Paper 2026/2679

Cryptanalysis and Enhancement of VTBSAE: Provably Secure Verifier-Based PAKE Protocols for the Industrial Internet of Things

Abstract

Verifier‑based password‑authenticated key exchange (PAKE) enables a client and a server to establish high‑entropy session keys from low‑entropy passwords without requiring the server to store plaintext passwords. This asymmetric design reduces the risk that leakage of server‑side credentials directly leads to client impersonation, making verifier‑based PAKE well suited to authentication and session‑key establishment for Industrial Internet of Things (IIoT) devices. In this paper, we analyze the recently proposed VTBSAE, a verifier‑based PAKE protocol, and reveal that it fails to provide the claimed resistance against server‑compromise client‑impersonation attacks. To fix this vulnerability, we propose E‑VTBSAEv1. While preserving the lightweight structure of VTBSAE, E‑VTBSAEv1 binds the client‑generated point \(E_{1}\) to fresh server‑side randomness. We also briefly discuss E‑VTBSAEv2 as a challenge‑based variant. We provide a formal security proof for E‑VTBSAEv1 in the random‑oracle model under the CDH assumption, covering AKE security, forward secrecy, and resistance to server‑compromise client‑impersonation attacks after server‑side verifier‑file leakage. We evaluate E‑VTBSAEv1 under two practical deployment settings: a Raspberry Pi 4B server with an AutoDL client, and a Raspberry Pi 4B server with a Raspberry Pi 4B client. The experimental results show that E‑VTBSAEv1 preserves the communication and storage overheads of VTBSAE and achieves runtime performance comparable to that of VTBSAE.