Tutorial 7 — Connect an App Proof to Cardano

Imported page

This page is generated from docs/appchain/tutorials/07-anchors-and-verification.md in the Yano X repository, which is its source of truth.

Open an evidence chain in App-Chain Studio

• Level: intermediate to advanced
• Time: about 20 minutes on local devnet
• Outcome: bootstrap a threshold-enforced script anchor, advance it after app blocks finalize, and understand the independent verification chain.

An app-chain finality certificate proves that the configured member threshold approved a block. An L1 anchor makes a later application position durable and discoverable through Cardano. These are related but distinct proofs.

1. Start an anchored local cluster

export YANO_CLUSTER_DIR=/tmp/yano-tutorial-anchor

./yano.sh appchain cluster start 3 \
  --anchor-mode script \
  --anchor-every 2

Script mode uses a thread NFT and a Plutus V3 validator. The local launcher has a deterministic demo anchor seed and can fund it from the self-contained devnet faucet.

2. Bootstrap one chain’s immutable anchor identity

./yano.sh appchain cluster anchor-bootstrap orders-chain

Bootstrap consumes a seed UTxO, mints the one-shot thread NFT, and creates the genesis datum. It establishes identity; it does not let the wallet alone claim an arbitrary application tip.

Inspect the L1 Anchor card on http://127.0.0.1:7070/ui/app-chain/. It should show the thread policy, script address, wallet, anchored height, transaction, and lag.

3. Produce application progress

./yano.sh appchain cluster submit orders-chain audit '{"event":"certificate-issued","id":"C-1"}'
./yano.sh appchain cluster submit orders-chain audit '{"event":"certificate-published","id":"C-1"}'
./yano.sh appchain cluster submit orders-chain audit '{"event":"certificate-acknowledged","id":"C-1"}'

Wait for app finality and the local L1 transaction:

sleep 20
./yano.sh appchain cluster status

curl -s \
  http://127.0.0.1:7070/api/v1/app-chain/chains/orders-chain/status \
  | jq .anchor

All members independently reconcile the authenticated script UTxO from their own L1 view. Node-local “confirmed since restart” counters may differ after a restart; the durable anchored height, transaction, and lag should converge.

4. The independent verification chain

For one application record, a verifier needs:

record/value
   │ MPF or messages-root proof
   ▼
state root / certified app block
   │ threshold finality certificate + block hash chain
   ▼
anchored descendant
   │ exact thread NFT + validator address + inline datum
   ▼
Cardano transaction confirmed by an independent L1 source

The checks are:

1. Recompute the record/message commitment.
2. Verify its MPF or messages-root path against the correct app-block root.
3. Verify the app block’s threshold signatures using an independently trusted chain profile.
4. When the record predates the anchor, verify the certified block-hash chain to the anchored descendant.
5. Fetch the Cardano transaction/UTxO independently.
6. Require the expected validator address and state-thread asset.
7. Decode the exact inline datum and match chain id, height, block hash, state root, member set, and threshold.

A transaction hash appearing in a Yano JSON response is not, by itself, independent anchor verification.

Metadata versus script anchoring

Property	Metadata	Script
Setup	Fund wallet	Fund wallet + bootstrap
L1 enforcement	Data commitment only	Monotonic thread + threshold member signatures
Main safety authority	Anchor wallet	On-chain validator and member threshold
Typical use	Low-cost timestamp/discovery	Strong consortium settlement boundary

Both modes commit application data; only script mode enforces the threshold and monotonic successor rules on chain.

Public test networks

For preview or preprod:

• generate a dedicated raw 32-byte anchor seed;
• provide it through the owner-only anchor-key file mechanism;
• fund the printed enterprise address with test ADA;
• use an explicit public-network confirmation before the demo spends; and
• increase cadence/stability settings to match real L1 timing and fees.

Do not reuse a wallet mnemonic, validator member seed, actor signing key, or API key as the anchor wallet.

5. Clean up

./yano.sh appchain cluster clean
unset YANO_CLUSTER_DIR

Local devnet state is disposable. A public script anchor is permanent Cardano history even after local files are deleted.

Go deeper

• Follow L1 anchoring §5 for portable evidence bundles and exact trust-context construction.
• Use EvidenceVerifier and EffectProofVerifier rather than trusting server booleans.
• Test L1 rollback and anchor resubmission before a pilot.
• Review the pinned Aiken release artifacts and the Java/julc cross-implementation drift checks before depending on a released script identity.