Cryptographic Audit Infrastructure
QUORUM does not ask auditors to trust its records. Each decision is recorded before it is returned and sealed into a signed, hash-chained ledger, and QUORUM produces proofs that a third party can check with public keys and standard algorithms.
A decision is linked to the signed ledger in four steps. Each step can be checked on its own; together they show that a specific decision was recorded, when, and that it has not been changed since.
Verdict, score, flags, reference, time and a SHA-256 digest of the inputs — never the raw inputs — serialised canonically and hashed. If the record cannot be stored, no verdict is issued.
A sealer places each institution's new records under a Merkle root. An inclusion proof for one decision is a short list of SHA-256 hashes (O(log n)).
The batch root is appended to the audit ledger. Each entry carries the previous entry's hash and two signatures — Ed25519 and the post-quantum ML-DSA-65 (FIPS 204) — and both must verify. A scan every 15 minutes detects broken links or signatures and raises an alert; it never repairs or re-signs.
When a timestamp authority is configured, the ledger's Merkle root is timestamped every 100 entries. The authority receives only a hash. Tokens are verified against pinned authority root certificates.
Record → batch root → signed ledger entry → ledger root (→ timestamp), for any decision ID.
Merkle proof that a ledger entry is under a published root, checkable with SHA-256 alone.
A Bulletproofs range proof that a decision's score was within stated bounds, without revealing the score. Bound to the decision and its record hash and signed by QUORUM. No trusted setup.
The Ed25519 and ML-DSA-65 public keys needed to verify ledger entries and proofs offline.
From the institution's own QUORUM deployment. Archive the keys and anchored roots outside the database.
From the canonical decision record.
Hash up to the batch root, then confirm the root appears in the ledger entry.
Standard Ed25519 and ML-DSA-65 verification, plus the previous-entry hash.
Parse the RFC 3161 token and verify the authority's signature over the root hash.
The source repository includes a stand-alone verifier for Bulletproofs score proofs (scripts/verify-zk-proof.ts).
The ledger is stored in PostgreSQL. A privileged database user could alter it, but any change to an anchored entry is detectable without trusting QUORUM.
The proofs show a decision was recorded and not changed. They do not prove the rules were the right ones; that is a governance question.
Production signing keys are held in an AWS Nitro Enclave. This is implemented but not yet exercised on Nitro hardware. No independent cryptographic review has yet been performed.