Fair multi-party contract signing using private contract signatures

Mukhamedov, Aybek; Ryan, Mark

doi:10.1016/j.ic.2007.07.007

Cited by 26 publications

(58 citation statements)

References 6 publications

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“…Because of its inefficiency, Baum-Waidner and Waidner [10] suggested a more efficient protocol, whose complexity depends on the number of dishonest parties, and if the number of dishonest parties is n − 1, its efficiency is the same as [27]. Mukhamedov and Ryan [44] decreased the round complexity to O(n). Lastly, Mauw et al [42] gave the lower bound of O(n 2 ) for the number of messages to achieve fairness.…”

Section: Related Workmentioning

confidence: 99%

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

Kılınç

Küpçü

2015

Lecture Notes in Computer Science

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Multi-party fair exchange (MFE) and fair secure multi-party computation (fair SMPC) are under-studied fields of research, with practical importance. We examine MFE scenarios where every participant has some item, and at the end of the protocol, either every participant receives every other participant's item, or no participant receives anything. This is a particularly hard scenario, even though it is directly applicable to protocols such as fair SMPC or multi-party contract signing. We further generalize our protocol to work for any exchange topology. 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 even against a malicious TTP.We construct an asymptotically optimal (for the complete topology) 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. We enable the parties to efficiently exchange any item that can be efficiently put into a verifiable escrow (e.g., signatures on a contract). We show how to apply this protocol on top of any SMPC protocol to achieve a fairness guarantee with very little overhead, especially if the SMPC protocol works with arithmetic circuits. Our protocol guarantees fairness in its strongest sense: even if all n − 1 other participants are malicious and colluding, fairness will hold.

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Section: Related Workmentioning

confidence: 99%

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

Kılınç

Küpçü

2015

Lecture Notes in Computer Science

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“…T performs a deterministic decision procedure, shown in Algorithm 1, on the received message and existing stored messages and immediately sends back "abort" or the list of signatures (S P (C)) P ∈A . Our decision procedure is based on [10,17]. The input to the algorithm consists of a message m received by the T from a signer and state information which is maintained by T. T extracts the contract and the DAG MPCS protocol specification from m. For each contract C, T maintains the following state information.…”

Section: Resolve Protocolmentioning

confidence: 99%

Generalizing Multi-party Contract Signing

Mauw

Radomirović

2015

Lecture Notes in Computer Science

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Multi-party contract signing (MPCS) protocols allow a group of signers to exchange signatures on a predefined contract. Previous approaches considered either completely linear protocols or fully parallel broadcasting protocols. We introduce the new class of DAG MPCS protocols which combines parallel and linear execution and allows for parallelism even within a signer role. This generalization is useful in practical applications where the set of signers has a hierarchical structure, such as chaining of service level agreements and subcontracting. Our novel DAG MPCS protocols are represented by directed acyclic graphs and equipped with a labeled transition system semantics. We define the notion of abort-chaining sequences and prove that a DAG MPCS protocol satisfies fairness if and only if it does not have an abortchaining sequence. We exhibit several examples of optimistic fair DAG MPCS protocols. The fairness of these protocols follows from our theory and has additionally been verified with our automated tool. We define two complexity measures for DAG MPCS protocols, related to execution time and total number of messages exchanged. We prove lower bounds for fair DAG MPCS protocols in terms of these measures.

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“…It is difficult to ascertain whether or not a cryptographic protocol satisfies its security requirements. Numerous protocols have appeared in literature and have subsequently been found to be flawed [13,14,5]. Typically, cryptographic protocols are expected to achieve their objectives in the presence of an attacker that is assumed to have full control of the network (sometimes called the Dolev-Yao attacker).…”

Section: Introductionmentioning

confidence: 99%

Automatic Verification of Privacy Properties in the Applied pi Calculus

Delaune

Ryan

Smyth

IFIP – The International Federation for Information Processing

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We develop a formal method verification technique for cryptographic protocols. We focus on proving observational equivalences of the kind P ∼ Q, where the processes P and Q have the same structure and differ only in the choice of terms. The calculus of ProVerif, a variant of the applied pi calculus, makes some progress in this direction. We expand the scope of ProVerif, to provide reasoning about further equivalences. We also provide an extension which allows modelling of protocols which require global synchronisation. Finally we develop an algorithm to enable automated reasoning. We demonstrate the practicality of our work with two case studies.

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Fair multi-party contract signing using private contract signatures

Cited by 26 publications

References 6 publications

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

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

Generalizing Multi-party Contract Signing

Automatic Verification of Privacy Properties in the Applied pi Calculus

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