Replay Attack in TLS 1.3 0-RTT Handshake: Countermeasure Techniques

Transport Layer Security (TLS) is an Internet Engineering Task Force (IETF) standard protocol commonly used on the Internet nowadays. TLS 1.3 the latest version published in August 2018 introduced a new mode to perform the handshake in zero round-trip time (0-RTT) which led to a significant improvement in the protocol performance. 0-RTT handshake mode allows the client to establish the connection and send the application data in the first message (ClientHello) without waiting for the server to send a response. But it also opens a window for replay attacks. The attack occurs when a valid 0-RTT handshake message is captured and sent again to the server causing the server to perform the same process again according to the application data carried in the message. Several anti-replay protection techniques were introduced to prevent or mitigate the replay attack. This paper sheds light on replay attacks countermeasures for TLS 1.3 0-RTT handshake mode and the most recent proposed methods. The strength and limitations of these countermeasures are discussed. In addition, the paper deliberates on the challenges such countermeasures impose in a distributed environment, for instance, multiple servers in a cloud computing environment or a content delivery network (CDN).