Online digital contract signing in mistrusted parities

Online digital contract signing in mistrusted parities

ABSTRACT

A fair contract signing protocol allows two potentially mistrusted parities to exchange their commitments (i.e., digital signatures) to an agreed contract over the Internet in a fair way, so that either each of them obtains the other’s signature, or neither party does. Based on the RSA signature scheme, a new digital contract signing protocol is proposed in this paper. Like the existing RSA-based solutions for the same problem, our protocol is not only fair, but also optimistic, since the third trusted party is involved only in the situations where one party is cheating or the communication channel is interrupted. Furthermore, the proposed protocol satisfies a new property, i.e., it is abuse-free. That is, if the protocol is executed unsuccessfully, none of the two parties can show the validity of intermediate results to others. Technical details are provided to analyze the security and performance of the proposed protocol. In summary, we present the first abuse-free fair contract signing protocol based on the RSA signature, and show that it is both secure and efficient.

EXISTING SYSTEM

Contract signing is truly simple due to the existence of “simultaneity”. That is, both parties generally sign two hard copies of the same contract at the same place and at the same time. After that, each party keeps one copy as a legal document that shows both of them have committed to the contract. If one party does not abide by the contract, the other party could provide the signed contract to a judge in court. As the electronic commerce is becoming more and more important and popular in the world, it is desirable to need a mechanism that allows two parties to sign a digital contract via the Internet. However, the problem of contract signing becomes difficult in this setting, since there is no simultaneity any more in the scenario of computer networks. In other words, the simultaneity has to be mimicked in order to design a digital contract signing protocol. This requirement is essentially captured by the concept of fairness.

PROPOSED SYSTEM

In this Project we mainly focus on the problem of digital contract signing. Since a
party’s commitment to a digital contract is usually defined as his/her digital signature on the contract, digital contract signing is essentially implied by fair exchange of digital signatures
between two potentially mistrusted parities. There is a rich history of contract signing (i.e., fair exchange of digital signatures) because this is a fundamental problem in electronic transactions. According to the involvement degree of a trusted third party (TTP), contract signin protocols can be divided into three types: (1) gradual exchanges without any TTP; (2) protocols with an on-line TTP; and (3) protocols with an off-line TTP. Early efforts mainly focused on the first type protocols to meet computational fairness: Both parties exchange their commitments/secrets “bit-by-bit”. If one party stops prematurely, both parties have about the same fraction of the peer’s secret, which means that they can complete the contract off-line by investing about the same amount of computing work. The major advantage of this approach is that no TTP is involved. However, this approach is unrealistic for most real-world applications due to the following several reasons. First of all, it is assumed that the two parties have equivalent computation resources. Otherwise, such a protocol is favorable to the party with stronger computing power, who may conditionally force the other party to commit the contract by its own interest. At the same time, such protocols are inefficient because the costs of computation and communication are extensive. In fair exchange protocols an on-line TTP is always involved in every exchange. In this scenario, a TTP is essentially a mediator: (a) Each party first sends his/her item to the TTP; (b) Then, the TTP checks the validity of those items; (c) If all expected items are correctly received, the TTP finally forwards each item to the party who needs it. Generally speaking, contract signing protocols with an on-line TTP could be designed more easily since the TTP facilitates each step of exchanging, but may be still expensive and inefficient because the TTP needs to be paid and must be part of every execution. In practice, the TTP is prone to become a bottleneck in the whole system, especially in the situation where many users rely on a single TTP.

Hardware Requirements:

• System : Pentium IV 2.4 GHz.
• Hard Disk : 40 GB.
• Floppy Drive : 1.44 Mb.
• Monitor : 15 VGA Colour.
• Mouse : Logitech.
• Ram : 512 Mb.

Software Requirements:-

Language : Java / Dot Net

OS : Windows XP

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