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Polkadot-API

Raw TxCreator

PAPI provides a helper to build a TxCreator directly from a raw signing function, provided by a cryptographic library, a hardware wallet, etc. It deals with the chain transaction side and leaves the cryptographic signature part to the consumer.

getTxCreator

It is a function to get a TxCreator.

Returns

TxCreator

Parameters

publicKey

Type: Uint8Array

Public key or account identifier used to identify the account.

signingType

Type: "Ecdsa" | "Ed25519" | "Sr25519"

Signature schema used to sign.

sign

Type: (input: Uint8Array) => Promise<Uint8Array> | Uint8Array

Cryptographic signature function, signing with the signingType previously declared.

Examples

In these examples we use several libraries:

Some snippets might work in other versions.

Ed25519

import {  } from "polkadot-api/tx-creator"
import {  } from "@noble/curves/ed25519.js"
 
const  = new () // get your key
 
const  = (
  .(),
  "Ed25519",
  () => .(, ),
)

Sr25519

From private key

import {  } from "polkadot-api/tx-creator"
import * as  from "@scure/sr25519"
 
const  = new () // get your key
 
const  = (
  .(),
  "Sr25519",
  () => .(, ),
)

From mnemonic phrase

This snippet helps to create a TxCreator for Alice, Bob, Charlie, etc.

You can replace by your own mnemonic phrase.

import {  } from "@polkadot-labs/hdkd"
import {
  ,
  ,
  ,
} from "@polkadot-labs/hdkd-helpers"
import {  } from "polkadot-api/tx-creator"
 
const  = (())
const  = ()
const  = ("//Alice") // or `//Bob`, `//Charlie`, etc
 
const  = (
  .,
  "Sr25519",
  .,
)

Ecdsa

Ecdsa is an umbrella term for two types of TxCreators using ECDSA signatures over Secpk1. In a glance, these are the two types:

  • EVM-like chains (Moonbeam, Mythos, Darwinia, Crab, etc.) expect the signer to sign payloads using a Keccak256 hash and use AccountId20 addresses (Ethereum-like addresses).
  • Polkadot-like chains (e.g., Polkadot, Kusama) expect the signer to sign payloads using Blake2_256 and use AccountId32 addresses (Polkadot-like addresses).

With that distinction in mind, here's how you can create Ecdsa TxCreators for these different chain types:

Polkadot-like chains

import {  } from "@noble/curves/secp256k1.js"
import {  } from "@noble/hashes/blake2.js"
import {  } from "polkadot-api/tx-creator"
 
const  = new () // get your key
 
const  = (
  (.(), { : 32 }),
  "Ecdsa",
  () => {
    const  = .((, { : 32 }), , {
      : false,
      : "recovered",
    })
    return .([....(1), [0]])
  },
)

Ethereum-like chains

import {  } from "@noble/curves/secp256k1.js"
import {  } from "@noble/hashes/sha3.js"
import {  } from "polkadot-api/tx-creator"
 
const  = new () // get your key
 
const  = (
  (.(, false).(1)).(-20),
  "Ecdsa",
  () => {
    const  = .((), , {
      : false,
      : "recovered",
    })
    return .([....(1), [0]])
  },
)
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