computeReclaimSighash

Computes the BIP-143 SIGHASH_ALL digest for input 0 of a reclaim transaction, for signers that sign a bare digest. Pure computation: no network call.

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Usage

import { buildReclaim, computeReclaimSighash, finalizeReclaim } from '@stacks/bitcoin-staking';
import type { BuildReclaimOpts } from '@stacks/bitcoin-staking';

declare const opts: BuildReclaimOpts; // path: 'early-exit'
declare const stxAddress: string; // staker the lockup script commits to
declare const stakerPublicKey: Uint8Array;
declare const cosignerPublicKey: Uint8Array; // key in the bond's early-unlock subscript
// Each returns a DER signature with a trailing SIGHASH_ALL byte (0x01)
declare function stakerSign(digest: Uint8Array): Promise<Uint8Array>;
declare function cosignerSign(digest: Uint8Array): Promise<Uint8Array>;

const tx = buildReclaim(opts);
const sighash = computeReclaimSighash(tx);

tx.updateInput(0, {
  partialSig: [
    [stakerPublicKey, await stakerSign(sighash)],
    [cosignerPublicKey, await cosignerSign(sighash)],
  ],
});

const { txHex } = finalizeReclaim({ path: 'early-exit', tx, stxAddress });

Notes

• Typical digest signers are an HSM, a KMS or an MPC service. The staker and the cosigner can also exchange the early-exit digest out of band. With an in-process key, tx.signIdx(privateKey, 0) computes the digest itself. Hardware and browser wallets take the PSBT from tx.toPSBT() instead.
• Reads the witness script and input amount from the transaction, where buildReclaim sets them and a PSBT round trip keeps them. A transaction parsed from raw hex carries neither, so pass them in opts. Throws an Error if either is missing.
• The signature commits to the outputs. Recompute the digest after changing any output or the fee.

Reference Link

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Signature

function computeReclaimSighash(
  tx: btc.Transaction,
  opts?: { witnessScript?: Uint8Array | string; amountSats?: IntegerType }
): Uint8Array;

btc is @scure/btc-signer.

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Returns

Uint8Array

The 32-byte digest to sign.

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Parameters

tx (required)

• Type: btc.Transaction

The reclaim transaction, usually from buildReclaim.

opts.witnessScript (optional)

• Type: Uint8Array | string

The lockup witness script, as bytes or hex. Overrides the one on input 0.

opts.amountSats (optional)

• Type: IntegerType

The value of the lockup output being spent, in sats. Overrides the amount on input 0.