Secure electronic commerce with mobile agents

Online transactions using mobile agents need secure protocols to help the mobile agents to accomplish the transactions initiated by a client in an electronic commerce. However, the mobile agent could encounter hostile environment. For example, a server may compromise the mobile agent and try to obtain private information of the client. A solution to tackle this issue has been proposed. However, the existing solution is implemented using RSA signatures that result in long signatures and heavy workloads for the mobile agent. Mobile agents will migrate from the client to a server and from one server to other servers in order to accomplish the client?s transaction plan. Therefore, it will be interesting to re-tackle this issue. We present a new scheme for secure transactions using mobile agents in potentially hostile environments. This transaction scheme is implemented by using a new undetachable signature scheme. The new undetachable signature protocol utilizes short signatures, which is desirable for low-bandwidth and efficient mobile communications

Secure e-transactions using mobile agents with agent broker

This paper presents an e-transactions protocol using mobile agents. However, when mobile agents travel to a number of servers for searching optimal purchase for the underlying customer, the mobile codes should be protected. We integrate a secure signature algorithm with the e-transaction algorithm to maintain the security. In addition, an agent broker is involved in the algorithm that will help to reduce the communications among the mobile agents, the customer, and the servers. We have presented security and privacy analysis for the proposed protocol

Short Signatures, Provable Security, Generic Attacks and Computational Security of Multivariate Polynomial Schemes such as HFE, Quartz and Sflash

The object of this paper is the concrete security of recent multivariate signature schemes. A major challenge is to reconcile some "tricky" ad-hoc constructions that allow to make short signatures, with regular provable security. The paper is composed of two parts

A method of Weil sum in multivariate quadratic cryptosystem

A new cryptanalytic application is proposed for a number theoretic tool Weil sum to the birthday attack against multivariate quadratic trapdoor function. This new customization of the birthday attack is developed by evaluating the explicit Weil sum of the underlying univariate polynomial and the exact number of solutions of the associated bivariate equation. I designed and implemented new algorithms for computing Weil sum values so that I could explicitly identify some class of weak Dembowski- Ostrom polynomials and the equivalent forms in the multivariate quadratic trapdoor function. This customized attack, also regarded as an equation solving algorithm for the system of some special quadratic equations over finite fields, is fundamentally different from the Grobner basis methods. The theoretical observations and experiments show that the required computational complexity of the attack on these weak polynomial instances can be asymptotically less than the square root complexity of the common birthday attack by a factor as large as 2^(n/8) in terms of the extension degree n of F2n. I also suggest a few open problems that any MQ-based short signature scheme must explicitly take into account for the basic design principles