In search of multiple domain key recovery

Key recovery systems suitable for application among multiple domains, such as those operating within international communication networks, are investigated. A general framework for analysis of key recovery systems is introduced and a set of parameters appropriate for multiple domain key recovery is established. Three key recovery techniques are identified. It is shown that use of just one of these key recovery techniques is not sufficient for key recovery requirements among multiple domains. Further, it is shown that even key recovery systems using a combination of these techniques involve a complex tradeoff between cryptographic flexibility, system complexity and overall soundness. This forms a major technical difficulty in the search for a satisfactory system design.