Key Management In Asynchronous Network And Ad Hoc Network

In this dissertation, two protocols on secret sharing under different system models are provided. One is asynchronous secret sharing in wired network that has no synchronous assumption . The other is distributed hierarchical key management in Ad-hoc network.We must take into account some aspects in the construction of applicable secret sharing scheme. First of all access structure should be determined according to practical requirements. Next question arose is whether verified or publicly verified scheme should be used which depend on computational capabilities of participants and capabilities of adversaries. If there is more than one secret to be shared, multi-secret scheme should be adopted. Long lived secret shares in network exposed to attacks and break-ins are insecure, periodic share updating could prevent the adversary from learning the secret or destroying it. While sharcs are likely to be lost for hardware failure or damages, share recovery algorithm is necessary. Designing proactive secret sharing scheme should base on an efficient communication protocol in particular network environment.Most proactive secret sharing schemes assume a synchronous system. In this model, a common clock exists; bounds on message delays and execution speed of processor are known. The unrealistic assumption may lead to denial of service attacks by delaying messages or consuming processor cycles. An asynchronous secret sharing scheme is presented in which integrity and availability are guaranteed when internal adversaries exist. Both communication complexities and message complexities are reduced compared with previous protocols. Proof of security and correctness is given.Traditional centralized and static key management is not appropriate to ad hoc networks due to its dynamically changed topology and low trustworthiness of single node. A new distributed key management scheme based on hierarchical secret sharing in ad-hoc is presented. In this scheme, nodes were divided into two parts, server nodes and ordinary nodes. The shares held by server nodes include more information than ordinary nodes. Any it nodes (including at least k₁ server nodes) collaborate to reconstruct the secret key. The scheme improves the availability of the key service in ad-hoc compared with the scheme in...