Core concepts

Three capabilities, in the order you will use them. Each one stands on the one before it, so a device can stop at identity, add signed data, or go all the way to payments.

Device identity#

On first boot the device generates two keypairs and persists them through the platform layer:

• Ed25519 signs attestations — fast, compact, chain-neutral.
• secp256k1 signs payment authorizations and supports ecrecover, so an EVM settlement service can tell which device signed.

From them the device derives a did:mw:… identifier and an EVM address. The keys are not exported, not derived from a server secret, and not shared between the two sides of a payment. A device that loses its storage loses its identity — that is the intended trade.

boat_keypair_t kp;
boat_crypto_init(&kp);        /* load, or generate and persist */
printf("%s\n%s\n", kp.did, kp.eth_addr_hex);

Verifiable machine data#

An attestation is a SHA-256 hash of a reading, signed with the device's Ed25519 key. A third party holding the payload and the public key can check later that this device said this, unaltered.

boat_attestation_t att;
boat_attest_create(&kp, "{\"kwh\":0.417,\"t\":1756713600}", &att);

Unpaid attestation carries no chain binding. The paid submission path (boat_attest_submit_paid) speaks x402 against an eip155:<chain_id> network.

Machine payments#

A payment authorization is an EIP-3009 transfer authorization over EIP-712 typed data, signed on the device. The device signs; it does not submit. A settlement service verifies the signature and carries it on-chain, often many at once.

boat_nano_auth_t auth;        /* 417 micro-USDC */
boat_nano_sign(&kp, payee, 417u, chain_id, verifier,
               "GatewayWalletBatched", "1", NULL, &auth);

uint8_t recovered[20];        /* what settlement does */
boat_nano_verify(&auth, chain_id, verifier,
                 "GatewayWalletBatched", "1", recovered);

The EIP-712 domain binds a signature to one chain and one verifying contract. Presented anywhere else, it does not verify — which is why the Quick Start ends with cross-chain correctly rejected.

Layers and headers#