The JSON representing the unsigned transaction.
Registry and metadata used for constructing the method.
// Serialized signing payload.
const signingPayload = createSigningPayload(unsigned, {
metadataRpc,
registry
});
// Construct an `ExtrinsicPayload` class. Careful, the `version` here is the
// `TRANSACTION_VERSION` format version, and **NOT** the
// `transaction_version` field from the `state_getRuntimeVersion` RPC
// endpoint.
const extrinsicPayload = registry
.createType('ExtrinsicPayload', unsigned, {
version: unsigned.version,
});
// With the `ExtrinsicPayload` class, construct the actual payload to sign.
// N.B. signing payloads > 256 bytes get hashed with blake2_256
// ref: https://github.com/paritytech/substrate/blob/master/primitives/runtime/src/generic/unchecked_extrinsic.rs#L171-L220
extrinsicPayloadU8a = extrinsicPayload.toU8a({ method: true })
const actualPayload = extrinsicPayloadU8a.length > 256
? registry.hash(extrinsicPayloadU8a)
: extrinsicPayloadU8a;
// You can now sign `actualPayload` with your private key.
// Note: you can use `u8ToHex` from @polkadot/util to convert `actualPayload`
// to a hex string.
// Alternatively, call the `.sign()` method directly on the
`ExtrinsicPayload` class.
const { signature } = extrinsicPayload.sign(myKeyPair);
Construct the signing payload from an unsigned transaction and export it to a remote signer (this is often called "detached signing").
Important! The registry needs to be passed into the
optionsargument. This registry needs to be updated with latest metadata, so before calling this function, make sure to runregistry.setMetadata(metadata)first.Important! The return value of this function is NOT the actual payload to sign: the actual payload to sign includes
methodwhich should not be length-prefixed. To construct the actual payload to sign, see the example.