Practical authentication in large-scale Internet applications

Internet applications have experienced a rapid and massive growth in popularity in the last decade. For example, today many Web and Voice over IP (VoIP) applications rely on large and highly-distributed infrastructures to process requests from millions of users in a timely manner. Due to their unprecedented requirements, these large-scale Internet applications have often sacrificed security for other goals such as performance, scalability and availability. As a result, these applications have typically preferred weaker but more efficient security mechanisms in their infrastructures.;Authentication mechanisms, a security layer required by most Internet applications, are an example of this trend. Mechanisms such as Digest authentication, HTTP Cookies, HTML form-based authentication and SSL/TLS server authentication are widely deployed regardless of their known weaknesses. However, as recent incidents have demonstrated, due to the increasing importance of large-scale Internet applications, powerful adversaries are now targeting and exploiting the weaknesses in these authentication mechanisms. While more robust authentication mechanisms have been proposed, most of them fail to address the specific requirements and threat model of large-scale Internet applications and, as a result, they have not been widely deployed.;In this dissertation we demonstrate that by taking into account the specific requirements and threat model of large-scale Internet applications we can design authentication protocols for such applications that are not only more robust but also have low impact on performance, scalability and existing infrastructure. In particular, we show that there is no inherent conflict between stronger authentication and other system goals.;This dissertation makes four major contributions. First, through an extensive experimental study, we demonstrate how even a simple authentication mechanism such as SIP Digest authentication can significantly impact the performance and scalability of a carrier-scale VoIP infrastructure. Second, we propose Proxychain, a SIP authentication protocol that not only provides better security guarantees than Digest authentication but also improved performance and scalability for highly-distributed VoIP environments. Third, we develop One-Time Cookies (OTC), a more secure alternative to the use of HTTP cookies as session authentication tokens. OTC is inherently robust against session hijacking attacks while preserving the efficiency and statelessness benefits of cookies. Fourth, we present Direct Validation of SSL/TLS Certificates (DVCert), a practical mechanism that offers more robust validation of SSL/TLS server certificates without requiring external third-parties or additional infrastructure. By providing stronger server authentication, DVCert effectively reduces the risk of man-in-the-middle attacks against SSL/TLS connections. In so doing, we provide robust and practical authentication mechanisms that can improve the overall security of large-scale VoIP and Web applications.