Abstract
In this paper we present a key escrow system which meets possible requirements for international key escrow, where different domains may not trust each other. In this system multiple third parties, who are trusted collectively but not individually, perform the dual role of providing users with key management services and providing authorised agencies in the relevant domains with warranted access to the users' communications. We propose two escrowed key agreement mechanisms, both designed for the case where the pair of communicating users are in different domains, in which the pair of users and all the third parties jointly generate a cryptographic key for end-to-end encryption. The fact that all entities are involved in the key generation process helps make it more difficult for deviant users to subvert the escrowed key by using a hidden ‘shadow-key’. The first mechanism makes use of a single set of key escrow agencies moderately trusted by mutually mistrusting domains. ! The second mechanism uses a transferable and verifiable secret sharing scheme to transfer key shares between two groups of key escrow agencies, where one group is in each domain.