Fair Exchange Protocol Research Articles

Secure decentralized firmware update delivery service for Internet of Things

With the increasing number of Internet of Things devices, it is crucial to keep them up-to-date to prevent cyber attacks. Traditional centralized delivery is not suitable for scaling and also can be too expensive to run for small vendors. Thus, finding a fully secure, scalable, yet cost-efficient firmware update distribution strategy is always an open research problem. This paper tries to answer those problems by proposing Patchman, a secure decentralized firmware update delivery service for the Internet of Things ecosystem leveraging blockchain. When a new firmware patch is available, vendors make a bid in the smart contract for anyone to join as firmware distributors. For each successful delivery to targeted devices, distributors are rewarded with tokens. Meanwhile, devices gain a reputation score every time they successfully install an update. To ensure robustness and fairness, we develop secure fair exchange protocols using verifiable proof-of-delivery and proof-of-installation. Those proofs can be traded in the blockchain for rewards and reputation scores increase, proving that the proof-holders have successfully processed a firmware delivery and firmware installation task. This way, the firmware update delivery can be executed safely without centralized third-party control. Our evaluation results show that our implementation complies with the five security goals that we envision. We also have successfully punished malicious actions by confiscating their deposits and requiring them to pay up to four times of base deposit value when they join the next update task, ensuring the fairness of our protocol. Furthermore, we generate low processing delay overhead compared to existing works that rely on Zero-Knowledge Proofs. The gas usage consumption from our approach also produced a competitive result despite our works supporting more features than existing works, ensuring the efficiency of our proposal.

A Formal Model for Analyzing Fair Exchange Protocols Based on Event Logic

A Formal Model for Analyzing Fair Exchange Protocols Based on Event Logic

Quantum multi-party fair exchange protocol based on three-particle GHZ states

Quantum multi-party fair exchange protocol based on three-particle GHZ states

A Publicly Verifiable Optimistic Fair Exchange Protocol Using Decentralized CP-ABE

Abstract Fair exchange is a challenging problem for two mutually distrusting players. It is widely known that fair exchange is impossible without a trusted third party (TTP). However, relying on a single TTP can cause a single-point failure. An intuitive idea is to adopt multiple TTPs to distribute trust. This paper constructs a two-party optimistic fair exchange (OFE) protocol using decentralized ciphertext-policy attribute-based encryption (CP-ABE), achieving decentralized TTPs. This is achievable because decentralized CP-ABE ciphertext supports a nested access control policy. A nested access control policy fits perfectly in a fair exchange protocol which contains multiple roles (i.e. players and TTPs). Further, we apply non-interactive zero knowledge proofs to prove the well-formedness of ciphertexts, so as to enforce players to follow the protocol specification honestly. Consequently, we construct an OFE protocol in which each player’s operations are publicly verifiable without revealing secret information. Also, we obtain decentralized TTPs with optimism (i.e. the TTPs are involved only when arbitration is required), autonomy (i.e. the TTPs do not need to interact with each other), statelessness (i.e. the TTPs do not need to store data for the exchange protocol) and verifiability (i.e. the TTPs are publicly verifiable). Compared with previous work, our protocol assumes only a public communication channel and each party’s operations are publicly verifiable. Besides, it achieves a favorable $O(n)$ verification complexity in the normal case, where $n$ is the number of TTPs. Finally, we present a proof-of-concept implementation to demonstrate the feasibility.

A blockchain-based signature exchange protocol for metaverse

Electronic Commodity Trading has a pivotal role in our economic activities. In the literature, there is a classic problem called “Fair Exchange” which is fundamental to electronic commodity trading. It means the participants can receive the exchange item of the counterparty as they have agreed on before. Since the ownership of items online is often authorized by digital signatures, we focus on the problem of the fair exchange of digital signatures in this paper. As the concept of the Metaverse becomes popular recently, what we are concerned about is how the fair exchange will evolve in a metaverse. It is said that the metaverse is a vision of how the next generation of the internet will operate and the research for the fair exchange problem in it is essential for a wide range of applications like trading a (Non-fungible-token) NFT. Many cryptographic fair exchange protocols are proposed to deal with such a problem. However, most of them should rely on a Trusted Third Party (TTP) and the security is restricted by the TTP. The way the metaverse will work is still being defined. But it will probably provide users with a decentralized environment and a fair exchange protocol relying on a TTP seems unsuitable for it. Recently, researchers present some blockchain-based fair exchange protocols to get rid of or reduce the power of a TTP. But these blockchain-based protocols face new challenges. Firstly, cryptography pairing operations are often contained in such a TTP-free protocol and cost too much for the blockchain. Secondly, the player may hang for an unacceptably long time of the latency of the blockchain network. Thirdly, it is difficult to protect the privacy of the signatures while making the whole protocol verifiable at the same time. To bridge these research gaps, this paper presents a novel signature exchange protocol called DFSE which is decentralized, verifiable, efficient and autonomous. To give a real-world evaluation, we perform the experiment on the live test network of Ethereum and the results show that our protocol is feasible.

Formal Verification of Fair Exchange Based on Bitcoin Smart Contracts

Smart contracts are protocols that can automatically execute a transaction including an electronic contract when a condition is satisfied without a trusted third party. In a representative use-case, a smart contract is executed when multiple parties fairly trade on a blockchain asset. On blockchain systems, a smart contract can be regarded as a system participant, responding to the information received, receiving and storing values, and sending information and values outwards. Also, a smart contract can temporarily keep assets, and always perform operations in accordance with prior rules. Many cryptocurrencies have implemented smart contracts. At POST2018, Atzei et al. give formulations of seven fair exchange protocols using smart contract on Bitcoin: oracle, escrow, intermediated payment, timed commitment, micropayment channels, fair lotteries, and contingent payment. However, they only give an informal discussion on security.

Incentivizing Participation in Crowd-Sensing Applications Through Fair and Private Bitcoin Rewards

In this work we develop a rewarding framework that can be used to enhance existing crowd-sensing applications. Although a core requirement of such systems is user engagement, people may be reluctant to participate as sensitive information about them may be leaked or inferred from submitted data. The use of monetary rewards can help incentivize participation, thereby increasing not only the amount but also the quality of sensed data. Our framework allows users to submit data and obtain Bitcoin payments in a privacy-preserving manner, preventing curious providers from linking the data or the payments back to the user. At the same time, it prevents malicious user behavior such as double-redeeming attempts, where a user tries to obtain rewards for multiple submissions of the same data. More importantly, it ensures the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fairness</i> of the exchange in a completely trustless manner; by relying on the Blockchain, the trust placed on third parties in traditional fair exchange protocols is eliminated. Finally, our system is highly efficient as most of the protocol steps do not utilize the Blockchain network. When they do, only the simplest of Blockchain transactions are used as opposed to prior works that are based on the use of more complex smart contracts.

Optimally Efficient Multi-party Fair Exchange and Fair Secure Multi-party Computation

Multi-party fair exchange (MFE) and fair secure multi-party computation (fair SMPC) are under-studied fields of research, with practical importance. In particular, we consider MFE scenarios where at the end of the protocol, either every participant receives every other participant’s item, or no participant receives anything. We analyze the case where a trusted third party (TTP) is optimistically available, although we emphasize that the trust put on the TTP is only regarding the fairness , and our protocols preserve the privacy of the exchanged items against the TTP. In the fair SMPC case, we prove that a malicious TTP can only harm fairness, but not security . We construct an asymptotically optimal multi-party fair exchange protocol that requires a constant number of rounds (in comparison to linear) and O(n 2 ) messages (in comparison to cubic), where n is the number of participating parties. In our protocol, we enable the parties to efficiently exchange any item that can be efficiently put into a verifiable encryption (e.g., signatures on a contract). We show how to apply this protocol on top of any SMPC protocol to achieve fairness with very little overhead (independent of the circuit size). We then generalize our protocol to efficiently handle any exchange topology (participants exchange items with arbitrary other participants). Our protocol guarantees fairness in its strongest sense: even if all n-1 other participants are malicious and colluding with each other, the fairness is still guaranteed.

Privacy-preserving FairSwap: Fairness and privacy interplay

Abstract Fair exchange protocols are among the most important cryptographic primitives in electronic commerce. A basic fair exchange protocol requires that two parties who want to exchange their digital items either receive what they have been promised, or lose nothing. Privacy of fair exchange requires that no one else (other than the two parties) learns anything about the items. Fairness and privacy have been considered as two distinct properties of an exchange protocol. In this paper, we show that subtle ways of leaking the exchange item to the third parties affect fairness in fair exchange protocols when the item is confidential. Our focus is on Fair-Swap, a recently proposed fair exchange protocol that uses a smart contract for dispute resolution, has proven security in UC (Universal Composability) framework, and provides privacy when both parties are honest. We demonstrate, however, that FairSwap’s dispute resolution protocol leaks information to the public and this leakage provides opportunities for the dishonest parties to influence the protocol’s fairness guarantee. We then propose an efficient privacy-enhanced version of Fair-Swap, prove its security and give an implementation and performance evaluation of our proposed system. Our privacy enhancement uses circuit randomization, and we prove its security and privacy in an extension of universal composability model for non-monolithic adversaries that would be of independent interest.

Blockchain-Based Confidential Multiparty Contract Signing Protocol Without TTP Using Elliptic Curve Cryptography

Abstract Signed information is difficult to manage and this difficulty is even bigger when pieces of signed digital information have to be exchanged in an atomic procedure. Multiparty contract signing is an application of fair exchange of values, where the information to be exchanged are signed versions of a contract. Traditionally, this trust service requires the involvement of a trusted third party (TTP). This is a point of weakness for the generalization of the use of electronic contract signing protocols. Another usual problem for multiparty contract signing is that the protocols for multiparty exchanges are far more complex that those for two-party exchanges. Additionally, it is common that the signers demand protocols that assure the confidentiality of the contract. In this proposal blockchain-based technologies and smart contracts are used to obtain a protocol for electronic contract signing that does not need a TTP in any stage of the procedure. The protocol satisfies the ideal requirements for the contract signing service, even allowing the signature of confidential contracts. Moreover, the proposed solution is far more efficient than previous solutions for fair exchange protocols using blockchain presented up to the date thanks to the use of elliptic curve cryptography.

Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.

Blockchain-Based Fair and Secure Certified Electronic Mail Without a TTP

Certified mail is a special postal service that provides the sender with a proof that the mail was successfully received by the other party. However, when it comes to certified <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">electronic</i> mail (CEM), there has not been a widely accepted protocol yet. Most of the existing solutions rely on a Trusted Third Party (TTP) in order to achieve fairness, which can become a bottleneck and lead to more charges and computations. Other solutions that do not rely on a TTP have a relatively high computation and communication overhead. Blockchains have allowed the creation of TTP-free protocols for fair exchange; however, the existing Blockchain-based protocols are either too expensive or do not meet the necessary fairness and confidentiality guarantees. In this work, we have developed two TTP-free Blockchain-based protocols for certified electronic mail that achieve the required security properties of strong fairness, non-repudiation, timeliness, and confidentiality. The first protocol uses simple bitcoin transactions for a single receiver, whereas the second one implements smart contracts for one or multiple receivers. We have analyzed and compared both protocols to existing TTP-free Blockchain solutions and have demonstrated their superior properties and cost. Furthermore, we have implemented the two protocols in a realistic testbed, demonstrating the viability of our approach.

Efficient and Secure NFC Authentication for Mobile Payment Ensuring Fair Exchange Protocol

The standard protocol of near field communication (NFC) has concentrated primarily on the speed of communication while ignoring security properties. Message between an NFC-enabled smartphone and a point of sale are exchanged over the air (OTA), which is a message considered an authentication request for payment, billing, ticketing, loyalty services, identification or access control. An attacker who has an antenna can intercept or manipulate the exchanged messages to take advantage of these. In order to solve this problem, many researchers have suggested authentication methods for NFC communications. However, these remain inadequate transaction security and fairness. In this paper, we will propose a technique that ensures mutual authentication, security properties, and strong fairness. Mutual authentication is a security property that prevents replay attacks and man-in-the-middle attacks. Both fair exchange and transaction security are also significant issues in electronic transactions with regards to creating trust among the parties participating in the transaction. The suggested protocol deploys a secure offline session key generation technique to increase transaction security and, importantly, make our protocol lightweight while maintaining the fairness property. Our analysis suggests that our protocol is more effective than others regarding transaction security, fairness, and lightweight protocol. The proposed protocol checks robustness and soundness using Burrows, Abadi and Needham (BAN) logic, the Scyther tool, and automated validation of internet security protocols and applications (AVISPA) that provide formal proofs for security protocols. Furthermore, our protocol can resolve disputes in case one party misbehaves.

A Generic Framework for Accountable Optimistic Fair Exchange Protocol

Optimistic Fair Exchange protocol was designed for two parties to exchange in a fair way where an arbitrator always remains offline and will be referred only if any dispute happens. There are various optimistic fair exchange protocols with different security properties in the literature. Most of the optimistic fair exchange protocols satisfy resolution ambiguity where a signature signed by the signer is computational indistinguishable from the one resolved by the arbitrator. Huang et al. proposed the first generic framework for accountable optimistic fair exchange protocol in the random oracle model where it possesses resolution ambiguity and is able to reveal the actual signer when needed. Ganjavi et al. later proposed the first generic framework in the standard model. In this paper, we propose a new generic framework for accountable optimistic fair exchange protocol in the standard model using ordinary signature, convertible undeniable signature, and ring signature scheme as the underlying building blocks. We also provide an instantiation using our proposed generic framework to obtain an efficient pairing-based accountable optimistic fair exchange protocol with short signature.

Multi-party Fair Exchange Protocol with Smart Contract on Bitcoin

Traditional multi-party exchange protocols need a third party to ensure fairness. It can bring some communication costs and cryptanalytic attacks. In recent years, researchers have focused on blockchain to design a fair exchange protocol without a central authority. So far, there are a few works on fair exchange protocols for any topology based on bitcoin. This paper puts forward a decentralized protocol for star topology based on the bitcoin, that is, our protocol does not contain a third party. Communication costs, information disclosure, and cryptanalytic attacks are not considered for the third party. These features greatly reduce the burden and increase the efficiency of the protocol. To guarantee the fairness, a commitment scheme is provided. And the proposed protocol constructs an ideal function as a smart contract. The bitcoin is automatically transferred in the limited time instead of manual operations. Security analysis shows that our construction can guarantee fairness, resist double spending and sybil attack. Meanwhile, the proposed protocol enjoys high efficiency. Moreover, with a slight modification, our protocol can be extended to apply to any topology.

Toward Fairness of Cryptocurrency Payments

Motivated by the great success and adoption of Bitcoin, a number of cryptocurrencies such as Litecoin, Dogecoin, and Ethereum are becoming increasingly popular. Although existing blockchain-based cryptocurrency schemes can ensure reasonable security for transactions, they do not consider any notion of fairness. Fair exchange allows two players to exchange digital “items,” such as digital signatures, over insecure networks fairly, so that either each player gets the other’s item, or neither player does. Given that blockchain participants typically do not trust each other, enabling fairness in existing cryptocurrencies is an essential but insufficiently explored problem. In this article, we explore the solution space for enabling the fair exchange of a cryptocurrency payment for a receipt. We identify the timeliness of an exchange as an important property especially when one of the parties involved in the exchange is resource-constrained. We introduce the notion of strong timeliness for a fair exchange protocol and propose two fair payment-for-receipt protocol instantiations that leverage functionality of the blockchain to achieve strong timeliness. We implement both and compare their security and efficiency.

Cecoin: A decentralized PKI mitigating MitM attacks

For numerous applications, it is essential to reliably link a public key with its owner. The current solution is to employ the well-known Public Key Infrastructure (PKI), represented by a trusted certificate authority (CA), to fulfill this assignment by signing the certificate for the public key after validating its owner. However, due to the centralized architecture, it raises the single-point failure problem with unpredictable threats. In this paper, we present a distributed certificate scheme, referred to as Cecoin which is inspired by the well-known Bitcoin by employing its irreversible unforgeability and public verifiability. In Cecoin, the certificates can be treated as currencies and recorded on block chain, which removes the single point failure problem. The miners can verify the validity of certificates following a set of rules to ensure ownership consistency, and allow an identity to bind multiple public-key certificates. For efficient retrieval and verification of certificates, and quick operations, we incorporate the modified Merkle Patricia tree and employ it to implement a distributed Certificate Library. To allow the owner to transfer the possession of identity, we design an online fair exchange protocol without a trusted third party. Security and efficiency analyses show that our Cecoin provides strong security with desirable efficiency.

New Security Concurrent Signature Design

The rapid growth of the Internet has accelerated e-commerce application development. Numerous problems involving Internet trade transaction security remain. Therefore, security and transaction fairness establishment in e-commerce applications is a crucial research topic. A fair exchange protocol enables users to securely obtain information from each other. This has become a widely applied research topic in e-commerce. A concurrent signature eliminates the need for a trusted third party (TTP) or substantial mutual communication between two parties, to provide fair exchange protocol with e-commerce ideas. The concurrent signature concept was proposed by Chen et al. in 2004 EUROCRYPT. Some researchers improved the concurrent signature susceptibility to the message substitution attack defect, but there are still identify authentication and information exchange procedure security issues. This paper proposes a concurrent signature scheme based on elliptic curve cryptography (ECC) that uses the same security strength shorter key length, reduces public storage costs and the calculation and management risks. We strengthen the identity authentication mechanisms to prevent the counterfeiting identity attacks and provide a more confidential protocol through a self-certified mechanism.

Provably secure robust optimistic fair exchange of distributed signatures

We introduce the concept of optimistic fair exchange of distributed signatures (OFEDS) which allows two groups of parties to fairly exchange digital signatures. Specifically, an authorized set of parties from each group can jointly take part in the protocol on behalf of the affiliated group to fulfill obligation, and a semi-trusted arbitrator will intervene in the protocol only when there are disputes between two sides. Our OFEDS extends the functionality of optimistic fair exchange of threshold signatures to a more generic case. We formalize the security model of OFEDS, in which besides the standard security requirements for existing optimistic fair exchange protocols, robustness is incorporated so that OFEDS can be successfully performed even when there exist some dishonest signers. We propose a non-interactive construction of OFEDS based on the well-established Computational Diffie–Hellman (CDH) assumption. Our proposal shows that there exists CDH-based OFEDS for any general monotone access structure. Theoretical and experimental analyses demonstrate our OFEDS construction has reasonable efficiency for real applications.

An efficient resource-fair commit-prove-fair-open protocol

With the development of modern internet and mobile networks, there is an increasing need for privacy-preserving cooperative computation and cloud computing. Secure multi-party computation SMPC gives a general solution to these applications and has become a hot topic in privacy-carrying protocols. The commit-prove-fair-open protocol is one of multi-party fair exchange protocols against the malicious adversary in breaking the fair play of the participants, and it provides an important tool of SMPC to make it possible to achieve the fairness with corrupted majority according to the standard real/ideal world simulation paradigm framework. In this paper, we at first prove two lemmas about the simplified Camenisch-Shoup commitment and the time-lines, and then propose a very efficient resource-fair commit-prove-fair-open protocol. Compared with the other commit-prove-fair-open protocols, our new protocol enjoys two important advantages: 1 communications cost and computations price are less than 20%; 2 it allows commitment to obtain value 0, which is not implemented in the other constructions.