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An inconvenient truth about tunneled authentications

In recent years, it has been a common practice to execute client authentications for network access inside a protective tunnel. Man-in-the-middle (MitM) attacks on such tunneled authentications have been discovered early on and cryptographic bindings are widely adopted to mitigate these attacks. In this paper, we shake the false sense of security given by these so-called protective tunnels by demonstrating that most tunneled authentications are still susceptible to MitM attacks despite the use of cryptographic bindings and other proposed countermeasures. Our results affect widely deployed protocols, such as EAP-FAST and PEAP.