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IEEE International Conference on Computational Science and Engineering (CSE) and IEEE International Conference on Embedded and Ubiquitous Computing (EUC)

Extending a Key-Chain Based Certified Email Protocol with Transparent TTP

Zhiyuan Liu, Jun Pang, Chenyi Zhang

Published Dec 1, 2010• 10 citations
Publisher

Abstract

Cederquist et al. proposed an optimistic certified email protocol, which employs key chains to reduce the storage requirement of the trusted third party (TTP). We extend their protocol to satisfy the property of TTP transparency, using existing verifiably encrypted signature schemes. An implementation with the scheme based on bilinear pairing makes our extension one of the most efficient certified email protocols satisfying strong fairness, timeliness, and TTP transparency.

DOI
10.1109/euc.2010.101

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Cederquist et al. proposed an optimistic certified email protocol, which employs key chains to reduce the storage requirement of the trusted third party (TTP). We extend their protocol to satisfy the property of TTP transparency, using existing verifiably encrypted signature schemes. An implementation with the scheme based on bilinear pairing makes our extension one of the most efficient certified email protocols satisfying strong fairness, timeliness, and TTP transparency.
Abstract. As a value-added service for standard email systems, a certified email scheme allows a sender to deliver a message to a receiver in a fair way in the sense that either the sender obtains a receipt from the receiver and the receiver accesses the content of the email simultaneously, or neither party gets the expected item. In this paper, we first point out some weaknesses in several existing schemes. Then, we present two generic optimistic certified email schemes with transparent TTP. Our schemes are not only fair, but also support timeliness in two flavors: one scheme supports weak timeliness but with stateless TTP, while the other guarantees (strong) timeliness though only supports weak stateless TTP. Technical discussion and comparison are provide to show that our schemes are both secure and efficient, compared with the-state-of-art in this field.
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.
A novel certified e-mail protocol that is particularly suitable for mobile environments is described. Our protocol uses an off-line trusted third party (TTP). Protocols with an off-line TTP-also known as optimistic protocols-have numerous practical advantages over protocols with an on-line TTP. Nonetheless, many protocols adopt an on-line TTP primarily because optimistic protocols often entail intricate cryptographic primitives that incur considerable overhead. By using a novel signature paradigm, which we call gradational signatures, we show that it is possible to construct optimistic protocols that are comparable to on-line protocols in terms of computation and communication overhead. This makes our scheme especially desirable in the mobile setting.
While many two-party fair exchange protocols have been proposed, more than three-party fair exchange protocol is required depending on a type of applications. Asokan et al. have proposed a multi-party fair exchange protocol for mesh topology. This scheme can be adapted to all kinds of topologies but requires much communication costs, which is 4n(n-1) passes in the all n-participators honest cases and 8n2-n-10 passes in the worst case. In previous works, more efficient and multi-functional schemes specialized for a kind of topologies have been proposed but most of these are for ring topology and star topology. Zhou et al. have proposed an efficient multi-party contract signing protocol for line topology. It is shown the two protocols such that a simple protocol which is completed with 4(n-1) passes in the all honest cases and 5n-3 passes in the worst case and an optimized protocol which is completed with 3(n-1) passes in the all honest cases and 4n-2 passes in the worst. This result means that a fair exchange protocol for line topology is efficient in a number of communications nevertheless a certified email protocol specialized for line topology has not been proposed. That is, a certified email protocol run on line topology is only a protocol for mesh proposed by Asokan et al. adapted to line topology, therefore there is large room for reducing a number of communications by specializing for a certified email protocol. In this paper, we propose a three-party certified email protocol for line topology towards a design of n-party protocol. The proposed protocol has such basic properties of certified email as fairness, non-repudiation, trusted third party invisibility and timeliness, as same as the previous works. Our scheme is completed with eight passes in the case of all honest and twelve passes in the worst. The communication cost is less than the Asokan et al.'s scheme with 24 (n=3) passes even if the all n-participators are honest.