Lawful Interception in P2P-Based VoIP Systems

Lawful Interception of Voice-over-IP communications is technically more challenging than Lawful Interception in the PSTN. Currently, Lawful Interception for Voice-over-IP traffic is being standardised with respect to VoIP service architectures where central entities are on the signalling path, as this is the way VoIP is being deployed today. However, future types of VoIP service architectures may be characterised by a higher degree of decentralisation. In the extreme case, there is no central entity in the network through which signalling will pass. As an example for such a highly decentralised VoIP system, several proposals have suggested to use a P2P-network for VoIP signalling in conjunction with the Session Initiation Protocol (SIP), commonly referred to as P2PSIP. This paradigm change to P2P-based signalling has significant implications for authorised interception of communications. In this paper, we analyse the problem of applying Lawful Interception to P2P-based Voice-over-IP systems technically, highlighting the characteristic properties of such an approach and the corresponding implications that complicate Lawful Interception. Further, we inspect potential solutions for implementing Lawful Interception in a P2PSIP system in general and discuss advantages and drawbacks of such solutions.