VOIP or Voice Over Internet Protocol is a common term for phone service over IP based networks. There are much information about VoIP and some of how VoIP can be secured. There is however no standard for VoIP and no general solution for VoIP Security. The security in VoIP systems today are often non existing or in best case weak and often based on proprietary solutions. This master thesis investigates threats to VoIP system and describes existing alternatives for securing VoIP as it is today. Security requirements for VoIP system are identified and a new security solution is proposed that will increase the security in VoIP system. The proposed solution secures the SIP signaling in VoIP and focus on end to end security. The requirements on the new solution focus on confidentiality, integrity, availability and that the security solution is user friendly. We will here propose an zero effort security solution that easily can be used by non technical users. A fully function prototype of a secured SIP phone is developed to test if suggested design works as assumed.