Voice Over Internet Protocol and Skype Security

Open Society Institute
Simson L. Garfinkel [Download full article] [Russian]

With the increased deployment of high-speed ("broadband") Internet connectivity, a growing number of businesses and individuals are using the Internet for voice telephony, a technique known as Voice over Internet Protocol (VoIP). With a VoIP system, two people can speak with each other by using headsets and microphones connected directly to their computers.

Skype is a proprietary VoIP system developed by Skype Technologies S.A. Like the popular KaZaA file-trading system, Skype is based on peer-to-peer technology: instead of transmitting all voice calls through a central server, as some VoIP services do (Vonage, for example), Skype clients seek out and find other Skype clients, then build from these connections a network that can be used to search for other users and send them messages.

Is Skype secure? How does its security compare with that of conventional telephone calls, or of other VoIP-based systems? In this article commissioned by OSI's Information Program, Simson Garfinkel, an expert on Internet security and networking issues, looks at the security properties of key importance for civil society organizations relying on Skype for voice communications.

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