The present document defines the security requirements pertaining to TISPAN NGN Release 3. The present document holds requirements for the various NGN subsystems defined at a stage 1 level. The present document covers security requirements for both the NGN core network@ and the NGN access network(s). The main scope of the security requirements for the different subsystems are to identify requirements in the following main areas: ? Security Policies. ? Authentication@ Authorization@ Access Control and Accountability. ? Identity and Secure Registration. ? Communications and Data Security Requirements (including confidentiality@ integrity aspects). ? Privacy. ?Key Management. ? NAT/Firewall Interworking. ? Availability and DoS protection. ? Assurance. ? Strength of Security Mechanisms.