Fair Exchange Protocol Research Articles

Achieving autonomous fair exchange in ubiquitous network settings

This paper addresses the issue of fair (signature or key) exchange in emerging ubiquitous commerce (u-commerce). Such an application poses new security challenges. In particular, it involves distributed and autonomous operations running in a much open, dynamic and resource-diversified networking environment, which makes an exchange highly susceptible to security attacks and system failures. Existing approaches to fair exchange are ineffective in dealing with the new challenges as their design did not envisage such complex operational situations. In this paper, we aim to propose a novel fair exchange protocol specifically for u-commerce in response to the new challenges. The protocol is supported by an integration of several techniques, such as threshold proxy signatures, purpose-restricted encryption key certification and threshold verifiable proxy encryption, to accomplish the fairness of exchange in u-commerce settings. The protocol analysis is also provided for the proof of its fairness.

State and Progress in Strand Spaces: Proving Fair Exchange

Many cryptographic protocols are intended to coordinate state changes among principals. Exchange protocols, for instance, coordinate delivery of new values to the participants, i.e. additions to the set of values they possess. An exchange protocol is fair if it ensures that delivery of new values is balanced: If one participant obtains a new possession via the protocol, then all other participants will, too. Understanding this balanced coordination of different principals in a distributed system requires relating (long-term) state to (short-term) protocol activities. Fair exchange also requires progress assumptions. In this paper we adapt the strand space framework to protocols, such as fair exchange, that coordinate state changes. We regard the state as a multiset of facts, and we allow protocol actions to cause local changes in this state via multiset rewriting. Second, progress assumptions stipulate that some channels are resilient--and guaranteed to deliver messages--and some principals will not stop at critical steps. Our proofs of correctness cleanly separate protocol properties, such as authentication and confidentiality, from properties about progress and state evolution. G. Wang's recent fair exchange protocol illustrates the approach.

Fair exchange protocol of Schnorr signatures with semi-trusted adjudicator

In this paper, we propose an optimistic fair exchange protocol of Schnorr signatures with a semi-trusted adjudicator. In this protocol, we enforce the adjudicator accountability in the protocol to relax excessive reliance on the trust of the adjudicator, so that the adjudicator only needs to be trusted by the signer. We present a security model and then show that the protocol is strong EUF–CMA secure under the standard Discrete Logarithm (DL) assumption in the random oracle model. Finally, we compare the performance of the fair exchange protocol of Schnorr signatures.

Decentralized fair multi-party exchange protocol under P2P environment

The multi-party exchange of valuable digital resources in P2P environment has some problem on resources certification and objects exchange.A decentralized fair multi-party exchange protocol was proposed.The protocol adopted cross-validation theory to identify recourses and solved the problem of the negotiation among multi-party exchanges in term of one-way release mechanism and the new one-way exchange mesh structure.Meanwhile,the protocol certificated its own fairness on the basis of right cross validation.

Fair Exchange in Strand Spaces

Many cryptographic protocols are intended to coordinate state changes among principals. Exchange protocols coordinate delivery of new values to the participants, e.g. additions to the set of values they possess. An exchange protocol is fair if it ensures that delivery of new values is balanced: If one participant obtains a new possession via the protocol, then all other participants will, too. Fair exchange requires progress assumptions, unlike some other protocol properties. The strand space model is a framework for design and verification of cryptographic protocols. A strand is a local behavior of a single principal in a single session of a protocol. A bundle is a partially ordered global execution built from protocol strands and adversary activities. The strand space model needs two additions for fair exchange protocols. First, we regard the state as a multiset of facts, and we allow strands to cause changes in this state via multiset rewriting. Second, progress assumptions stipulate that some channels are resilient-and guaranteed to deliver messages-and some principals are assumed not to stop at certain critical steps. This method leads to proofs of correctness that cleanly separate protocol properties, such as authentication and confidentiality, from invariants governing state evolution. G. Wang's recent fair exchange protocol illustrates the approach.

Fair Electronic Exchange Based on Fingerprint Biometrics

Fair exchange between two parties can be defined as an instance of exchange such that either both parties obtain what they expected or neither one does. Protocols that facilitate such transactions are known as “fair exchange protocols”. We analyze one such protocol by Micali that demonstrates fair contract signing, where two parties exchange their commitments over an already negotiated contract. In this journal we show that Micali’s protocol is not completely fair and demonstrate the possibilities for one party cheating by obtaining the other party’s commitment and not offer theirs. A revised version of this protocol by Bao provides superior fairness by handling the above mentioned weakness but fails to handle the possibility of a replay attack. Our proposed protocol improves upon Bao’s protocol by addressing the weakness that leads to a replay attack. We also demonstrate a software implementation of our system which provides fair contract signing along with properties like user authentication achieved through the use of a fingerprint based authentication system and features like confidentiality, data-integrity and non-repudiation through implementation of hybrid cryptography and digital signatures algorithms based on Elliptic Curve Cryptography.

Identity-based fair multi-party exchange protocol

Because of multiple parties,efficiency of multi-party exchange protocol is very important.An Identity-based verifiably encrypted signature scheme using bilinear pairings on ellipse curve was constructed,and a new fair multi-party exchange protocol was designed.The proposed protocol provides high efficiency,shorter length of signature,and meets the demands of fairness,timeliness,validity,optimality.It has important theoretical and application value.

LTL model checking for security protocols

Most model checking techniques for security protocols make a number of simplifying assumptions on the protocol and/or on its execution environment that greatly complicate or even prevent their applicability in some important cases. For instance, most techniques assume that communication between honest principals is controlled by a Dolev-Yao intruder, i.e. a malicious agent capable to overhear, divert, and fake messages. Yet we might be interested in establishing the security of a protocol that relies on a less unsecure channel (e.g. a confidential channel provided by some other protocol sitting lower in the protocol stack). In this paper we propose a general model for security protocols based on the set-rewriting formalism that, coupled with the use of LTL, allows for the specification of assumptions on principals and communication channels as well as of complex security properties that are normally not handled by state-of-the-art security protocol analysers. By using our approach we have been able to formalise all the assumptions required by the ASW protocol for optimistic fair exchange and some of its key security properties. Besides the previously reported attacks on the protocol, we report a new attack on a patched version of the protocol.

A generalised model of e-trading for gradual secret release fair exchange protocol

In this article, we propose a generalised model of e-trading for the development of gradual secret release fair exchange protocols. Based on the model, the methodology is narrated to implement e-trading protocols that ensure fairness in true sense without using an additional trusted third party for which either party has to pay. The model provides the scope to include the correctness of the product, money atomicity and customer's anonymity properties within e-trading protocol. We conclude this article by indicating the area of applicability for the proposed model.

Probabilistic Analysis and Verification of the ASW Protocol Using PRISM

The ASW protocol is one of the prominent optimistic fair exchange protocols that is used for contract signing between two participants, the originator and the responder, with the aid of a trusted third party in case of a dispute. In this paper, the key security objectives of ASW protocol-fairness, effectiveness and timeliness-have been verified using a probabilistic model checking tool, PRISM. First, the security objectives of ASW protocol have been defined with probabilistic equations. The roles of the participants (i.e., the originator and the responder) and the trusted third party have been modeled in PRISM code. The security objectives of ASW protocol have been expressed using a temporal logic, PCTL. The PCTL expressions are analogous to the probabilistic equations that we have developed to define the security objectives. Next, the model is analyzed using these PCTL expressions, and different outputs have been observed. The outputs confirm the fairness of the ASW protocol. Moreover, the effectiveness and the timeliness of the protocol are also established. Hence, the key security properties of ASW protocol have been verified.

Certificate-based fair exchange protocol of signatures from pairings

In 2003, Boneh et al. proposed the first non-interactive verifiably encrypted signature scheme that can be used to construct optimistic fair exchange protocols of signatures. However, their scheme depends on an entirely honest adjudicator, neither forging signatures nor colluding with one party. To eliminate this unrealistic premise, we propose a new paradigm for building fair exchange protocols of signatures from pairings by choosing a certificate authority CA as an adjudicator. In this paradigm, a certificate, or generally, a signature plays threefold role, firstly acts as the binding of the public key and its holder, secondly acts as a decryption key, and thirdly acts as CA's guarantee against partiality in adjudication. The proposed protocol not only overcomes the classical authentication problem of public keys, but also relaxes excessive reliance on the trustworthiness of the adjudicator so that the adjudicator only needs to be trusted by the signer.

An optimistic fair exchange protocol based on signature policies

The growth of the e-commerce has allowed companies and individuals to sell and purchase almost any kind of product and service through the Internet. However, during the purchase transaction there is a moment during which the seller has sensitive information from the buyer, typically his/her credit card information, while the buyer has nothing from the seller. This situation clearly places the buyer at disadvantage and is, together with fear of fraud, one of the reasons of the lack of confidence in e-commerce. For resolving this situation a new fair exchange protocol based on signature policies is presented. A signature policy is a set of rules to create and validate electronic signatures, under which an electronic signature can be determined to be valid in a particular transaction context. Due to the signature policy-based design, the proposed protocol allows the buyer to decide if trust or not in the rules that will manage the transaction, increasing the user's confidence in e-commerce. Security, fairness and timeliness characteristics of the protocol are evaluated. Implementation guidelines are also provided taking into consideration latest security standards.

Certificate-based verifiably encrypted signatures from pairings

We propose a new verifiably encrypted signature scheme from pairings by choosing a certificate authority (CA) as an adjudicator. In this scheme, a certificate, or generally, a signature acts not only as the binding of the public key and its holder, but also as CA’s guarantee against partiality in adjudication. Under the CDH assumption and in the random oracle model, we show that the new scheme is EUF-CMA secure in a stronger security model. In this security model, there are three types of inside adversaries with more power than those in previous verifiably encrypted signature schemes. The proposed scheme can solve the authentication problem of public keys and relax excessive reliance on the trustworthiness of the adjudicator so that the adjudicator only needs to be trusted by the signer. Hence, the fair exchange protocols of signatures based on the new scheme is more trustworthy and practical than the previous ones.

An optimistic fair exchange protocol and its security in the universal composability framework

Fair exchange protocols allow both or neither of two parties to obtain the other's items, and this property is essential in e-commerce. In this paper, we construct an optimistic fair exchange protocol that is applicable to any digital signature by prescribing three forms of signatures, namely presignature, post-signature and notarised signature. We set an expiration date for presignature, and thus realise the timely termination of the protocol. Next, we define an ideal functionality of fair exchange protocols in the universal composability framework. Then, we construct an optimistic fair exchange protocol based on the above protocol, and prove its security in the universal composability framework.

An e-commerce fair exchange protocol that enforces the customer to be honest

A new optimistic fair exchange protocol between a Customer (C) and a Merchant (M) is presented, that makes minimum use of a Trusted Third Party. The protocol is for exchanging a payment with a digital product in the B2C domain. A novel feature of the protocol is that once the parties have agreed to the exchange, then one party is encouraged to be honest whereas the other party is forced to be honest. The protocol has the following features: (1) it comprises of only three messages sent between C and M in the exchange phase; (2) it guarantees strong fairness for both C and M; (3) it allows both parties to be sure of the item that they will receive and (4) it automatically resolves disputes online.

Fair exchange protocol of signatures based on aggregate signatures

In Eurocrypt 2003, Boneh et al. proposed verifiably encrypted signatures from the concept of aggregate signatures that support aggregation. Such signatures enable verifiers to test that a given ciphertext is the encryption of a signature on a given message. Verifiably encrypted signatures are used in fair exchange protocols of signatures. In this paper, we first show that Boneh et al.’s verifiably encrypted signature is not secure against rogue-key attacks. Moreover, the fairness of fair exchange protocols of signatures with the adjudicator relies on the neutrality of the adjudicator, which has become a major practical hindrance to fair exchange protocols of signatures getting widely deployed. Then we propose a fair exchange protocol of signatures from pairings by using aggregate signatures. We not only enhance the fair exchange protocol of signatures against three types of inside attackers but also relax the need of the trust in the adjudicator so that it only needs to be trusted by the signer.

A methodology for verification of digital items in fair exchange protocols with active trustee

Fair exchange constitutes a fundamental mechanism for electronic commerce. Fair exchange assumes that it is possible to verify the correctness of the digital items to be exchanged. However, when an...

Experiences in developing a fair-exchange e-commerce protocol using common off-the-shelf components

Fair-exchange is an important property that must be ensured in all electronic commerce environments where the merchants and the customers are reluctant to trust each other. This property guarantees that none of the transacting parties suffer because of the fraudulent behavior of the other party in the transaction. In this paper, we describe our experiences in developing a new e-commerce protocol to address the problem of fair-exchange for digital products. The protocol is based on a novel cryptographic technique that we had proposed earlier. We show how to use common off-the-shelf software components to develop such a protocol.

Constructing Optimistic ID-Based Fair Exchange Protocols via Proxy Signature

This paper introduces a natural paradigm for fair exchange protocols, called ID-based partial proxy signature scheme. A security model with precise and formal definitions is presented, and an efficient and provably secure partial proxy signature scheme is proposed. This is a full ID-based optimistic fair exchange protocol. Unlike the vast majority of previously proposed protocols, this approach does not use any zero knowledge proofs, and thus avoids most of the costly computations.

Exclusions and related trust relationships in multi-party fair exchange protocols

Some electronic commerce transactions are inherently performed between more than two parties. In this context, it is thus important to determine whether the underlying fair exchange protocols allowing the secure implementation of such transactions enable participants to exclude other entities from a protocol execution. This is an important point that has not been sufficiently addressed when analysing such kind of protocols, and that may be crucial for the successful accomplishment of multi-party electronic transactions. In this paper we define the properties related to exchange protocols and exclusions, study exclusion scenarios on two well-known multi-party fair exchange protocols and point out the implications that exclusions may have on the trust relationships between participants, and, more generally, on electronic commerce. Two new protocols more robust than existing multi-party fair exchange protocols are therefore proposed.