We present composite key management, a novel paradigm for key management in ad hoc networks. While most existing approaches try to fit techniques developed for wired environments into ad hoc networks, our approach works within the specific limitations of ad hoc networks to increase security and availability of the key management framework. By composing techniques from PKI and certificate chaining, composite key management follows two fundamental principles that must be satisfied by an ad hoc key management framework: node participation and the use of a trusted third party. We introduce enhanced metrics of authentication to aid end users in understanding and using the key management framework. Through simulation studies, we demonstrate the effectiveness of composite key management under stressful scenarios where previous approaches fail and show that composite key management can address the challenges posed by the unique nature of ad hoc networks.

The characteristics of ad hoc networks naturally encourage the deployment of distributed services. Although current networks implement group communication methods, they do not support the needs of a mobile node that must locate one or more distributed servers. A node should not need detailed knowledge of network topology to choose servers with which it can communicate efficiently.To this end, manycast is a group communication scheme that enables communication with an arbitrary (user specified) number of group members. Anycast and multicast communication are special cases of manycast in which the target number of group members is one and infinity, respectively. We present manycast and discuss its use as a communication primitive, with specific attention to ad hoc networks. We advocate manycast support at the network layer. A manycast routing protocol enables an application to contact several nearby network nodes that implement a distributed service.We analyze some approaches to manycast, including some application layer implementations. This evaluation supports our claim that manycast must be implemented in the network layer for effective operation in ad hoc networks. We present several extensions to ad hoc routing protocols that can provide manycast support with minimal implementation effort. Through analysis and extensive simulation, we explore the behavior of these approaches to manycast, finally providing recommendations to implementors.

ARP handles neighbor discovery and address resolution in infrastructure networks, but is inadequate for mobile ad hoc networks (MANETs). Thus, many MANET routing protocols include a neighbor discovery mechanism. This separation of neighbor discovery and address resolution is a fundamental design problem that causes packet loss, particularly when the communication is manycast, a novel variant of multicast communication. Our approach, automatic address resolution, moves address resolution into the routing protocol along with neighbor discovery, correcting these problems.

Ubiquitous computing is poised to revolutionize the way we compute and interact with each other. However, unless privacy concerns are taken into account early in the design process, we will end up creating a very effective distributed surveillance system, which would be a dream come true for electronic stalkers and "big brothers". We present a protocol, which preserves the privacy of users and keeps their communication anonymous. In effect, we create a "mist" that conceals users from the system and other users. Yet, users will still be able to enjoy seamless interaction with services and other entities that wander within the ubiquitous computing environment.

Since its birth more than two decades ago, public key cryptography has been recognized as one of the most effective mechanisms for providing fundamental security services including authentication, digital signatures and encryption for dynamic networks. Effective management of keys, or digital certificates holding the keys, is one of the key factors for the successful wide-spread deployment of public key cryptography. The public key infrastructure (PKI ), an infrastructure for managing digital certificates, was introduced for this purpose. The most important component of PKI is the certificate authority (CA), the trusted entity in the system that vouches for the validity of digital certificates. This work describes a framework to provide efficient yet effective distributed CA service for ad hoc wireless networks. We select physically or computationally more secure nodes as MOCAs (MObile Certificate Authority) and use threshold cryptography to distribute the CA's private key among these MOCA nodes. We also provide a protocol for clients to contact MOCAs and get certification services without incurring excessive overhead.