Modern Public Key Infrastructures (PKIs) allow users to create and maintain centrally stored cryptographic certificates. These infrastructures use a so-called certificate chain. At the root of the chain, a root Certification Authority (CA) is responsible for issuing the base certificate. Every verification and certification step within the chain is based upon the security of said root CA. Thus, its operation security is of great concern. Since the root certificates are stored locally on the root CA, any Denial of Service (DoS) attack may render the whole certificate chain, which is based on of the attacked root CA, inoperable. Therefore, this article evaluates different approaches to a decentralized data storage system that is based on the Distributed Ledger Technology (DLT). To show the real-world potential of the proposed approaches, we also evaluate the different technologies using a novel PKI mechanism called Near Field Communication Key Exchange (NFC-KE). The results indicate that modern distributed data storage solutions such as Interplanetary Filesystem (IPFS) and SIA can have significant performance and decentralization benefits in comparison to purely Blockchain-based technologies like Hyperledger Fabric. However, they lack any Smart Contract functionality, which requires a software developer to implement verification mechanisms in centralized software solutions.
Xin Liu, Xiaomeng Liu, Ruiling Zhang, Dan Luo · 6 authors
Manhattan distance is mainly used to calculate the total absolute wheelbase of two points in the standard coordinate system. The secure computation of Manhattan distance is a new geometric problem of secure multi-party computation. At present, the existing research secure computing protocols for Manhattan distance cannot resist the attack of malicious participants. In the real scene, the existence of malicious participants makes it necessary to study a solution that can resist malicious attacks. This paper first analyzes malicious attacks of the semi-honest model protocol of computing Manhattan distance and then designs an advanced protocol under the malicious model by using the Goldwasser–Micali encryption system and Paillier encryption algorithm, and utilizing some cryptographic tools such as the cut-choose method and zero-knowledge proof. Finally, the real/ideal model paradigm method is used to prove the security of the malicious model protocol. Compared with existing protocols, the experimental simulation shows that the proposed protocol can resist malicious participant attacks while maintaining high efficiency. It has practical value.
Abstract Today, with the growth of cryptocurrencies, the importance of keeping them has increased. Wallets are one of the ways to keep cryptocurrencies safe. One of the techniques for securing cryptocurrency wallets is the use of multi-signature technique. This technique is based on a concept called secret sharing. In order to ensure the security of these wallets, the secret sharing scheme is used, which uses the Lagrange interpolation algorithm. This algorithm has a challenge in terms of time complexity, and in this research, we introduced two parallel approaches to reduce this time complexity based on graphical processor units (GPU) and distributed systems. In addition to reducing the time complexity, the distributed approach was able to help us increase the security of the algorithm. The speedup obtained from the execution on the interpolation of 16384 points in the GPU-based approach was equal to 45214 and in the distributed approach, in the execution resulting from 4 to 128 processes was equal to 7.81.
A proof-of-randomness (PoR) protocol is presented as a fair and low energy-cost consensus mechanism for blockchains. Each network node of a blockchain may use a true random number generator (TRNG) and hash algorism to fulfil the PoR protocol. In this paper, we give the consensus mechanism of the PoR protocol, and classify it into a new kind of randomized algorithms called Macau. The PoR protocol could generate a blockchain without any competition of computing power or stake of cryptocurrency. Besides, we give some advantages of integrating quantum random number generator (QRNG) chips into hardware wallets, and also discuss the way to cooperate with quantum key distribution (QKD) technology.
The control of future power grids is migrating from a centralized to a distributed/decentralized scheme to enable a massive penetration of distributed energy resources and bring extreme enhancements of autonomous operations in terms of grid resilience, security, and reliability. Most effort has been on the design of distributed/decentralized controllers; however, the guarantees of the proper execution of the controls are also essential but relatively less emphasized. A common assumption is that local controllers would fully follow the designated controller dynamics based on the data received from communication channels. Such an assumption could be risky because proper execution of the controller dynamics is then built on trust in secure communication and computation. On the other hand, it is impractical for a verifier to repeat all the computations involved in the controls to verify the computational integrity. In this work, we leverage a type of cryptography technology, known as zero-knowledge scalable transparent arguments of knowledge to verify the computational integrity of control algorithms, such that verifiers can check the computational integrity with much less computational burden. The method presented here converts the challenge of data integrity into a subset of computational integrity. In this proof-of-concept paper, our focus will be on projected linear dynamics that are commonly seen in distributed/decentralized power system controllers. In particular, we have derived polynomial conditions in the context of zk-STARKs for the projected linear dynamics.
Nabeel Khan, Hanan Aljoaey, Mujahid Tabassum, Ali Farzamnia · 6 authors
Since cloud computing is an essential component of any modern company (usually accounting for a considerable share of information technology (IT) infrastructure investment), consumers rely on cloud services. Data privacy and security are worries when data remains in third-party storage. Existing document version control systems are centralized and at risk from data loss, as seen by higher time utilization and incorrect document update procedures that allow modifications to a document without the awareness of other network operators. Underutilized peer resources might be leveraged to construct storage. According to this argument, an elevated level of data security may be obtained by encrypting the data and dispersing it among numerous nodes. In this study, we attempted to review the security of cloud systems when using the blockchain Ethereum, and cloud computing was briefly discussed with its advantages and disadvantages. The idea of a decentralized cloud was briefly demonstrated with blockchain technology. Furthermore, previous papers were reviewed and presented in tabular form. This dictated that there are still research gaps in the field of blockchain-based cloud computing systems. This study proposed a model for secured data storage over a decentralized cloud by blockchain Ethereum.
The audit log is a crucial component to monitor fine-grained operations over sensitive data (e.g., personal, health) for security inspection and assurance. Since such data operations can be highly sensitive, it is vital to ensure that the audit log achieves not only validity and immutability, but also confidentiality against active threats to standard data regulations (e.g., HIPAA) compliance. Despite its critical needs, state-of-the-art privacy-preserving audit log schemes (e.g., Ghostor (NSDI '20), Calypso (VLDB '19)) do not fully obtain a high level of privacy, integrity, and immutability simultaneously, in which certain information (e.g., user identities) is still leaked in the log. In this paper, we propose Harpocrates, a new privacy-preserving and immutable audit log scheme. Harpocrates permits data store, share, and access operations to be recorded in the audit log without leaking sensitive information (e.g., data identifier, user identity), while permitting the validity of data operations to be publicly verifiable. Harpocrates makes use of blockchain techniques to achieve immutability and avoid a single point of failure, while cryptographic zero-knowledge proofs are harnessed for confidentiality and public verifiability. We analyze the security of our proposed technique and prove that it achieves non-malleability and indistinguishability. We fully implemented Harpocrates and evaluated its performance on a real blockchain system (i.e., Hyperledger Fabric) deployed on a commodity platform (i.e., Amazon EC2). Experimental results demonstrated that Harpocrates is highly scalable and achieves practical performance.
We present a forward-secure public-key encryption (PKE) scheme without key update, i.e. both public and private keys are immutable. In contrast, prior forward-secure PKE schemes achieve forward security by constantly updating the secret keys. Our scheme is based on witness encryption by Garg et al. (STOC 2013) and a proof-of-stake blockchain with the distinguishable forking property introduced by Goyal et al. (TCC 2017), and ensures a ciphertext cannot be decrypted more than once, thereby rendering a compromised secret key useless with respect to decryption of past ciphertext the legitimate user has already decrypted. In this work, we formalize the notion of blockchain-based forward-secure PKE, show the feasibility of constructing a forward-secure PKE scheme without key update, and discuss interesting properties of our scheme such as post-compromise security.
Nakamoto proof-of-work ledger consensus currently underlies the majority of deployed cryptocurrencies and smart-contract blockchains. While a long and fruitful line of work has succeeded to identify its exact security region---that is, the set of parametrizations under which it possesses asymptotic security---the existing theory does not provide concrete settlement time guarantees that are tight enough to inform practice.
Tim Ruffing, Viktoria Ronge, Elliott Jin, Jonas Schneider-Bensch · 5 authors
Bitcoin and other cryptocurrencies have recently introduced support for Schnorr signatures whose cleaner algebraic structure, as compared to ECDSA, allows for simpler and more practical constructions of highly demanded ''t-of-n'' threshold signatures. However, existing Schnorr threshold signature schemes still fall short of the needs of real-world applications due to their assumption that the network is synchronous and due to their lack of robustness, i.e., the guarantee that t honest signers are able to obtain a valid signature even in the presence of other malicious signers who try to disrupt the protocol. This hinders the adoption of threshold signatures in the cryptocurrency ecosystem, e.g., in second-layer protocols built on top of cryptocurrencies.
Carsten Baum, Robin Jadoul, Emmanuela Orsini, Peter Schöll · 5 authors
Zero-Knowledge protocols have increasingly become both popular and practical in recent years due to their applicability in many areas such as blockchain systems. Unfortunately, public verifiability and small proof sizes of zero-knowledge protocols currently come at the price of strong assumptions, large prover time, or both, when considering statements with millions of gates. In this regime, the most prover-efficient protocols are in the designated verifier setting, where proofs are only valid to a single party that must keep a secret state.
Tim Güneysu, Philip Hodges, Georg Land, Mike Ounsworth · 6 authors
Certificate authorities in public key infrastructures typically require entities to prove possession of the secret key corresponding to the public key they want certified. While this is straightforward for digital signature schemes, the most efficient solution for public key encryption and key encapsulation mechanisms (KEMs) requires an interactive challenge-response protocol, requiring a departure from current issuance processes. In this work we investigate how to non-interactively prove possession of a KEM secret key, specifically for lattice-based KEMs, motivated by the recently proposed KEMTLS protocol which replaces signature-based authentication in TLS 1.3 with KEM-based authentication. Although there are various zero-knowledge (ZK) techniques that can be used to prove possession of a lattice key, they yield large proofs or are inefficient to generate. We propose a technique called verifiable generation, in which a proof of possession is generated at the same time as the key itself is generated. Our technique is inspired by the Picnic signature scheme and uses the multi-party-computation-in-the-head (MPCitH) paradigm; this similarity to a signature scheme allows us to bind attribute data to the proof of possession, as required by certificate issuance protocols. We show how to instantiate this approach for two lattice-based KEMs in Round 3 of the NIST post-quantum cryptography standardization project, Kyber and FrodoKEM, and achieve reasonable proof sizes and performance. Our proofs of possession are faster and an order of magnitude smaller than the previous best MPCitH technique for knowledge of a lattice key, and in size-optimized cases can be comparable to even state-of-the-art direct lattice-based ZK proofs for Kyber. Our approach relies on a new result showing the uniqueness of Kyber and FrodoKEM secret keys, even if the requirement that all secret key components are small is partially relaxed, which may be of independent interest for improving efficiency of zero-knowledge proofs for other lattice-based statements.
Lorenzo Grassi, Dmitry Khovratovich, Reinhard Lüftenegger, Christian Rechberger · 6 authors
We propose a new hash function Reinforced Concrete, which is the first generic purpose hash that is fast both for a zero-knowledge prover and in native x86 computations. It is suitable for a various range of zero-knowledge proofs and protocols, from set membership to generic purpose verifiable computation. Being up to 15x faster than its predecessor Poseidon hash, Reinforced Concrete inherits security from traditional time-tested schemes such as AES, whereas taking the zero-knowledge performance from a novel and efficient decomposition of a prime field into compact buckets.
We study the problem of constructing succinct zero knowledge proof systems for floating point computations. The standard approach to handle floating point computations requires conversion to binary circuits, following the IEEE-754 floating point standard. This approach incurs a poly(w) overhead in prover efficiency for computations with w-bit precision, resulting in very high prover runtimes -- already the key bottleneck in the design of succinct arguments. We make the following contributions: -We propose a new model for verifying floating point computations that guarantees approximate correctness w.r.t. a relative error bound. This model is inspired by numerical analysis, and is very meaningful for applications such as machine learning and scientific computing. -Using this model, we present a general method for constructing succinct zero-knowledge proofs for floating point computations starting from existing public-coin "commit-and-prove'' systems. For computations with w-bit precision, our approach incurs only a log(w) overhead in prover running time. Our compiler nearly preserves (up to a factor of 2) the communication complexity of the underlying protocol, and requires sub-linear verification time. The resulting proof can be made non-interactive in the random oracle model. Concretely, our scheme is ~57x faster than the method following IEEE standard exactly [35] for 32-bit floating point computations. Central to our main result, and of independent interest, is a new batch range proof system in standard prime order groups that does not rely on bit decomposition.
Ning Luo, Timos Antonopoulos, William R. Harris, Ružica Piskač · 6 authors
Zero-knowledge (ZK) protocols enable one party to prove to others that it knows a fact without revealing any information about the evidence for such knowledge. There exist ZK protocols for all problems in NP, and recent works developed highly efficient protocols for proving knowledge of satisfying assignments to Boolean formulas, circuits and other NP formalisms. This work shows an efficient protocol for the converse: proving formula unsatisfiability in ZK (when the prover posses a non-ZK proof). An immediate practical application is efficiently proving safety of secret programs.
Decentralised Autonomous Organisations (DAOs) have the capability of being a disruptive Web3 technology. Their usage of cryptographically secure distributed ledgers shows promise of replacing existing technical and financial intermediaries. However, this promise has not been fully materialised yet: existing attempts typically rely on centralisation as the required decentralised components do not exist or are not mature enough. We present our Web3 Deployment Experiment around a robust decentralised economy to address these issues. Our economy is unique due to the removal of all centralised components and governance. It is resilient against legal and economic attacks as no individual or organisation can compromise its functioning. We dub this characteristic extreme decentralisation. Similar to BitTorrent and Bitcoin, our extreme decentralisation DAOs carefully avoid single points of failure and are effectively unstoppable. Within our experiment around a music economy, we bypass all intermediaries in finance, technology, and the music industry itself with a direct donation to musicians. We demonstrate the viability of collective decision-making within our decentralised economy and present a set of principles for Web3 DAOs. Our implementation shows that the DAO ecosystem is fully deployable on smartphones, allowing anyone to create a DAO without reliance on central authorities or components.
Cryptocurrencies have the potential to enable socioeconomic growth throughout the world by offering easier access to capital and financial services. However, many virtual asset service providers (VASPs) that offer cryptocurrency services lack identity management and can be accessed anonymously, which has led to their services being exploited by criminal activities such as money laundering and illegal foreign exchange. Such crimes have a negative impact on socioeconomic sustainability. Building identity systems on blockchains can help VASPs improve their identity management to combat cryptocurrency-based crimes so VASPs can better serve the social economy and achieve their sustainability goals. However, existing solutions have privacy problems because the identity provider can associate users’ identities with their wallet accounts. In addition, there is currently no solution that can support all public blockchains unconditionally, as current solutions can only support EVM-compliant blockchains or require additional work to support new blockchains. This article proposes a KYC (know your customer)-compliant identity scheme based on Ethereum using Merkle trees and smart contracts. The identity and wallet accounts are linked by the user rather than the KYC provider so, in general, no one but the user knows the association between the wallet accounts and the identity, which protects privacy. For suspicious accounts, supervisors can trace their identities and thus achieve supervision. In addition, the scheme supports identifying accounts on all public blockchains by using Merkle trees and smart contracts to bind accounts on multiple blockchains to one identity and no extra work is required. Moreover, the scheme supports users to prove that their attributes meet the requirements of VASPs by adopting the BBS+ signature and the Sigma protocol.
Yukun Niu, Lingbo Wei, Chi Zhang, Jianqing Liu · 5 authors
Anonymous yet accountable authentication can protect users' privacy and security and prevent users from misbehaving when they access public Wi-Fi hotspots. However, most existing privacy-enhanced authentication schemes either do not meet the accountability requirements in public Wi-Fi hotspot access or they are inherently dependent on trusted third parties, and therefore are undeployable in practical settings. In this paper, we design and implement an access authentication scheme to simultaneously and efficiently provide anonymity and accountability without relying on any trusted third party by utilizing a permissionless blockchain (e.g., Bitcoin or Ethereum) and Intel SGX. Inspired by the recent progress on Bitcoin techniques such as Colored Coins, we utilize the unmodified Bitcoin blockchain as the powerful platform to manage access credentials without introducing any trusted third party. We leverage SGX-based mixer to allow users to anonymously exchange their access credentials and design the verification path of access credentials to support blacklisting misbehaving access credentials without compromising users' anonymity. By integrating with the anti-double-spending property of the Bitcoin blockchain, our scheme can simultaneously provide users' accountability and anonymity without involving any trusted third party. Finally, we demonstrate that our proposed scheme is compatible with the current Bitcoin system or other permissionless blockchains, and is highly effective and practical for public Wi-Fi hotspot access control systems.
Mohamed A. El-Zawawy, Alessandro Brighente, Mauro Conti
The inclusion of drones in Internet of Vehicles (IoV) is a current trend that presents significant trade-offs. On the one hand, Unmanned Aerial Vehicles (UAVs) provide advantages such as enabling ground communications also when physical obstacles limit the connectivity. On the other hand, they increase the attack surface. For instance, physical attacks on drones provide the attacker with credentials that can be used to inject bogus information into the IoV network, thus jeopardizing not only security but also users’ safety. In this scenario, authentication plays a fundamental role to guarantee security. It is however fundamental to develop authentication protocols that can, at the same time, protect ground users’ data and prevent attacks to drones. However, currently available authentication schemes cannot guarantee security in case of attacks to drones. In this paper, we propose a Blockchain-supported authentication protocol for Drone-assisted IoV using Elliptic curve cryptography (BDIVE). Compared to existing authentication protocols, we extend the threat model from an honest-but-curious drone to active attacks against drones.BDIVEprovides both energy-efficiency, traceability, and accountability thanks to the use of blockchain at the Trusted Authority (TA). Using Burrow-Abadi–Needham (BAN) logic, we analyze and prove the security of mutual authentication inBDIVE. We also prove the security ofBDIVEagainst several attacks by implementing it in AVISPA. To assess its scalability and energy efficiency, we implementBDIVEusing Omnetpp with its Castalia simulator. The comparison ofBDIVEwith currently existing authentication protocols, shows that it reduces the energy consumption up to 70% and the computational cost up to 68%, while providing resistance to previously unconsidered attack vectors.
The assignment problem is an essential problem in many application fields and frequently used to optimize resource usage. The problem is well understood and various efficient algorithms exist to solve the problem. However, it was unclear what practical performance could be achieved for privacy-preserving implementations based on multiparty computation (MPC) by leveraging more efficient solution strategies than MPC-based generic simplex solvers for linear programs. We solve this question by implementing and comparing different optimized MPC algorithms to solve the assignment problem for reasonable problem sizes. Our empirical approach revealed various insights to MPC-based optimization and we measured a significant (50x) speed-up compared to the known simplex-based approach. Furthermore, we also study the overhead introduced by making the results publicly verifiable by means of non-interactive zero-knowledge proofs. By leveraging modern proof systems we also achieve significant speed-up for proof and verification times compared to the previously proposed approaches as well as compact proof sizes. Our research was motivated by a real-world use case, based on detailed discussions with representative stakeholders from the aviation industry.
Suhair Alshehri, Omaimah Bamasaq, Daniyal Alghazzawi, Arwa A. Jamjoom
The Internet of Things (IoT) is vulnerable to leakage of private information during data sharing. To avoid this problem, access control and secure data sharing have been introduced in IoT; however, many challenges are faced because of centralized access control and single delegator selection. Additionally, blockchain is integrated into IoT to enhance the security of the environment. For that purpose, this research proposes dynamic secure access control using the blockchain (DSA-Block) model, which performs secure access control and data sharing. Initially, the IoT device attributes and user attributes are registered at a local domain authority (LDA) for generating private and public keys using the hyperelliptic curve cryptography (HECC) algorithm, which ensures the legitimacy of the users and devices. Then, the IoT devices send a request message to the edge nodes (ENs) via a gateway, which performs request filtration by validating the user’s authenticity. The filtered requests are sent to the edge server to perform access delegation using rock hyraxes swarm optimization (RHSO), which selects a set of delegator nodes. The access control decision is made by using the Trusted practical Byzantine fault tolerance (PBFT) consensus algorithm. The IoT data are stored in the cloud server for secure storage, in which the data are secured using a differential privacy mechanism. Finally, dual revocations, such as user attribute revocation and user revocation, are used to maintain security. The performance of DSA-Block is evaluated and the results demonstrate that the proposed DSA-Block model achieves superior performance compared to previous works.
Most blockchains are designed to be immutable such that an object, e.g., a block or a transaction, is persisted once it has been registered. However, blockchain immutability hinders blockchain development due to the increasing abuse of blockchain storage and legal obligations. To break immutability in a controlled way, Derler et al. (NDSS’19) proposed a redactable blockchain with fine-grained controllable rewriting by introducing the notion of policy-based chameleon hash (PCH). Given a PCH-based object associated with an access policy, a trapdoor holder whose rewriting privileges satisfy the access policy can alter the object. Although this work offers an elegant approach to blockchain rewriting, it lacks accountability. In practice, the trapdoor holders may abuse their rewriting privileges, and even use their chameleon trapdoor to build a device in a blackbox manner to gain illegal profits while avoiding being caught. In this paper, we introduce a new design of PCH with blackbox accountability (PCHA). Blackbox accountability offers not only linkability between any modified object and its modifier, but also traceability that enables a central authority to identify responsible trapdoor holders whose secret keys have contributed to the blackbox device. Besides modeling PCHAs, we present a generic construction of PCHAs with rigorous security proofs. We instantiate a concrete construction of PCHA by introducing a practical attribute-based traitor tracing (ABTT) with adaptive security on prime-order pairing groups. The experimental analysis demonstrates that our PCHA and ABTT schemes have modest overheads and superior functionality to the state-of-the-art solutions. In particular, the price of accountability in key generation, hash, and adaption is almost negligible compared to the state-of-the-art solution.
With the development of the Internet of Things (IoT) and its applications, a large amount of data is generated regularly. If this information is used by malicious attackers, it will be a great disaster for the relevant users. In this regard, this article focuses on the user’s identity privacy issues involved in the IoT. By protecting the user’s identity privacy, the attacker cannot associate the obtained data with the user’s real identity, and so achieve the purpose of protecting the user. This article uses the features of blockchain that cannot be tampered with nor forged to strengthen the reliability of the system. The proposed scheme saves the transaction information of user information through the Hyperledger and uses the ring signature method to obscure the real identity. A key generator is used to generate system public parameters and ring membership information required for signature. Users can use this information to hide their identity in a ring group of n users so that other users can only guess the true identity of the user with a probability of 1/n. Additionally, the method of aggregated signature is used to shorten the time and space required for k signature verification to 1/k, which greatly improves the efficiency. Finally, this article also uses an accountability mechanism to punish some attackers who attempt to waste system resources by revealing the real identity of the attacker and refusing to serve him. In this paper, GO language is used to write chain code to realize the proposed algorithm, and a prototype system is built through HyperLeger Fabric blockchain network, and the prototype system is verified by experiment. The correctness and efficiency of the above scheme are also proved through theoretical analysis and experiments.
Blockchain systems based on a reusable resource, such as proof-of-stake (PoS), provide weaker security guarantees than those based on proof-of-work. Specifically, they are vulnerable to long-range attacks, where an adversary can corrupt prior participants in order to rewrite the full history of the chain. To prevent this attack on a PoS chain, we propose a protocol that checkpoints the state of the PoS chain to a proof-of-work blockchain such as Bitcoin. Our checkpointing protocol hence does not rely on any central authority. Our work uses Schnorr signatures and leverages Bitcoin recent Taproot upgrade, allowing us to create a checkpointing transaction of constant size. We argue for the security of our protocol and present an open-source implementation that was tested on the Bitcoin testnet.