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Security and privacy are crucial to the wide deployments of delay tolerant networks. Without security and privacy guarantees, people are reluctant to accept such a new network paradigm. To address the security and privacy issues in delay tolerant networks, in this paper, based on ID-based ring signatures and Merkle hash tree techniques, we present a new efficient anonymous authentication mechanism. The newly proposed mechanism not only achieves good security properties, including authentication, anonymity and confidentiality, but also has strong robustness and high efficiency.

Recently, the self-certified public key system, due to its advantages, has been paid a great deal of attention. Over the past years, many self-certified digital signature schemes have been proposed. However, to the best of our current knowledge, self-certified one-time short signature has not been investigated till now. Therefore, in this paper, we would like to propose an efficient self-certified one-time short signature scheme from bilinear pairing techniques. Because of its one-timeness and unforgeability, the proposed scheme can be suitable for the electronic cheque scenario. Moreover, the size of the proposed signature scheme is as short as 160 bits since it is based on the BLS short scheme, which shows that the proposed scheme has a great advantage while the bandwidth of a communication channel is limited.

The concept of designated verifier signatures was first introduced by Chaum and by Jakobsson, Sako and Im-pagliazzo independently in the middle of the 1990's, and then generalized by Desmedt at Crypto'03 rump session. Since a designated verifier signature can be only verified by a unique and specific user, the designated verifier signature scheme has been deeply studied and widely used in many applications for electronic voting or electronic auction. Most recently, Kang, Boyd, and Dawson proposed a novel identity-based strong designated verifier signature scheme from bilinear pairing and used the provable security technique to prove the security of the scheme. However, in this paper, we show that Kang et al.'s scheme can't resist some existential forgery attack and therefore propose an improved version with a slight modification to avoid the attack.

Deniable authenticated protocol is a new cryptographic authentication protocol that enables an intended receiver to identify the source of a given message without being able to prove the identity of the sender to a third party. Therefore, it can be applied to many practical situations. Over the past years, plenty of deniable authentication protocols have been put forth. In this paper, based on the elliptic curve cryptosystem, we would like to propose a novel group oriented deniable authentication protocol. In our proposed protocol, the number of the senders reaches the qualified threshold value, and then these senders can send a deniable authentication message to an intended receiver.

A proxy signature enables an original signer to delegate her signing capability to a proxy signer and the proxy signer can sign a message on behalf of the original signer. Later, anyone accessible to the public keys of the original signer and proxy signer and the corresponding delegation warrant is able to verify the authenticity of a purported proxy signature. Obviously, the "public-verifiable" property here is quite suitable in most application scenarios, however, it is not applicable for some other applications, as in the case that a proxy signed message may be personally or commercially sensitive, for example, in a bill of tax or a bill of health, etc. Thereby, aim at these applications, several designated verifier proxy signature schemes have recently been suggested. However, to our best knowledge, none of these schemes has provided the provable security proof. Therefore, in this paper, based on the bilinear pairing, we would like to propose a new designated verifier proxy signature scheme, and apply the techniques from provable security to analyze its security.

Quite recently [IEEE Commu. Letters, Vol. 13, No. 5, 2009], Huang and Cao proposed a novel and efficient unlinkable secret handshakes scheme claiming to provide unlinkability and better performance than previously reported ones. In this paper, we will point out their scheme has a serious security loophole due to an inherent design flaw. Thus, we hope that by identifying the design flaw, similar mistakes can be avoided in future unlinkable secret handshakes designs.