Paper 2026/1472

Vordr: Verifiable, Scalable and Anonymous Remote Attestation for Confidential Virtual Machines

Abstract

Confidential virtual machines (CVMs) provide hardware-rooted attestation and isolation, protecting data in use from untrusted cloud infrastructure. However, current CVM attestation frameworks are limited to a two-party trust model between the cloud provider and the CVM owner, and primarily guarantee only the boot-time state. As CVMs increasingly host public-facing workloads (e.g., LLM inference APIs, web applications) that process end-user data, this creates a three-party trust mismatch among the cloud provider, the CVM owner, and end users. Once a workload is deployed, end-users lack cryptographic assurance of runtime integrity and must implicitly trust the CVM owner for any post-launch modifications. Furthermore, extending continuous runtime attestation to a large number of end users introduces severe scalability bottlenecks and is vulnerable to co-location-based attacks. Existing methods either enforce static post-launch lockdown or rely on CVM owner-maintained software logs that are not hardware-anchored. We present Vordr, a framework that removes the CVM owners from the end-user's trust domain across the full CVM lifecycle while still allowing workload-level updates/installations with auditability. We introduce a novel architecture that establishes an exclusive administrative binding between a process-based TEE (Warden Enclave (WEN)) and the CVM. This binding strictly blocks the CVM owners (or cloud) from directly manipulating the CVM. Vordr continuously tracks runtime integrity via a hardware-rooted Linux IMA event log anchored to PCR 10, serving time-bounded, platform-unlinkable cached or audit-ready quotes for independent end-user auditing. We optimize the costly IMA-log extraction via a novel incremental attestation design leveraging the IMA log's append-only structure and the WEN's sealed state. We implement Vordr, validate it across several workloads, and show that it provides up to 60.8x speedup for runtime monitoring with huge communication reductions in steady-state incremental rounds compared to prior methods. Vordr delivers highly scalable and verifiable runtime attestation, providing substantially stronger guarantees for runtime integrity and platform unlinkability.

Note: Rejected from ACM CCS 2026.