auths-transparency

Append-only transparency-log primitives for Auths: RFC 6962 Merkle math, C2SP-style checkpoints and witness cosignatures, tile storage, offline-bundle verification, and the witness-diversity (independence) gate.

This is the CT-checkpoint half of Auths' two witness subsystems. (The other is the KERI-rct key-event receipting layer in auths-core::witness / auths-keri::witness — a separate protocol with separate keys. Don't conflate them.)

What's in it

• merkle — RFC 6962 leaf/node hashing, inclusion proofs (verify_inclusion), and consistency proofs (verify_consistency) between two tree sizes. Pure, no-I/O, WASM-safe.
• checkpoint — Checkpoint (origin/size/root/timestamp), its C2SP signed-note body, SignedCheckpoint (log signature + Ed25519 or ECDSA-P256), and WitnessCosignature.
• tile / store — C2SP static tile layout + TileStore (filesystem, and S3 under the s3 feature) for serving a log.
• bundle / verify — OfflineBundle + verify_bundle: a synchronous, I/O-free verification of signature, inclusion, checkpoint, witness quorum, and namespace against a pinned TrustRoot. This is the embeddable verifier path.
• witness (native feature) — the C2SP tlog-witness cosignature protocol types (CosignRequest/CosignResponse, cosignature_signed_message).
• witness_policy — a typed, fail-closed loader for data/witness_policy.json (the runtime diversity policy). Rejects a missing file, unparseable JSON, unknown schema version, or a placeholder pubkey_b64.
• Independence gate — verify_bundle's witness check layers auths_keri::witness::independence::spans_distinct (distinct organizations / jurisdictions / infrastructure) on top of the n/2+1 count, evaluated over the actual cosigning quorum. A count-met-but-correlated quorum returns WitnessStatus::NotIndependent.

The runtime data/witness_policy.json (who is trusted to cosign now) is deliberately separate from the governance docs/governance/admission_policy.json (who may become a witness). Neither may be weakened to make a verify pass.

How it fits in the architecture

auths-sdk / auths-cli / auths-monitor / auths-checkpoint-cosigner
  |
  +-- auths-transparency (THIS CRATE)
        |
        +-- depends on: auths-verifier (types, Ed25519/ECDSA), auths-crypto,
        |               auths-keri (the shared independence model)
        +-- default-features=false → WASM-safe verify path (no ring/tokio)
        +-- "native" feature → tile stores, witness cosigner protocol, async

Dependency direction: depends downward on auths-verifier/auths-crypto/ auths-keri; nothing in those depends back on it. The verify path is designed for minimal-dependency embedding (FFI/WASM), so it stays free of ring/tokio unless native is enabled.

Usage

use auths_transparency::{verify_bundle, OfflineBundle, TrustRoot};

// Offline, I/O-free verification against a pinned trust root.
let report = verify_bundle(&bundle, &trust_root, now);
assert!(report.is_valid());

// Consistency between two checkpoints of the same log.
use auths_transparency::verify_consistency;
verify_consistency(old_size, new_size, old_root, new_root, &proof)?;

// Load the runtime witness-diversity policy (fail-closed).
use auths_transparency::WitnessPolicy;
let policy = WitnessPolicy::load(std::path::Path::new("data/witness_policy.json"))?;

Consumers: auths-sdk (bundle verification workflows), auths-monitor (cross-operator consistency), auths-checkpoint-cosigner (the cosigner), and the verifier embeddings.