The present document defines the security architecture of NGN. The present document addresses the security architecture required to fulfil the NGN security requirements defined in TS 187 001 [1] and includes the definition of security architectures to provide protection for each of the NGN functional architecture (ES 282 001 [2]) and its subsystems (NASS ES 282 004 [5]@ PES ES 282 002 [3]@ ES 282 007 [15]@ SIP and SDP call control ES 283 003 [14] and RACS ES 282 003 [4]). Where appropriate the present document endorses security mechanisms defined in other specifications. The present document addresses the security issues of the NGN core network and the NGN access network(s) and the Customer Premises network (CPN).