Bare PC SIP User Agent Implementation and Performance for Secure VoIP

Bare PC systems, which run applications without using any operating system (OS) or kernel, are immune to attacks targeting a specific OS. They also perform better than conventional systems due to their reduced overhead. We describe the design, implementation and performance of a SIP user agent (UA) for secure VoIP on a bare PC system. In particular, we discuss SIP functions and message handling, and CPU tasking. We also give details of the UA design and code that enable a lean implementation of SIP to be intertwined with the network protocols needed for secure VoIP on a bare PC softphone. The interoperability of the bare PC SIP UA is verified by conducting tests using OS-based as well as bare PC SIP servers and UAs. We also study bare PC SIP UA performance by comparing timings for key SIP UA operations for the bare PC softphone with timings for a compatible Linux softphone. The results show that processing times for the SIP register and invite operations for the bare PC SIP softphone are significantly less than the corresponding times for the Linux softphone regardless of whether a bare PC or a Linux-based SIP server is used. Finally, we propose a simple security extension to SIP authentication that enables the session key exchange for media protection to be encrypted without incurring the overhead of TLS or IPsec. Bare PC SIP softphones can be used for building secure and efficient VoIP systems that do not require any OS support. Keywords-bare PC; SIP implementation; SIP performance; SIP user agent; VoIP; VoIP security.