Voice Over IP : Unsafe at any Bandwidth ?

Voice over IP (VoIP) is promising a silver bullet for future voice services. There are several technical aspects which make the technology attractive; it is in particular believed to reduce operating costs and increase flexibility by converging networks. This paper offers a technical analysis of the security aspects of VoIP; we discuss the major differences and implications of VoIP, in particular compared to circuit-switched voice as it is deployed today by network operators. We will concentrate on the “signalling” part of VoIP, based on the Session Initiation Protocol (SIP). Our analysis considers primarily consumer scenarios, rather than VoIP deployment by/for business customers.