The present document defines the security requirements pertaining to TISPAN NGN Release 1. 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 requirement 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.