This paper describes a new protocol for authentication in ad-hoc networks. The protocol has been designed to meet specialized requirements of ad-hoc networks, such as lack of direct communication between nodes or requirements for revocable anonymity. At the same time, a ad-hoc authentication protocol must be resistant to spoofing, eavesdropping and playback, and man-in-the-middle attacks. The article analyzes existing authentication methods based on the Public Key Infrastructure, and finds that they have several drawbacks in ad-hoc networks. Therefore, a new authentication protocol, basing on established cryptographic primitives (Merkle's puzzles and zero-knowledge proofs) is proposed. The protocol is studied for a model ad-hoc chat application that provides private conversations.
Mobile agents have recently started being deployed in large-scale distributed systems. However, this new technology brings some security concerns of its own. In this work, we propose a security scheme for protecting mobile agent platforms in large-scale systems. This scheme comprises a mutual authentication protocol for the platforms involved, a mobile agent authenticator, and a method for generation of protection domains. It is based on SPKI SDSI chains of trust, and takes advantage of the flexibility of the SPKI SDSI certificate delegation infrastructure to provide decentralized authorization and authentication control. Mobile agent technology offers a new computing paradigm in which a program, in the form of a software agent, can suspend its execution on a host computer, transfer itself to another agent-enabled host on the network, and resume execution on the new host. The use of mobile code has a long history dating back to the use of remote job entry systems in the 1960's. Today's agent incarnations can be characterized in a number of ways ranging from simple distributed objects to highly organized software with embedded intelligence. As the sophistication of mobile software has increased over time, so too have the associated threats to security. This report provides an overview of the range of threats facing the designers of agent platforms and the developers of agentbased applications. The report also identifies generic security objectives, and a range of measures for countering the identified threats and fulfilling these security objectives. New portable computers and wireless communication technologies have significantly enhanced mobile computing. The emergence of network technology that supports user mobility and universal network access has prompted new requirements and concerns, especially in the aspects of access control and security. In this paper, we propose a new approach using authorisation agents for cross-domain access control in a mobile computing environment. Our framework consists of three main components, namely centralised authorisation servers, authorisation tokens and authorisation agents. An infrastructure of centralised authorisation servers and application servers from different domains is proposed for supporting trust propagation to mobile hosts instantaneously. While the authorisation token is a form of static capability, the authorisation agent on the client side can be regarded as a dynamic capability to provide the functionality in client-server interactions. It works collaboratively with remote servers to provide authorisation service with finer access granularity and higher flexibility. In mobile agent systems, program code together with some process state can autonomously migrate to new hosts. Despite its many practical benefits, mobile agent technology results in significant new security threats from malicious agents and hosts. In this paper, we propose a security architecture to achieve three goals: certification that a server has the authority to execute an agent on behalf of its sender; flexible selection of privileges, so that an agent arriving at a server may be given the privileges necessary to carry out the task for which it has come to the server; and state appraisal, to ensure that an agent has not become malicious as a consequence of alterations to its state. The architecture models the trust relations between the principals of mobile agent systems and includes authentication and authorization mechanisms.