of-the-art approaches in terms of performance.

Simulatable verifiable random function from the LWE assumption

A verifiable random function (VRF) is a pseudorandom function F that can be publicly verified. A simulatable VRF (sVRF) is an important variant of a VRF, which additionally provides simulatability. Informally, the simulatability of a VRF depicts the ability to simulate a valid proof π that y=F(sk,x) for any input x and any output value y. A (simulatable) VRF can be used in the E-Cash, E-Lottery, blockchain and constructing the multi-theorem non-interactive zero-knowledge (NIZK) proof. However, up to now, the existing constructions of an sVRF either rely on non-standard assumptions (e.g., the Q-type ones), or are built in the random oracle model, or resort to time-consuming techniques like the Cook-Levin reduction.In this paper, we design the first sVRF from the LWE assumption in the standard model (free of a random oracle) without using a Cook-Levin reduction. In our construction of an sVRF, we take as building blocks a pseudorandom function, a trapdoor fully homomorphic commitment (FHC) scheme, and a NIZK proof system for a language specified by FHC. Our trapdoor FHC is the key technical tool, which helps the simplification of the underlying NIZK language, thus making possible an instantiation of a NIZK proof from LWE without a Cook-Levin reduction. Together with an LWE-based PRF, we obtain an sVRF scheme from LWE.

Time Controlled Expressive Predicate Query With Accountable Anonymity

Many existing searchable encryption schemes are inflexible in retrieval patterns. The data usage authorization is almost permanent valid as long as the user is not revoked. This “all-or-nothing” authorization mode is not compatible with the “pay-as-you-use” commercial billing model. In this article, we propose a new notion called time controlled expressive predicate query with accountable anonymity. It realizes time controlled data query, where a time server issues time token to authorize search privilege in designated time period. The data users can anonymously query on encrypted data and the anonymity is accountable in a way that the trusted authority is able to deanonymize data users if they misbehave in the system. The underlying techniques are anonymous credential, Pederson commitment and non-interactive zero-knowledge proof. We firstly design an efficient expressive predicate query (EPQ) scheme, which is proved secure to protect the privacy of expressive search predicate. Based on EPQ, we present a concrete system instantiation, which realizes key-escrow free and time token nontransferability. The formal definition and security models are given out. The system is formally proved indistinguishable against chosen keyword-set attacks, unforgeable of time tokens and accountable of anonymous users. The comparison and experiment results demonstrate its scalability and efficiency.

Enabling Regulatory Compliance and Enforcement in Decentralized Anonymous Payment

Decentralized anonymous payment (DAP) enables users to directly transfer cryptocurrencies privately without passing through a central authority. Anonymous cryptocurrencies have been proposed to improve the privacy degree of DAP systems, such as Zerocash and Monero. However, the strong degree of privacy may cause new regulatory concerns, i.e., the anonymity of transactions can be used for illegal activities, such as money laundering. In this paper, we propose a novel DAP scheme that supports regulatory compliance and enforcement. We first introduce regulators into the system, who define regulatory policies for anonymous payment, and the policies are enforced through commitments and non-interactive zero-knowledge proofs for compostable statements. By doing so, users can prove that transactions are valid and comply with regulations. A tracing mechanism is embedded in the scheme to allow regulators to recover the real identities of users when suspicious transactions are detected. The formal security model and proof are provided to demonstrate that the proposed scheme can achieve desired security properties, and the performance evaluation shows its high efficiency.

Group signatures and more from isogenies and lattices: generic, simple, and efficient

We construct an efficient dynamic group signature (or more generally an accountable ring signature) from isogeny and lattice assumptions. Our group signature is based on a simple generic construction that can be instantiated by cryptographically hard group actions such as the CSIDH group action or an MLWE-based group action. The signature is of size O(log N), where N is the number of users in the group. Our idea builds on the recent efficient OR-proof by Beullens, Katsumata, and Pintore (Asiacrypt’20), where we efficiently add a proof of valid ciphertext to their OR-proof and further show that the resulting non-interactive zero-knowledge proof system is online extractable. Our group signatures satisfy more ideal security properties compared to previously known constructions, while simultaneously having an attractive signature size. The signature size of our isogeny-based construction is an order of magnitude smaller than all previously known post-quantum group signatures (e.g., 6.6 KB for 64 members). In comparison, our lattice-based construction has a larger signature size (e.g., either 126 KB or 89 KB for 64 members depending on the satisfied security property). However, since the O(cdot )-notation hides a very small constant factor, it remains small even for very large group sizes, say 2^{20}.

BP-AKAA: Blockchain-enforced Privacy-preserving Authentication and Key Agreement and Access Control for IIoT

The Industrial Internet of Things (IIoT) links multiple subnets to accomplish more real-time, efficient, and high-class production. Authentication is an essential prerequisite for secure communication and data sharing between mutually untrusted subdomains.However, solving trust issues between subnets through third-party trusted servers inevitably introduces security and efficiency bottlenecks. In addition, the issue of not compromising the privacy of mutual authentication remains a challenge. Furthermore, key agreement and access control, as two follow-up steps of authentication, is non-negligible for achieving secure and efficient data sharing. Existing authentication works either require heavy computational overhead or lack necessary features for data sharing. Therefore, this paper proposed a blockchain-enforced cross-domain private-protected authentication and key agreement scheme supporting attribute-based access control, named BP-AKAA. To the best of our knowledge, this is the first scheme that simultaneously supports privacy authentication, key agreement, and access control. Non-interactive zero-knowledge proof technology is adopted to protect the identities of devices. In addition, with the assistance of distributed blockchain, the untrust issue of cross-domain authentication is solved.Performance analysis demonstrates that our scheme satisfies multiple functions, including cross-domain, privacy-preserving, and mutual authentication, and outperforms existing schemes in terms of key generation, authentication, and access control.

A Privacy and Efficiency-Oriented Data Sharing Mechanism for IoTs

With the volume of data increasing in the Internet of Things, a new business mode, where data owners share their own data to others for rewards, has emerged. Therefore, how to motivate data owners to participate in the data trading process is the main challenge. So far, lots of works focus on the motivation mechanism designing and ensure a fair distribution of profits among data owners. However, some security and privacy issues are still not well solved and the data owners are still unwilling to participate in the process. Especially, when a data provider claims rewards with its real identity for the shared data, the linkage between its real identity and the shared data will expose the participator's private information included in the shared data, such as location information. To protect user's privacy in the scenario, a privacy and efficiency-oriented data sharing mechanism for IoTs is proposed in this paper. We first propose a blockchain-based data sharing framework in which the behavior of all participants will be supervised. Then, in order to hide the real identities of data providers during the data sharing process, an anonymous certificate-based data sharing policy is proposed. At last, two novel non-interactive zero-knowledge proofs are designed to hide the identities of qualified data providers while claiming rewards to the system. Through security analysis and performance evaluation, the feasibility and effectiveness of the data sharing scheme are illustrated.