> ## Documentation Index
> Fetch the complete documentation index at: https://t2z.d4mr.com/llms.txt
> Use this file to discover all available pages before exploring further.

# get_sighash

> Get the signature hash for external signing

Computes the signature hash (sighash) for a transparent input, enabling external signing with hardware wallets or HSMs.

## Signature

<Tabs>
  <Tab title="TypeScript">
    ```typescript theme={null}
    function get_sighash(pczt: WasmPczt, input_index: number): string
    ```
  </Tab>

  <Tab title="Go">
    ```go theme={null}
    func GetSighash(pczt *Pczt, inputIndex uint32) ([]byte, error)
    ```
  </Tab>

  <Tab title="Kotlin">
    ```kotlin theme={null}
    fun getSighash(pczt: Pczt, inputIndex: UInt): ByteArray
    ```
  </Tab>
</Tabs>

## Parameters

<ResponseField name="pczt" type="Pczt" required>
  The PCZT containing the input to sign
</ResponseField>

<ResponseField name="input_index" type="number" required>
  Index of the transparent input (0-based)
</ResponseField>

## Returns

32-byte signature hash as hex string (TypeScript) or bytes (Go/Kotlin).

## Example

```typescript theme={null}
// Get sighash for input 0
const sighashHex = t2z.get_sighash(pczt, 0);
// "64a1ef0a32a709943685a39db55a5abf3bdd3e395f9b8ecd7dc618b2d2f88e9b"

// Sign with secp256k1 ECDSA
import { secp256k1 } from '@noble/curves/secp256k1';
const sig = secp256k1.sign(hexToBytes(sighashHex), privateKeyBytes);
const derSig = sig.toDERRawBytes();

// Append SIGHASH_ALL type
const sigWithType = new Uint8Array([...derSig, 0x01]);

// Add to PCZT
pczt = t2z.append_signature(pczt, 0, pubkeyHex, bytesToHex(sigWithType));
```

## Hardware Wallet Flow

```typescript theme={null}
// 1. Get sighash
const sighash = t2z.get_sighash(pczt, inputIndex);

// 2. Send to hardware wallet
const signature = await ledger.signMessage(
  hexToBytes(sighash),
  "m/44'/133'/0'/0/0"  // Zcash path
);

// 3. Append to PCZT
pczt = t2z.append_signature(pczt, inputIndex, pubkey, signature);
```

## See Also

* [`append_signature`](/api-reference/append-signature)
* [`sign_transparent_input`](/api-reference/sign-transparent-input)
* [Transaction Flow: Sign](/flow/sign)