> For the complete documentation index, see [llms.txt](https://docs-legacy.dfns.co/d/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-legacy.dfns.co/d/api-docs/keys/generate-signature/bitcoin.md).

# Bitcoin / Litecoin

Bitcoin and Litecoin chains support the following signature `kinds`:

* `Psbt`, partially signed bitcoin transaction, or PSBT.
* `Bip322`, generic message defined in [BIP-322](https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki).

## PSBT

Signs a partially signed bitcoin transaction.

| Field            | Description           | Type - Optional |
| ---------------- | --------------------- | --------------- |
| `blockchainKind` | `Bitcoin`             | String          |
| `kind`           | `Psbt`                | String          |
| `psbt`           | The hex encoded PSBT. | String          |

```json
{
  "blockchainKind": "Bitcoin",
  "kind": "Psbt",
  "psbt": "0x70736274ff0100710200000001ca17431a33a13d3ef8bfb041c8546071f9d3a609abe3c91efbed83265e1426730100000000ffffffff02e803000000000000160014a40a65b46ff36c53f1afb8e35e25a4c0bcfc9979d6d1150000000000160014237ad8ba2ffd992f6ebc7ab388e77f00fc87d1c9000000000001011f54d6150000000000160014237ad8ba2ffd992f6ebc7ab388e77f00fc87d1c9000000"
}
```

### Typescript Example with BitcoinJS <a href="#typescript-example" id="typescript-example"></a>

First install the BitcoinJS SDK. You can find the full documentation here: <https://github.com/bitcoinjs/bitcoinjs-lib>

Here a code sample to generate a signature via [the Dfns TypeScript SDK](https://github.com/dfns/dfns-sdk-ts):

```typescript
import { networks, payments, Psbt } from 'bitcoinjs-lib'
import axios from 'axios'

const walletId = 'wa-6lbfv-9esgj-xxxxxxxxxxxxxxxx'
const wallet = await dfnsClient.wallets.getWallet({ walletId })
const publicKey = Buffer.from(wallet.signingKey.publicKey, 'hex')

const network = networks.testnet
const { address } = payments.p2wpkh({
  pubkey: publicKey,
  network,
})

const txid = '87872516c6e93f136fc6c493c7172596b11c695e27889de7532abffcac2a4b5e'
const n = 1
const utxo = (
  await axios.post(BITCOIN_NODE_URL, {
    jsonrpc: '2.0',
    id: 'gettxout',
    method: 'gettxout',
    params: [txid, n, false],
  })
).data.result

const balance = utxo.balance * 100000000
const amount = 1
const fee = 150

const psbt = new Psbt({ network })
psbt.addInput({
  hash: txid,
  index: n,
  witnessUtxo: {
    script: Buffer.from(utxo.scriptPubKey.hex, 'hex'),
    value: balance,
  },
})

psbt.addOutput({
  address: 'tb1q5s9xtdr07dk98ud0hr34ufdycz70exte2kehm2',
  value: amount,
})

psbt.addOutput({
  address,
  value: balance - amount - fee,
})

const res = await dfnsClient.wallets.generateSignature({
  walletId,
  body: { kind: 'Psbt', psbt: `0x${psbt.toHex()}` },
})
```

## BIP-322

Signs a generic message using [BIP-322](https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki). Note: signing payload construction depends on the targeted blockchain. Therefore it's tied to a specific `network` rather than the blockchain kind.

| Field     | Description                                                                                                                                    | Type - Optional     |
| --------- | ---------------------------------------------------------------------------------------------------------------------------------------------- | ------------------- |
| `network` | A supported Bitcoin network.                                                                                                                   | String              |
| `kind`    | `Bip322`                                                                                                                                       | String              |
| `message` | The generic message hex encoded.                                                                                                               | String              |
| `format`  | Either `Simple` or `Full`. Defaults to `Simple` if not present. The formatted signature is returned in the `signedData` field in the response. | String *(optional)* |

```json
{
  "network": "Bitcoin",
  "kind": "Bip322",
  "message": "0x49206c6f76652044666e73"
}
```


---

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