Catching the Cuckoo: Verifying TPM Proximity Using a Quote Timing Side-Channel

Abstract

We present a Trusted Platform Module (TPM) application protocol that detects a certain man in the middle attack where an adversary captures and replaces a legitimate computing platform with an imposter that forwards platform authentication challenges to the captive over a high speed data link. This revised Cuckoo attack allows the imposter to satisfy a user's query of platform integrity, tricking the user into divulging sensitive information to the imposter. Our protocol uses an ordinary smart card to verify the platform boot integrity through TPM quote requests, and to verify TPM proximity by measuring TPM tickstamp times required to answer the quotes. Quotes not answered in an expected amount of time may indicate the presence of an imposter's data link, revealing the Cuckoo attack. We describe a timing model for the Cuckoo attack, and summarize experimental results that demonstrate the feasibility of using timing to detect the Cuckoo attack over practical levels of adversary link speeds.