# Polkadot Parachain

## Sign Transaction

The D'CENT Web SDK provides functions for signing transaction of coins.

### getParachainSignedTransaction**()**

#### Supported Coin Type

* Parachain - Astar(ASTR)
* Parachain Asset- Astar Asset(XC20)

#### Parameters 

* unsignedTx: unsigned hexadecimal tx [Polkadot Docs](https://wiki.polkadot.network/docs/build-transaction-construction)
* path: key path, wallet sign with that private key with a given key path (BIP32 ex) "m/44'/810'/0'/0/0").
* fee: fee, It is fee that wallet displays on the screen.
* symbol: symbol, It is a symbol that the wallet displays on the screen.
* decimals: Parachain's decimals.
* RPCUrl: Network RPC endpoints.
* fee symbol: fee's symbol, It is a symbol that the wallet displays on the screen.
* fee decimals: fee's decimals.

#### Requirements

* `D'CENT Bridge` version 1.5.3 or higher is required.
* D'CENT Biometric Wallet version 2.30.1 or higher is required.

#### Useage 

```javascript
import { ApiPromise, HttpProvider } from '@polkadot/api'

const httpProvider = new HttpProvider('https://evm.astar.network');
const api = await ApiPromise({ provider: httpProvider });
// Wait until we are ready and connected
await api.isReady;

const blockNumber = await api.rpc.chain.getHeader();
const blockHash = await api.rpc.chain.getBlockHash(blockNumber.number.toHex());
// create SignerPayload
const signerPayload = api.createType('SignerPayload', {
  genesisHash: api.genesisHash,
  runtimeVersion: api.runtimeVersion,
  version: api.extrinsicVersion,
  blockHash: blockHash,
  blockNumber: blockNumber.number,
  era: api.createType('ExtrinsicEra', {
    current: blockNumber.number,
    period: 50
  }),
  nonce,
  address: to,
  method: api.tx.balances.transfer(to, amount).method, // For tokens, method: api.tx.assets.transfer(contract, to, amount).method,
});

const sigHash = signerPayload.toRaw().data;

const transactionJson = {
  coinType: DcentWebConnector.coinType.PARA,
  sigHash: sigHash,
  path: `m/44'/810'/0'/0/0`,
  decimals, // 18
  fee,
  symbol: 'ASTR',
  RPCUrl: 'https://evm.astar.network',
  feeSymbol: 'ASTR',
  feeDecimals, // 18
};

var result;
try {
  result = await DcentWebConnector.getParachainSignedTransaction(transactionJson);
} catch (e) {
  console.log(e);
  result = e;
}
```

#### Returned response object

```json
{
    "header": {
      "version": "1.0",
      "response_from": "para",
      "status": "success"
    },
    "body": {
      "command": "transaction",
      "parameter": {
        "signed_tx": "0x00263b3ed036c74d15d875c7246abe73404c82763f3300316eb782cafdf5bd93f4f47f0fe34d823f9d07f8db7b2cb81051e58a1e58993c70888916c0ef6c3c910f"
      }
    }
  }
```

Please note that for `Astar EVM` transactions, you can use the getEthereumSignedTransaction() and getTokenSignedTransaction() methods with the chain ID set to 592.


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