A Secure and Efficient Key Exchange Protocol for Mobile Communications

This paper proposes a key exchange protocol with mutual authentication, which requires only 0.1 modular multiplications for online computations. This online computation is ten times faster than that of conventional protocols. The message size of the proposed protocol is about half (50%~66%) that of the previous protocols. In addition to its efficiency in online computation and bandwidth, the paper provides a formal proof to guarantee the security of the proposed protocol. Possessing of both secure and efficient properties makes the proposed protocol suitable for the low power mobile communications

An Enhanced and Secure Protocol for Authenticated Key Exchange

An enhanced authentication key exchange protocol was proposed to exchange multiple session keys between two participants at a time. This paper shows that this enhanced protocol is insecure under the known session key attack, known long-term private key attack, signature forgery attack, and replay attack. This paper also proposes an enhanced and secure key agreement protocol for exchanging multiple session keys in one run of the protocol. The protocol is secure against the attacks mentioned above. Besides, a formal proof is given to guarantee the security of the proposed protocol under other potential attacks

Cryptanalysis of a threshold proxy signature with known signers

A scheme of threshold proxy signature with known signers was proposed by Hwang et al. In their scheme, the receiver can identify the proxy signers that actually generated a proxy signature. Tzeng et al. demonstrated that this signature scheme is insecure and proposed an improvement to mend the information leakage. This paper shows that the improved scheme is still insecure under the original signer¡¦s forgery attack

On the Security of Image Encryption Method

[[abstract]]Alexopoulos, Bourbakis and Ioannou proposed two cryptographic schemes for encrypting 2-D gray scale images by using a large family of fractals respectively. Their schemes are based on a transposition of the image elements. However, their schemes will be vulnerable in case that they employ the unique key in their proposed system. In this paper, we show that their transposition encryptions can easily be broken with a pair of plain-image and cipher-sequential data. Meanwhile, we offer some suggestions for 2-D image transposition encryption

A Threshold Signature Scheme Withstanding the Conspiracy Attack

[[abstract]]A threshold signature, first proposed by Desmedt and Frankel, allows or more members of the group cooperate to generate a signature on behalf of the group while providing the anonymity of the signers. Unfortunately, all threshold signature schemes proposed so far can not withstand the conspiracy attack, thus the group secret key can be revealed. In this paper, we propose a new threshold signature scheme to avoid the conspiracy attack. The security of the proposed threshold signature scheme is based on the difficulty of computing the discrete logarithm modulo for a composite number. The size of the group signature and the verification time of the group signature are equivalent to that of an individual signature

New Digital Signature with Subliminal Channels Based on the Discrete Logarithm Problem

[[abstract]]A digital signature with a subliminal channel, that allows a signer to embed subliminal messages in the digital signature. Any receivers may verify the signature, but can not discover the subliminal messages, only authorized receivers can extract the subliminal messages. In this paper we propose two digital signature schemes with subliminal channels based on discrete logarithms. Both schemes allow a signer to generate a digital signature, which may contain two or more subliminal messages for various subliminal receivers. Compared to the previously proposed schemes, both our schemes greatly reduce the size of secret keys that must be kept by the signer and the subliminal receiver; as well as the length of the digital signature. The security of the proposed schemes is based on the difficulty of computing the discrete logarithm proble