Future mobile systems are expected to offer users flexible access to information and services using a combination of different end-user devices in a Personal Distributed Environment (PDE). With PDEs able to operate over multiple air interfaces and heterogeneous networks, requiring seamless and rapid service provision, a flexible and fair trading of communication services is required. For this reason, a Digital Marketplace (DMP) is proposed. The DMP is based on an agent framework capable of

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... ing real-time service negotiation over disparate networks according to users' price and QoS requirements. This paper discusses the security threats and challenges to the PDE, and also to a DMP implementation.