FINGERTRAP: A Self-Defending Cryptographic Protocol for Network Communications

FINGERTRAP is a network encryption and authentication protocol that extends the X3DHand Double Ratchet frameworks with three novel mechanisms inspired by the Chinesefinger trap (zh˘ı w˘ang): a friction ratchet that exponentially increases computational costfor each failed authentication attempt; a recursive annihilation protocol that irreversiblydestroys all cryptographic state after a configurable failure threshold; and a committhen-challenge handshake that requires a counterintuitive “inward” action for legitimateauthentication. A bidirectional weave hash extends the Double Ratchet’s transcript bindingto cover every message in both directions. Together, these mechanisms provide permessageforward secrecy, post-compromise security (self-healing), clock-free operation,and a self-destruct capability. The individual ingredients-client puzzles, key erasure, andratcheting-each build on established lines of work; their combination into a single statefulprotocol, in which failed authentication attempts cryptographically tighten the sessionstate and ultimately destroy it, is not to our knowledge offered by deployed transportprotocols such as TLS 1.3, Signal, or WireGuard. The design targets deployments in whichinterception or capture of a device implies endpoint compromise, such as Unmanned AerialVehicle (UAV) telemetry links and body-worn sensors, where denial of exploitation requiresguaranteed loss of past and future session material. We describe the full protocol, providegame-based security arguments under an explicit adversarial model, give analytic costestimates for the friction mechanism, analyse the denial-of-service surface and a two-layermitigation strategy, and specify a post-quantum extension using hybrid X25519/ML-KEM-768 ratcheting.