VA-DAR: A PQC-Ready, Vendor-Agnostic Deterministic Artifact Resolution for Serverless, Enumeration-Resistant Wallet Recovery

Abstract: Serverless wallet recovery must balance portability, usability, and privacy. Public registries enable decentralized lookup but naive identifier hashing leaks membership through enumeration. We present VA-DAR, a keyed-discovery protocol for ACE-GF-based wallets that use device-bound passkeys for day-to-day local unlock while supporting cross-device recovery using only a user-provided identifier (e.g., email) and a single recovery passphrase. As a discovery-and-recovery layer over ACE-GF, VA-DAR inherits ACE-GF's context-isolated, algorithm-agile derivation substrate, enabling non-disruptive migration to post-quantum algorithms at the identity layer. The design introduces a decentralized discovery-and-recovery layer that maps a privacy-preserving discovery identifier to an immutable content identifier of a backup sealed artifact stored on a decentralized storage network. Concretely, a user derives passphrase-rooted key material with a memory-hard KDF, domain-separates keys for artifact sealing and discovery indexing, and publishes a registry record keyed by a passphrase-derived discovery identifier. VA-DAR provides: (i) practical cross-device recovery using only identifier and passphrase, (ii) computational resistance to public-directory enumeration, (iii) integrity of discovery mappings via owner authorization, and (iv) rollback/tamper detection via monotonic versioning and artifact commitments. We define three sealed artifact roles, two update-authorization options, and three protocol flows (registration, recovery, update). We formalize security goals via cryptographic games and prove, under standard assumptions, that VA-DAR meets these goals while remaining vendor-agnostic and chain-agnostic. End-to-end post-quantum deployment additionally requires a PQ-secure instantiation of registry authorization.