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Design and development of crytographic fair exchange protocols

Cagil Can Oniz

Published Jan 1, 2004• 0 citations
OpenAlex

Abstract

In this thesis, the problem of fair exchange on specific cases is addressed. The main idea of fair exchange is as follows: Two entities that do not trust each other want to exchange some arbitrary data over a communication network. Since they do not trust each other, neither party wants to transmit their own data before receiving the other entity's data. Even though either party could prove an unjust situation after termination of the protocol, if they are in different countries, solving disputes may require time and money due to the bureaucracy of international laws. In this thesis, a special application of fair exchange, a fair e-commerce protocol for large e-goods is designed and implemented. The proposed protocol provides a method for fair exchange of e-money to e-products, and a method for verifying the contents of the exchanged items. The presented protocol is efficient such that when none of the parties tries to cheat, only three messages are sufficient. In case of disputes, three more messages are needed. Furthermore, in most of the previously proposed protocols in the literature, e-goods are transferred multiple times among some entities. This situation is too costly when e-goods are large. In the presented protocol, e-goods are transferred only once. Another important property of the protocol is the anonymity of the customer; no information about the customers shopping habits can be gathered through the protocol. The implementation results show that the protocol is efficient and secure and that small number of cryptographic operations is sufficient. In addition to the fair e-commerce protocol, another special application of fair exchange, a fair multimedia exchange protocol using a different method is designed and implemented. This protocol is designed due to different requirements of different applications. In the fair multimedia exchange protocol, two entities want to exchange some multimedia files such as video or audio files. This protocol requires lower security and has a different a lower degree of fairness as compared to the fair e-commerce protocol. Fair multimedia exchange protocol uses a baby-step approach in which the probability of protocol completion is gradually increased over several cycles. In baby-step approach protocols, entities exchange pieces of the items, which they want to barter. At protocol completion, the complete items are formed by using the pieces exchanged.

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In this thesis, the problem of fair exchange on specific cases is addressed. The main idea of fair exchange is as follows: Two entities that do not trust each other want to exchange some arbitrary data over a communication network. Since they do not trust each other, neither party wants to transmit their own data before receiving the other entity's data. Even though either party could prove an unjust situation after termination of the protocol, if they are in different countries, solving disputes may require time and money due to the bureaucracy of international laws. In this thesis, a special application of fair exchange, a fair e-commerce protocol for large e-goods is designed and implemented. The proposed protocol provides a method for fair exchange of e-money to e-products, and a method for verifying the contents of the exchanged items. The presented protocol is efficient such that when none of the parties tries to cheat, only three messages are sufficient. In case of disputes, three more messages are needed. Furthermore, in most of the previously proposed protocols in the literature, e-goods are transferred multiple times among some entities. This situation is too costly when e-goods are large. In the presented protocol, e-goods are transferred only once. Another important property of the protocol is the anonymity of the customer; no information about the customers shopping habits can be gathered through the protocol. The implementation results show that the protocol is efficient and secure and that small number of cryptographic operations is sufficient. In addition to the fair e-commerce protocol, another special application of fair exchange, a fair multimedia exchange protocol using a different method is designed and implemented. This protocol is designed due to different requirements of different applications. In the fair multimedia exchange protocol, two entities want to exchange some multimedia files such as video or audio files. This protocol requires lower security and has a different a lower degree of fairness as compared to the fair e-commerce protocol. Fair multimedia exchange protocol uses a baby-step approach in which the probability of protocol completion is gradually increased over several cycles. In baby-step approach protocols, entities exchange pieces of the items, which they want to barter. At protocol completion, the complete items are formed by using the pieces exchanged.
One of the most crucial factors that e-commerce protocols should address is a fair exchange. In this research, an advanced method of cryptography coupled with the pay per use technique is used. A new electronic commerce protocol for the exchange of commodities is introduced. The proposed new protocol guarantees both features while addressing the main drawbacks associated with other related protocols. The new suggested e-commerce protocol is composed of two stages: pre-exchange and exchange stages. When the suggested new protocol is analysed with scrupulous protocol analysis, it attains fair exchange and a secure method of payment. The suggested new e-commerce protocol is more efficient than other related existing protocols. In this research “protocol prototype” and “model checking” is used for the purpose of authentication. The protocol prototype verifies that the suggested new protocol is executable when it's used in a real context. By experimental designs, this research shows the length of asymmetric keys as the biggest element that affects the efficiency of the protocol. When model-checking is applied in this protocol, the outcome indicates that the suggested protocol achieves the required features of fairness. Protocol extensions give those involved in the protocol the capacity to be resilient to failure. By using three methods of authentication, this research confirms that the new proposed protocol is well formulated. The work reported in this thesis first study the existing fair exchange protocols that solve the fairness problem. Then, propose more efficient protocol to solve the fairness problem. The original idea in this thesis is to reduce the communication overheads, risks and solve the bottleneck problems in the protocols that involve an online TTP.
We present protocols for fair exchange of electronic data (digital signatures, payment and confidential data) between two parties A and B. Novel properties of the proposed protocols include: 1) offline trusted third party (TTP), i.e., TTP does not take part in the exchange unless one of the parties behaves improperly; 2) only three message exchanges are required in the normal situation; 3) true fair exchange, i.e., either A and B obtain each other's data or no party receives anything useful; no loss can be incurred to a party no matter how maliciously the other party behaves during the exchange. This last property is in contrast to previously proposed protocols with offline TTP ([1] and [21]), where a misbehaving party may get another party's data while refusing to send his document to the other party, and the TTP can provide affidavits attesting to what happened during the exchange. To our knowledge, the protocols presented here are the first exchange protocols which use offline TTP and at the same time guarantee true fair exchange of digital messages. We introduce a novel cryptographic primitive, called the Certificate of Encrypted Message Being a Signature (CEMBS), as the basic building block of the fair exchange protocols. It is used to prove that an encrypted message is a certain party's signature on a public file, without revealing the signature. We also give two examples to show in detail how the certificate can be constructed.
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.
A key problem of electronic commerce (for short e-commerce) is fair exchange which guarantees that at the end of the transaction, either both parties in the transaction receive each other's items or none do. A non-interactive optimistic fair exchange e-commerce protocol model based on the publicly verifiable secret sharing is presented. The main idea of our exchange protocol is to interchange verifiable and recoverable keys of the symmetric encryption for participants' items. So it is especially suitable for exchange of large-size items. Furthermore, our protocol is efficient and simple as it does not need interactive proof system which has been adopted by a large quantity of previously proposed fair exchange protocols. Based on a modified (2,2) secret sharing scheme, a concrete non-interactive fair exchange e-commerce protocol is designed.
Fairness is the basic requirement of E-Commerce protocols. RSA is one of the most widely used cryptosystems. A fair-exchange protocol allows two parties to exchange items in a fair way so that either each party gets the other's item, or neither party does. In this paper construction and architecture of the existing fair exchange protocols are analyzed. Both practicality and efficiency problems of these protocols are also presented. Based on this analysis, an optimistic fair exchange protocol totally based on RSA signature scheme is proposed. The novel scheme employs verifiably encrypted RSA signatures in the extended integer ring that is elaborately constructed. The security and efficiency of the newly devised scheme are also proved and examined. It is showed that the proposed scheme is secure and efficient.
With the advancement in Internet-based technologies, network applications are no longer just limited to one-to-one communication; instead, it has become a publicly accessible resource. Regardless of this growth, such applications bring specific challenges concerning authentication, integrity, and privacy. Cryptography stands as an ideal solution to overcome these issues through an interactive method of secure communication called Key Exchange. Key exchange protocols allow two or more entities to agree upon a shared secret transmitted over a public channel without revealing any information to an eavesdropper. This thesis contributes to the design and analysis of the variants of key exchange protocols along with their applications. As per the security requirements, the proposed schemes are either designed in an interactive model or a non-interactive model. Each scheme undergoes a series of formal and informal security analysis. The formal analysis provides simulation result using cryptographic models. Whereas, an informal analysis showcases the theoretical proves on known attacks where an adversary controls the network. The performance analysis maps the protocol’s efficiency based on the computation cost and communication size. The first contribution introduces an interactive two-party authenticated key exchange protocol. We begin by investigating the security flaws in an existing system such as, lack of user anonymity, trace attack, clogging attack, and failure to resist replay attack. Then proposed an authenticated self-certified key exchange protocol that overcomes the addressed issues. Also, it eliminates the requirements of a trusted certificate authority to authorize the entities. The scheme achieves anonymity during session execution, mutual authentication and enables session key agreement.Based on the ideology, an application is designed, forsecure communication between ad-hoc nodes in a mobile ad-hoc network. The second contribution contributes to the design of an Identity-based authenticated three-party key exchange protocol that overcomes the incapability of managing huge peer-to-peer communication and high computation cost faced by two-party authenticated key exchange protocols. The proposed scheme preserves user privacy by enabling the property of anonymity and ensures non-repudiation. Based on the ideology, an application is designed to establish a secure session key between two users with the help of a trusted server for an electronic payment system. The third contribution proposes an interactive pairing-free certificateless authenticated group key agreement scheme suitable for a resource constrained mobile network. The scheme allows any user to join or leave the group dynamically. The key agreement protocol devised in this scheme ensures un-deniability property by incorporating the signcryption, and unsigncryption algorithm. The final contribution presents a non-interactive Identity-based deniable authentication protocol that allows an intended receiver to identify the origin of a given message without being able to prove sender’s identity to a third party.