Paper 2026/1749 Original: eprint.iacr.org/2026/1749 ↗

CAKE-HI - Compact Authenticated Key Exchange Hiding Identities

Abstract

Modern public-key cryptography is threatened by advances in quantum computing. As a result, there has been a shift towards cryptographic algorithms that can resist attacks by a quantum computer. However, these algorithms use significantly longer keys, and produce larger ciphertexts and digital signatures than their classical counterparts. These bigger sizes pose problems for devices that are bandwidth- and/or power-limited, and wish to establish a secure, quantum resistant communication channel with another device. In order to reduce the overhead of using these algorithms in challenging environments while maintaining security posture, we present Compact Authenticated Key Exchange – Hiding Identities (CAKE-HI). To evaluate our protocol, we compare the key exchange handshake size and computational efficiency of mutual authenticated TLS and CAKE-HI. Measurements show that CAKE-HI significantly reduces the handshake size and the computational overhead of establishing a quantum-secure link. In addition, we formalize and prove security properties about CAKE-HI in the symbolic and computational model using the protocol analysis frameworks Verifpal and CryptoVerif.