A PKI-free Key Agreement Protocol for P2P VoIP Applications

The security of the protocols involved in peer-to-peer communications is becoming a fundamental prerequisite for their widespread diffusion. In this paper, we propose a new protocol for establishing a security association between two peers willing to set up a VoIP or multimedia communication through the standard SIP protocol. Our proposal is based on the MIKEY protocol and the Diffie-Hellman algorithm for key establishment, in a ZRTP like way. Beside this shared-secret-free method, we allow also the authentication via peer certificates without using any centralized PKI. An opportune distributed certificate management is also described. The proposed method has been also implemented and integrated in an open source SIP UA.