get_sighash

// 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));

// 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);