This European Telecommunication Standard (ETS) provides a description of the additional requirements, features and mechanisms necessary to provide adequate security within the UPT service for Phase 2. It is based on the specification of the Security Architecture for UPT Phase 1, given in ETS 300 391-1 [2] and it specifies the additions to Phase 1 only. The specific security requirements, features and mechanisms additionally needed for UPT Phase 2 are specified in detail. Where applicable Phase 1 is referred to. Downwards compatibility to UPT Phase 1 is fulfilled. Both this ETS and ETS 300 391-1 [2] are based on the general UPT security architecture given in