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IEEE Conference on Commerce and Enterprise Computing (CEC)

Certified e-Mail Protocol with Verifiable Third Party

Macià Mut–Puigserver, Josep Lluís Ferrer Gomila, Llorenç Huguet Rotger

Published Apr 12, 2005• 12 citations
Publisher

Abstract

Certified e-mail is a particular case of fair exchange. TTPs play an important role in this kind of protocols and their reliability and security is a problem that needs to be addressed. In order to enhance the trust in non-repudiation services we propose TTPs that provide verifiable services, so users get evidence of the TTPs operations. In this paper we design a new certified e-mail protocol where the user confidence on what is happening when he invokes the TTP is enhanced.

DOI
10.1109/eee.2005.46

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Certified e-mail is a particular case of fair exchange. TTPs play an important role in this kind of protocols and their reliability and security is a problem that needs to be addressed. In order to enhance the trust in non-repudiation services we propose TTPs that provide verifiable services, so users get evidence of the TTPs operations. In this paper we design a new certified e-mail protocol where the user confidence on what is happening when he invokes the TTP is enhanced.
Electronic mail delivery is one of the most important and desirable services, by which the intended recipient will get the mail if and only if the mail originator receives a valid and irrefutable proof of the receipt. The idea of conditional trusted third party has been developed on the basis of semi-trusted TTP and a suite of acceptable conditions is given. A new practical protocol for certified e-mail is presented, which can guarantee acceptable fair with interception of conditional TTP. More, the evidence in the new protocol is publicly verifiable without any restrictions on the type of signature and encryption algorithms.
A non-repudiation protocol enables the fair exchange of an electronic message and an irrefutable digital receipt between two mistrusting parties over the Internet. That is, at the end of any execution instance of such a protocol, either both parties obtain their expected items or neither party does . In this paper, we first argue that it is really meaningful in practice to exploit generic fair non-repudiation protocols with transparent off-line trusted third party (TTP). Namely, in those protocols, each involved party could use any secure digital signature algorithm to produce non-repudiation evidences; and the issued evidences are the same regardless of whether the TTP is involved or not. Then, we present such a fair non-repudiation protocol to overcome some limitations and shortcomings in previous schemes. Technical discussions are provided to show that our protocol is not only secure but also the most efficient solution, compared with existing non-repudiation protocols. In addition, some potential extensions are also pointed out.
In this paper, a new fair certified email protocol is proposed. The proposed protocol uses offline trusted third party (TTP) that will only be involved if a party misbehaves, otherwise the TTP is inactive. The protocol is based on the verifiable and recoverable encryption of keys. In this regard, the recipient of an email will be able to verify if the encrypted key used to encrypt the email is correct. The protocol comprises of only three messages in the exchange sub-protocol and three messages in the recovery sub-protocol. The proposed protocol is more efficient compared with related protocols.
Non-repudiation service is widely employed in information exchange and online transaction. It requires that its participants are unable to deny their involvement in specific protocol. At the same time, the service should keep fairness, which means that no one could take any advantages over the other one. Researchers have introduced a trusted third party (TTP) to realize these demands. Protocols are grouped into several categories according to the degree of TTP's involvement in protocols. Optimistic non-repudiation protocol is the most important method undoubtedly owe to its lower TTP's involvement. There are two questions. One is that whether it is possible to further decrease TTP's involvement or not. A computable optimistic non-repudiation protocol seems to be a good improvement. This is also our paper's basic protocol. The other question is about whether two types of finally evidences that produced by participants (here is Alice and Bob, and we denote this type evidences as the first type evidences) and TTP (or with the help of TTP, and we demote this type evidences as the second type evidences) are identical. If both types of evidences are not exactly the same, then it shows that TTP has taken part in process of protocol. Thus, it is certain that either participants behaved dishonest, or network went wrong. Participants' prestige will be negatively affected more or less. On the contrary, if two types of evidences are identical, then such feelings will be eliminated. This kind of TTP is called transparent TTP. In this paper, we have accomplished an optimistic non-repudiation protocol with the help of transparent TTP based on a computable non-repudiation protocol.
A certified electronic mail protocol must avoid the selective receipt of messages in notification operations. No author based selective receipt is a desired feature for certified electronic mail protocols because the receiver must accept or reject the message before the identity of the sender is revealed. We present a certified e-mail protocol, based in our previous protocol presented in the International Security Workshop 2000, which avoids selective receipt. The modified protocol does not use the signature of the sender in the first step of the protocol and avoids temporally the identification of the sender. However, even without this signature, the protocol presents a dispute resolution system that avoids unfair situations. The result is a fair, asynchronous and efficient protocol. Moreover we have evaluated the role of the TTP in the fair exchange protocol, showing that the incorrect behavior of the TTP can be demonstrated in all cases, so the TTP is verifiable.