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Design and evaluate a fair exchange protocol based on online trusted third party (TTP)

Abdullah Shawan Alotaibi

Published Jan 1, 2012• 1 citation
OpenAlex

Abstract

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.

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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.
Customers are usually passive in an electronic commerce transaction. Based on a new two times concurrent signature, this article presents a fair electronic payment (E-payment) protocol. It can protect both of the participants' profits. Whatpsilas more, in this protocol customers have more initiative, and they can terminate the transaction before possible cheats (while they also should be responsible for the quit), so their security is enhanced. As there is no traditional trusted third party (TTP) in our scheme, network congestion and conspiracy problem can be avoided. Moreover, the protocol satisfies fairness and non-repudiation, and it can also be applied in the digital signature or product exchange process.
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.
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.
Making use of the idea of convertible digital signature, this paper proposes a new fair electronic payment scheme based on a new interactive verification protocol that is proposed in the paper too. The security of the scheme is based on the hard question of discrete logarithm. The scheme makes both sides in equal positions during the course of electronic transaction. And then, the fairness of electronic transaction is achieved. A trusted third party (TTP) is involved in the scheme to guarantee the fairness of the scheme for both sides. However, only during the course of registration and dispute resolution will TTP be needed. TTP is not needed during the normal payment stage. That is to say, it does not affect efficiency of payment to involving TTP. So the scheme is a fair electronic payment scheme in optimistic sense.