Canton MPC PoC

MPC-based ERC-20 custody on Canton. Daml smart contracts manage vault state (deposits, withdrawals, holdings); a TypeScript MPC service signs EVM transactions using threshold-derived keys via signet.js; the Canton ledger verifies every MPC signature on-chain via secp256k1WithEcdsaOnly before crediting or debiting holdings.

Where to start

You are…	Read
Integrating the Signer into a new Daml domain	daml-packages/daml-signer/README.md — authority model, lifecycle, full API
Using the ERC-20 Vault (deposit / claim / withdraw / refund)	daml-packages/daml-vault/README.md — templates, choices, calldata shape, security invariants
Building a TypeScript client / 3rd-party integration	ts-packages/canton-sig/README.md — CantonClient + crypto + EVM tx helpers
Reproducing requestId cross-language	daml-packages/daml-eip712/README.md — primitive encoders + composition rule
Decoding ABI return data on-ledger	daml-packages/daml-abi/README.md — slot vs byte-offset addressing
Running a full multi-participant Canton stack	SETUP.md — local CN Quickstart (Keycloak, Splice, observability)

For executable end-to-end flows: test/src/test/sepolia-e2e.test.ts (deposit) and test/src/test/sepolia-withdrawal-e2e.test.ts (withdrawal + refund). The shared test/src/test/helpers/e2e-setup.ts is the canonical worked example of disclosed-contract wiring, RequestDeposit arguments, signed-tx broadcast, and ClaimDeposit.

Architecture in one paragraph

The Signer is a singleton signed by the MPC party (sigNetwork) and disclosed to consumer contracts. A consumer choice creates a transient SignRequest (signed by operators + requester) and immediately exercises Signer.SignBidirectional, which derives the operator-set fingerprint on-chain (sender = operatorsHash) and emits a SignBidirectionalEvent for the MPC to watch. The consumer stores that event CID on its single-use pending anchor. The MPC derives a child secp256k1 key from the root key using KDF inputs sender = operatorsHash and the request path, threshold-signs the EVM transaction, and publishes the signature in SignatureRespondedEvent. The consumer (or test/client) reads that signature, reconstructs the signed EIP-1559 tx, and submits it to the destination chain via eth_sendRawTransaction. Once the receipt is observable, the MPC re-simulates the call to extract the ABI-encoded return data and publishes a RespondBidirectionalEvent whose signature (made with the response-verification child key derived with sender = operatorsHash and path = "canton response key" over keccak256(requestId ‖ serializedOutput)) is verified on-ledger by the consumer's claim choice via secp256k1WithEcdsaOnly. After validated claim/completion, the consumer archives the pending anchor, both response evidence contracts, and the original SignBidirectionalEvent. The daml-vault package is one consumer of this protocol; ERC-20 holdings, deposit anchors, and refund-on-failure withdrawal are domain logic on top of the generic Signer.

Per-package details live in the documents listed under Where to start. Earlier design notes under proposals/ describe pre-current iterations and may not reflect the shipped code.

Prerequisites

Tool	Version	Install
Java	21+	Temurin
Daml SDK (DPM)	3.4.11	curl -sSL https://get.digitalasset.com/install/install.sh | sh
Node.js	24+	nodejs.org
pnpm	10+	corepack enable && corepack prepare pnpm@latest --activate

After installing DPM, make sure ~/.dpm/bin is on your PATH. To point at a non-default sandbox, set CANTON_JSON_API_URL in test/.env (defaults to http://localhost:7575); see test/.env.example for all variables.

Quick Start

1. Build the DAR and generate codegen

dpm build --all
cd test
pnpm run codegen:daml
pnpm install

2. Start the Canton sandbox

In a separate terminal (keep it running):

cd test
pnpm daml:sandbox

Wait until you see the JSON API listening on port 7575. You can verify with:

curl -sf http://localhost:7575/docs/openapi > /dev/null && echo "Ready"

3. Run tests

cd test
pnpm test          # single run of the test/ Vitest suite

After Daml source changes: cd test && pnpm generate (clean + DAR + codegen + install; needs the sandbox up for OpenAPI codegen).

Daml Unit Tests

These don't need the sandbox:

dpm build --all
for pkg in daml-abi daml-uint256 daml-eip712 daml-signer daml-vault; do
  (cd daml-packages/$pkg && dpm test)
done

dpm test does not support --all — each package must be tested individually.

TypeScript Package Tests

These don't need the sandbox:

pnpm -r --filter='@canton/*' --filter='canton-sig' run test

Sepolia E2E Tests

End-to-end tests that exercise the full deposit/withdrawal lifecycle against a live Sepolia RPC and the Canton sandbox.

Setup

cd test
cp .env.example .env

Fill in the required values:

Variable	Description
CANTON_JSON_API_URL	(optional) Canton JSON API base URL (default http://localhost:7575)
SEPOLIA_RPC_URL	Sepolia JSON-RPC endpoint (Infura, Alchemy, etc.)
MPC_ROOT_PRIVATE_KEY	0x-prefixed secp256k1 private key (64 hex chars)
MPC_ROOT_PUBLIC_KEY	Uncompressed SEC1 public key (04 + x + y, no 0x prefix)
VAULT_ID	Vault discriminator for MPC key derivation
FAUCET_PRIVATE_KEY	(optional) Defaults to MPC_ROOT_PRIVATE_KEY
ERC20_ADDRESS	(optional) Defaults to test USDC on Sepolia

Fund the faucet

pnpm sepolia:preflight    # prints faucet address + current balances

Send to the faucet address:

• ~0.002 ETH for gas per test run
• ERC-20 tokens for the deposit amount

Run

# Start sandbox in a separate terminal first, then:
pnpm test          # runs the test/ Vitest suite, including Sepolia e2e when env is set

Available Scripts

From test/:

Script	Description
pnpm test	Run the test/ Vitest suite; Sepolia e2e runs if env is set
pnpm daml:build	Build the DAR
pnpm daml:test	Run Daml Script tests
pnpm daml:sandbox	Start Canton sandbox with JSON API on :7575
pnpm codegen:daml	Regenerate Daml JS codegen from built DAR
pnpm codegen:api	Regenerate OpenAPI types (requires running sandbox)
pnpm generate	Full clean rebuild: DAR + codegen + install
pnpm sepolia:preflight	Check faucet balances and print deposit addresses

From root:

Script	Description
pnpm check	Typecheck + lint + knip + format check
pnpm fix	Auto-fix lint + format