Paper 2021/627 Original: eprint.iacr.org/2021/627 ↗

VeRSA: Verifiable Registries with Efficient Client Audits from RSA Authenticated Dictionaries

Abstract

Verifiable registries allow clients to securely access a key-value mapping maintained by an untrusted server. Registries must be audited to ensure global invariants are preserved, which, in turn, allows for efficient monitoring of individual registry entries by their owners. To this end, existing proposals either assume trusted third-party auditors or rely on incrementally verifiable computation (IVC) via expensive recursive SNARKs to make registries client-auditable. In this work, we give new client-auditable verifiable registries with throughputs up to $100\times$ greater than baseline IVC solutions. Our approach relies on an authenticated dictionary based on RSA accumulators for which we develop a new constant-size invariant proof. We use this as a replacement for Merkle trees to optimize the baseline IVC approach, but also provide a novel construction which dispenses with SNARKs entirely. This latter solution adopts a new checkpointing method to ensure client view consistency.