Add taggedHash, sigHash v1

Co-authored-by: Brandon Black <brandonblack@bitgo.com>
Co-authored-by: Otto Allmendinger <otto@bitgo.com>
Co-authored-by: Tyler Levine <tyler@bitgo.com>
Co-authored-by: Daniel McNally <danielmcnally@bitgo.com>

package-lock.json

@@ -416,9 +416,9 @@
       "dev": true
     },
     "@types/node": {
-      "version": "16.11.1",
+      "version": "16.11.7",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-16.11.1.tgz",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-16.11.7.tgz",
-      "integrity": "sha512-PYGcJHL9mwl1Ek3PLiYgyEKtwTMmkMw4vbiyz/ps3pfdRYLVv+SN7qHVAImrjdAXxgluDEw6Ph4lyv+m9UpRmA==",
+      "integrity": "sha512-QB5D2sqfSjCmTuWcBWyJ+/44bcjO7VbjSbOE0ucoVbAsSNQc4Lt6QkgkVXkTDwkL4z/beecZNDvVX15D4P8Jbw==",
       "dev": true
     },
     "@types/proxyquire": {

package.json

@@ -62,7 +62,7 @@
     "@types/bs58check": "^2.1.0",
     "@types/create-hash": "^1.2.2",
     "@types/mocha": "^5.2.7",
-    "@types/node": "^16.11.1",
+    "@types/node": "^16.11.7",
     "@types/proxyquire": "^1.3.28",
     "@types/randombytes": "^2.0.0",
     "@types/wif": "^2.0.2",

src/bufferutils.d.ts

@@ -11,6 +11,7 @@ export declare function cloneBuffer(buffer: Buffer): Buffer;
 export declare class BufferWriter {
     buffer: Buffer;
     offset: number;
+    static withCapacity(size: number): BufferWriter;
     constructor(buffer: Buffer, offset?: number);
     writeUInt8(i: number): void;
     writeInt32(i: number): void;
@@ -20,6 +21,7 @@ export declare class BufferWriter {
     writeSlice(slice: Buffer): void;
     writeVarSlice(slice: Buffer): void;
     writeVector(vector: Buffer[]): void;
+    end(): Buffer;
 }
 /**
  * Helper class for reading of bitcoin data types from a buffer.

src/bufferutils.js

@@ -58,6 +58,9 @@ class BufferWriter {
     this.offset = offset;
     typeforce(types.tuple(types.Buffer, types.UInt32), [buffer, offset]);
   }
+  static withCapacity(size) {
+    return new BufferWriter(Buffer.alloc(size));
+  }
   writeUInt8(i) {
     this.offset = this.buffer.writeUInt8(i, this.offset);
   }
@@ -88,6 +91,12 @@ class BufferWriter {
     this.writeVarInt(vector.length);
     vector.forEach(buf => this.writeVarSlice(buf));
   }
+  end() {
+    if (this.buffer.length === this.offset) {
+      return this.buffer;
+    }
+    throw new Error(`buffer size ${this.buffer.length}, offset ${this.offset}`);
+  }
 }
 exports.BufferWriter = BufferWriter;
 /**

src/crypto.d.ts

@@ -4,3 +4,7 @@ export declare function sha1(buffer: Buffer): Buffer;
 export declare function sha256(buffer: Buffer): Buffer;
 export declare function hash160(buffer: Buffer): Buffer;
 export declare function hash256(buffer: Buffer): Buffer;
+declare const TAGS: readonly ["BIP0340/challenge", "BIP0340/aux", "BIP0340/nonce", "TapLeaf", "TapBranch", "TapSighash", "TapTweak", "KeyAgg list", "KeyAgg coefficient"];
+export declare type TaggedHashPrefix = typeof TAGS[number];
+export declare function taggedHash(prefix: TaggedHashPrefix, data: Buffer): Buffer;
+export {};

src/crypto.js

@@ -1,6 +1,6 @@
 'use strict';
 Object.defineProperty(exports, '__esModule', { value: true });
-exports.hash256 = exports.hash160 = exports.sha256 = exports.sha1 = exports.ripemd160 = void 0;
+exports.taggedHash = exports.hash256 = exports.hash160 = exports.sha256 = exports.sha1 = exports.ripemd160 = void 0;
 const createHash = require('create-hash');
 function ripemd160(buffer) {
   try {
@@ -34,3 +34,25 @@ function hash256(buffer) {
   return sha256(sha256(buffer));
 }
 exports.hash256 = hash256;
+const TAGS = [
+  'BIP0340/challenge',
+  'BIP0340/aux',
+  'BIP0340/nonce',
+  'TapLeaf',
+  'TapBranch',
+  'TapSighash',
+  'TapTweak',
+  'KeyAgg list',
+  'KeyAgg coefficient',
+];
+/** An object mapping tags to their tagged hash prefix of [SHA256(tag) | SHA256(tag)] */
+const TAGGED_HASH_PREFIXES = Object.fromEntries(
+  TAGS.map(tag => {
+    const tagHash = sha256(Buffer.from(tag));
+    return [tag, Buffer.concat([tagHash, tagHash])];
+  }),
+);
+function taggedHash(prefix, data) {
+  return sha256(Buffer.concat([TAGGED_HASH_PREFIXES[prefix], data]));
+}
+exports.taggedHash = taggedHash;

src/index.d.ts

@@ -5,6 +5,7 @@ import * as payments from './payments';
 import * as script from './script';
 export { address, crypto, networks, payments, script };
 export { Block } from './block';
+export { TaggedHashPrefix } from './crypto';
 export { Psbt, PsbtTxInput, PsbtTxOutput, Signer, SignerAsync, HDSigner, HDSignerAsync, } from './psbt';
 export { OPS as opcodes } from './ops';
 export { Transaction } from './transaction';

src/transaction.d.ts

@@ -12,10 +12,13 @@ export interface Input {
 }
 export declare class Transaction {
     static readonly DEFAULT_SEQUENCE = 4294967295;
+    static readonly SIGHASH_DEFAULT = 0;
     static readonly SIGHASH_ALL = 1;
     static readonly SIGHASH_NONE = 2;
     static readonly SIGHASH_SINGLE = 3;
     static readonly SIGHASH_ANYONECANPAY = 128;
+    static readonly SIGHASH_OUTPUT_MASK = 3;
+    static readonly SIGHASH_INPUT_MASK = 128;
     static readonly ADVANCED_TRANSACTION_MARKER = 0;
     static readonly ADVANCED_TRANSACTION_FLAG = 1;
     static fromBuffer(buffer: Buffer, _NO_STRICT?: boolean): Transaction;
@@ -42,6 +45,7 @@ export declare class Transaction {
      * This hash can then be used to sign the provided transaction input.
      */
     hashForSignature(inIndex: number, prevOutScript: Buffer, hashType: number): Buffer;
+    hashForWitnessV1(inIndex: number, prevOutScripts: Buffer[], values: number[], hashType: number, leafHash?: Buffer, annex?: Buffer): Buffer;
     hashForWitnessV0(inIndex: number, prevOutScript: Buffer, value: number, hashType: number): Buffer;
     getHash(forWitness?: boolean): Buffer;
     getId(): string;

src/transaction.js

@@ -20,7 +20,7 @@ function vectorSize(someVector) {
     }, 0)
   );
 }
-const EMPTY_SCRIPT = Buffer.allocUnsafe(0);
+const EMPTY_BUFFER = Buffer.allocUnsafe(0);
 const EMPTY_WITNESS = [];
 const ZERO = Buffer.from(
   '0000000000000000000000000000000000000000000000000000000000000000',
@@ -32,7 +32,7 @@ const ONE = Buffer.from(
 );
 const VALUE_UINT64_MAX = Buffer.from('ffffffffffffffff', 'hex');
 const BLANK_OUTPUT = {
-  script: EMPTY_SCRIPT,
+  script: EMPTY_BUFFER,
   valueBuffer: VALUE_UINT64_MAX,
 };
 function isOutput(out) {
@@ -124,7 +124,7 @@ class Transaction {
       this.ins.push({
         hash,
         index,
-        script: scriptSig || EMPTY_SCRIPT,
+        script: scriptSig || EMPTY_BUFFER,
         sequence: sequence,
         witness: EMPTY_WITNESS,
       }) - 1
@@ -247,7 +247,7 @@ class Transaction {
     } else {
       // "blank" others input scripts
       txTmp.ins.forEach(input => {
-        input.script = EMPTY_SCRIPT;
+        input.script = EMPTY_BUFFER;
       });
       txTmp.ins[inIndex].script = ourScript;
     }
@@ -257,6 +257,141 @@ class Transaction {
     txTmp.__toBuffer(buffer, 0, false);
     return bcrypto.hash256(buffer);
   }
+  hashForWitnessV1(inIndex, prevOutScripts, values, hashType, leafHash, annex) {
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#common-signature-message
+    typeforce(
+      types.tuple(
+        types.UInt32,
+        typeforce.arrayOf(types.Buffer),
+        typeforce.arrayOf(types.Satoshi),
+        types.UInt32,
+      ),
+      arguments,
+    );
+    if (
+      values.length !== this.ins.length ||
+      prevOutScripts.length !== this.ins.length
+    ) {
+      throw new Error('Must supply prevout script and value for all inputs');
+    }
+    const outputType =
+      hashType === Transaction.SIGHASH_DEFAULT
+        ? Transaction.SIGHASH_ALL
+        : hashType & Transaction.SIGHASH_OUTPUT_MASK;
+    const inputType = hashType & Transaction.SIGHASH_INPUT_MASK;
+    const isAnyoneCanPay = inputType === Transaction.SIGHASH_ANYONECANPAY;
+    const isNone = outputType === Transaction.SIGHASH_NONE;
+    const isSingle = outputType === Transaction.SIGHASH_SINGLE;
+    let hashPrevouts = EMPTY_BUFFER;
+    let hashAmounts = EMPTY_BUFFER;
+    let hashScriptPubKeys = EMPTY_BUFFER;
+    let hashSequences = EMPTY_BUFFER;
+    let hashOutputs = EMPTY_BUFFER;
+    if (!isAnyoneCanPay) {
+      let bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        36 * this.ins.length,
+      );
+      this.ins.forEach(txIn => {
+        bufferWriter.writeSlice(txIn.hash);
+        bufferWriter.writeUInt32(txIn.index);
+      });
+      hashPrevouts = bcrypto.sha256(bufferWriter.end());
+      bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        8 * this.ins.length,
+      );
+      values.forEach(value => bufferWriter.writeUInt64(value));
+      hashAmounts = bcrypto.sha256(bufferWriter.end());
+      bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        prevOutScripts.map(varSliceSize).reduce((a, b) => a + b),
+      );
+      prevOutScripts.forEach(prevOutScript =>
+        bufferWriter.writeVarSlice(prevOutScript),
+      );
+      hashScriptPubKeys = bcrypto.sha256(bufferWriter.end());
+      bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        4 * this.ins.length,
+      );
+      this.ins.forEach(txIn => bufferWriter.writeUInt32(txIn.sequence));
+      hashSequences = bcrypto.sha256(bufferWriter.end());
+    }
+    if (!(isNone || isSingle)) {
+      const txOutsSize = this.outs
+        .map(output => 8 + varSliceSize(output.script))
+        .reduce((a, b) => a + b);
+      const bufferWriter = bufferutils_1.BufferWriter.withCapacity(txOutsSize);
+      this.outs.forEach(out => {
+        bufferWriter.writeUInt64(out.value);
+        bufferWriter.writeVarSlice(out.script);
+      });
+      hashOutputs = bcrypto.sha256(bufferWriter.end());
+    } else if (isSingle && inIndex < this.outs.length) {
+      const output = this.outs[inIndex];
+      const bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        8 + varSliceSize(output.script),
+      );
+      bufferWriter.writeUInt64(output.value);
+      bufferWriter.writeVarSlice(output.script);
+      hashOutputs = bcrypto.sha256(bufferWriter.end());
+    }
+    const spendType = (leafHash ? 2 : 0) + (annex ? 1 : 0);
+    // Length calculation from:
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-14
+    // With extension from:
+    // https://github.com/bitcoin/bips/blob/master/bip-0342.mediawiki#signature-validation
+    const sigMsgSize =
+      174 -
+      (isAnyoneCanPay ? 49 : 0) -
+      (isNone ? 32 : 0) +
+      (annex ? 32 : 0) +
+      (leafHash ? 37 : 0);
+    const sigMsgWriter = bufferutils_1.BufferWriter.withCapacity(sigMsgSize);
+    sigMsgWriter.writeUInt8(hashType);
+    // Transaction
+    sigMsgWriter.writeInt32(this.version);
+    sigMsgWriter.writeUInt32(this.locktime);
+    sigMsgWriter.writeSlice(hashPrevouts);
+    sigMsgWriter.writeSlice(hashAmounts);
+    sigMsgWriter.writeSlice(hashScriptPubKeys);
+    sigMsgWriter.writeSlice(hashSequences);
+    if (!(isNone || isSingle)) {
+      sigMsgWriter.writeSlice(hashOutputs);
+    }
+    // Input
+    sigMsgWriter.writeUInt8(spendType);
+    if (isAnyoneCanPay) {
+      const input = this.ins[inIndex];
+      sigMsgWriter.writeSlice(input.hash);
+      sigMsgWriter.writeUInt32(input.index);
+      sigMsgWriter.writeUInt64(values[inIndex]);
+      sigMsgWriter.writeVarSlice(prevOutScripts[inIndex]);
+      sigMsgWriter.writeUInt32(input.sequence);
+    } else {
+      sigMsgWriter.writeUInt32(inIndex);
+    }
+    if (annex) {
+      const bufferWriter = bufferutils_1.BufferWriter.withCapacity(
+        varSliceSize(annex),
+      );
+      bufferWriter.writeVarSlice(annex);
+      sigMsgWriter.writeSlice(bcrypto.sha256(bufferWriter.end()));
+    }
+    // Output
+    if (isSingle) {
+      sigMsgWriter.writeSlice(hashOutputs);
+    }
+    // BIP342 extension
+    if (leafHash) {
+      sigMsgWriter.writeSlice(leafHash);
+      sigMsgWriter.writeUInt8(0);
+      sigMsgWriter.writeUInt32(0xffffffff);
+    }
+    // Extra zero byte because:
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-19
+    return bcrypto.taggedHash(
+      'TapSighash',
+      Buffer.concat([Buffer.of(0x00), sigMsgWriter.end()]),
+    );
+  }
   hashForWitnessV0(inIndex, prevOutScript, value, hashType) {
     typeforce(
       types.tuple(types.UInt32, types.Buffer, types.Satoshi, types.UInt32),
@@ -396,9 +531,12 @@ class Transaction {
 }
 exports.Transaction = Transaction;
 Transaction.DEFAULT_SEQUENCE = 0xffffffff;
+Transaction.SIGHASH_DEFAULT = 0x00;
 Transaction.SIGHASH_ALL = 0x01;
 Transaction.SIGHASH_NONE = 0x02;
 Transaction.SIGHASH_SINGLE = 0x03;
 Transaction.SIGHASH_ANYONECANPAY = 0x80;
+Transaction.SIGHASH_OUTPUT_MASK = 0x03;
+Transaction.SIGHASH_INPUT_MASK = 0x80;
 Transaction.ADVANCED_TRANSACTION_MARKER = 0x00;
 Transaction.ADVANCED_TRANSACTION_FLAG = 0x01;

test/bufferutils.spec.ts

@@ -66,6 +66,13 @@ describe('bufferutils', () => {
       );
     }
 
+    it('withCapacity', () => {
+      const expectedBuffer = Buffer.from('04030201', 'hex');
+      const withCapacity = BufferWriter.withCapacity(4);
+      withCapacity.writeInt32(0x01020304);
+      testBuffer(withCapacity, expectedBuffer);
+    });
+
     it('writeUint8', () => {
       const values = [0, 1, 254, 255];
       const expectedBuffer = Buffer.from([0, 1, 0xfe, 0xff]);
@@ -277,6 +284,16 @@ describe('bufferutils', () => {
       });
       testBuffer(bufferWriter, expectedBuffer);
     });
+
+    it('end', () => {
+      const expected = Buffer.from('0403020108070605', 'hex');
+      const bufferWriter = BufferWriter.withCapacity(8);
+      bufferWriter.writeUInt32(0x01020304);
+      bufferWriter.writeUInt32(0x05060708);
+      const result = bufferWriter.end();
+      testBuffer(bufferWriter, result);
+      testBuffer(bufferWriter, expected);
+    });
   });
 
   describe('BufferReader', () => {

test/crypto.spec.ts

@@ -1,12 +1,12 @@
 import * as assert from 'assert';
 import { describe, it } from 'mocha';
-import { crypto as bcrypto } from '..';
+import { crypto as bcrypto, TaggedHashPrefix } from '..';
 import * as fixtures from './fixtures/crypto.json';
 
 describe('crypto', () => {
   ['hash160', 'hash256', 'ripemd160', 'sha1', 'sha256'].forEach(algorithm => {
     describe(algorithm, () => {
-      fixtures.forEach(f => {
+      fixtures.hashes.forEach(f => {
         const fn = (bcrypto as any)[algorithm];
         const expected = (f as any)[algorithm];
 
@@ -19,4 +19,15 @@ describe('crypto', () => {
       });
     });
   });
+
+  describe('taggedHash', () => {
+    fixtures.taggedHash.forEach(f => {
+      const bytes = Buffer.from(f.hex, 'hex');
+      const expected = Buffer.from(f.result, 'hex');
+      it(`returns ${f.result} for taggedHash "${f.tag}" of ${f.hex}`, () => {
+        const actual = bcrypto.taggedHash(f.tag as TaggedHashPrefix, bytes);
+        assert.strictEqual(actual.toString('hex'), expected.toString('hex'));
+      });
+    });
+  });
 });

test/fixtures/crypto.json

@@ -1,4 +1,5 @@
-[
+{
+  "hashes": [
     {
       "hex": "0000000000000001",
       "hash160": "cdb00698f02afd929ffabea308340fa99ac2afa8",
@@ -31,4 +32,12 @@
       "sha1": "10d96fb43aca84e342206887bbeed3065d4e4344",
       "sha256": "a7fb8276035057ed6479c5f2305a96da100ac43f0ac10f277e5ab8c5457429da"
     }
+  ],
+  "taggedHash": [
+    {
+      "tag": "TapTweak",
+      "hex": "0101010101010101",
+      "result": "71ae15bad52efcecf4c9f672bfbded68a4adb8258f1b95f0d06aefdb5ebd14e9"
+    }
   ]
+}

test/fixtures/transaction.json

@@ -808,6 +808,87 @@
       "value": 987654321
     }
   ],
+  "taprootSigning": [
+    {
+      "description": "P2TR key path",
+      "utxos": [
+        {
+          "scriptHex": "512053a1f6e454df1aa2776a2814a721372d6258050de330b3c6d10ee8f4e0dda343",
+          "value": 420000000
+        },
+        {
+          "scriptHex": "5120147c9c57132f6e7ecddba9800bb0c4449251c92a1e60371ee77557b6620f3ea3",
+          "value": 462000000
+        },
+        {
+          "scriptHex": "76a914751e76e8199196d454941c45d1b3a323f1433bd688ac",
+          "value": 294000000
+        },
+        {
+          "scriptHex": "5120e4d810fd50586274face62b8a807eb9719cef49c04177cc6b76a9a4251d5450e",
+          "value": 504000000
+        },
+        {
+          "scriptHex": "512091b64d5324723a985170e4dc5a0f84c041804f2cd12660fa5dec09fc21783605",
+          "value": 630000000
+        },
+        {
+          "scriptHex": "00147dd65592d0ab2fe0d0257d571abf032cd9db93dc",
+          "value": 378000000
+        },
+        {
+          "scriptHex": "512075169f4001aa68f15bbed28b218df1d0a62cbbcf1188c6665110c293c907b831",
+          "value": 672000000
+        },
+        {
+          "scriptHex": "51200f63ca2c7639b9bb4be0465cc0aa3ee78a0761ba5f5f7d6ff8eab340f09da561",
+          "value": 546000000
+        },
+        {
+          "scriptHex": "5120053690babeabbb7850c32eead0acf8df990ced79f7a31e358fabf2658b4bc587",
+          "value": 588000000
+        }
+      ],
+      "txHex": "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",
+      "cases": [
+        {
+          "vin": 0,
+          "typeHex": "03",
+          "hash": "7e584883b084ace0469c6962a9a7d2a9060e1f3c218ab40d32c77651482122bc"
+        },
+        {
+          "vin": 1,
+          "typeHex": "83",
+          "hash": "325a644af47e8a5a2591cda0ab0723978537318f10e6a63d4eed783b96a71a4d"
+        },
+        {
+          "vin": 3,
+          "typeHex": "01",
+          "hash": "6ffd256e108685b41831385f57eebf2fca041bc6b5e607ea11b3e03d4cf9d9ba"
+        },
+        {
+          "vin": 4,
+          "typeHex": "00",
+          "hash": "9f90136737540ccc18707e1fd398ad222a1a7e4dd65cbfd22dbe4660191efa58"
+        },
+        {
+          "vin": 6,
+          "typeHex": "02",
+          "hash": "835c9ab6084ed9a8ae9b7cda21e0aa797aca3b76a54bd1e3c7db093f6c57e23f"
+        },
+        {
+          "vin": 7,
+          "typeHex": "82",
+          "hash": "df1cca638283c667084b8ffe6bf6e116cc5a53cf7ae1202c5fee45a9085f1ba5"
+        },
+        {
+          "vin": 8,
+          "typeHex": "81",
+          "hash": "30319859ca79ea1b7a9782e9daebc46e4ca4ca2bc04c9c53b2ec87fa83a526bd"
+        }
+      ]
+    }
+  ],
   "invalid": {
     "addInput": [
       {

test/transaction.spec.ts

@@ -328,6 +328,27 @@ describe('Transaction', () => {
     });
   });
 
+  describe('taprootSigning', () => {
+    fixtures.taprootSigning.forEach(f => {
+      const tx = Transaction.fromHex(f.txHex);
+      const prevOutScripts = f.utxos.map(({ scriptHex }) =>
+        Buffer.from(scriptHex, 'hex'),
+      );
+      const values = f.utxos.map(({ value }) => value);
+
+      f.cases.forEach(c => {
+        let hash: Buffer;
+
+        it(`should hash to ${c.hash} for ${f.description}:${c.vin}`, () => {
+          const hashType = Buffer.from(c.typeHex, 'hex').readUInt8(0);
+
+          hash = tx.hashForWitnessV1(c.vin, prevOutScripts, values, hashType);
+          assert.strictEqual(hash.toString('hex'), c.hash);
+        });
+      });
+    });
+  });
+
   describe('setWitness', () => {
     it('only accepts a a witness stack (Array of Buffers)', () => {
       assert.throws(() => {

ts_src/bufferutils.ts

@@ -58,6 +58,10 @@ export function cloneBuffer(buffer: Buffer): Buffer {
  * Helper class for serialization of bitcoin data types into a pre-allocated buffer.
  */
 export class BufferWriter {
+  static withCapacity(size: number): BufferWriter {
+    return new BufferWriter(Buffer.alloc(size));
+  }
+
   constructor(public buffer: Buffer, public offset: number = 0) {
     typeforce(types.tuple(types.Buffer, types.UInt32), [buffer, offset]);
   }
@@ -99,6 +103,13 @@ export class BufferWriter {
     this.writeVarInt(vector.length);
     vector.forEach((buf: Buffer) => this.writeVarSlice(buf));
   }
+
+  end(): Buffer {
+    if (this.buffer.length === this.offset) {
+      return this.buffer;
+    }
+    throw new Error(`buffer size ${this.buffer.length}, offset ${this.offset}`);
+  }
 }
 
 /**

ts_src/crypto.ts

@@ -31,3 +31,27 @@ export function hash160(buffer: Buffer): Buffer {
 export function hash256(buffer: Buffer): Buffer {
   return sha256(sha256(buffer));
 }
+
+const TAGS = [
+  'BIP0340/challenge',
+  'BIP0340/aux',
+  'BIP0340/nonce',
+  'TapLeaf',
+  'TapBranch',
+  'TapSighash',
+  'TapTweak',
+  'KeyAgg list',
+  'KeyAgg coefficient',
+] as const;
+export type TaggedHashPrefix = typeof TAGS[number];
+/** An object mapping tags to their tagged hash prefix of [SHA256(tag) | SHA256(tag)] */
+const TAGGED_HASH_PREFIXES = Object.fromEntries(
+  TAGS.map(tag => {
+    const tagHash = sha256(Buffer.from(tag));
+    return [tag, Buffer.concat([tagHash, tagHash])];
+  }),
+) as { [k in TaggedHashPrefix]: Buffer };
+
+export function taggedHash(prefix: TaggedHashPrefix, data: Buffer): Buffer {
+  return sha256(Buffer.concat([TAGGED_HASH_PREFIXES[prefix], data]));
+}

ts_src/index.ts

@@ -7,6 +7,7 @@ import * as script from './script';
 export { address, crypto, networks, payments, script };
 
 export { Block } from './block';
+export { TaggedHashPrefix } from './crypto';
 export {
   Psbt,
   PsbtTxInput,

ts_src/transaction.ts

@@ -27,7 +27,7 @@ function vectorSize(someVector: Buffer[]): number {
   );
 }
 
-const EMPTY_SCRIPT: Buffer = Buffer.allocUnsafe(0);
+const EMPTY_BUFFER: Buffer = Buffer.allocUnsafe(0);
 const EMPTY_WITNESS: Buffer[] = [];
 const ZERO: Buffer = Buffer.from(
   '0000000000000000000000000000000000000000000000000000000000000000',
@@ -39,7 +39,7 @@ const ONE: Buffer = Buffer.from(
 );
 const VALUE_UINT64_MAX: Buffer = Buffer.from('ffffffffffffffff', 'hex');
 const BLANK_OUTPUT = {
-  script: EMPTY_SCRIPT,
+  script: EMPTY_BUFFER,
   valueBuffer: VALUE_UINT64_MAX,
 };
 
@@ -62,10 +62,13 @@ export interface Input {
 
 export class Transaction {
   static readonly DEFAULT_SEQUENCE = 0xffffffff;
+  static readonly SIGHASH_DEFAULT = 0x00;
   static readonly SIGHASH_ALL = 0x01;
   static readonly SIGHASH_NONE = 0x02;
   static readonly SIGHASH_SINGLE = 0x03;
   static readonly SIGHASH_ANYONECANPAY = 0x80;
+  static readonly SIGHASH_OUTPUT_MASK = 0x03;
+  static readonly SIGHASH_INPUT_MASK = 0x80;
   static readonly ADVANCED_TRANSACTION_MARKER = 0x00;
   static readonly ADVANCED_TRANSACTION_FLAG = 0x01;
 
@@ -174,7 +177,7 @@ export class Transaction {
       this.ins.push({
         hash,
         index,
-        script: scriptSig || EMPTY_SCRIPT,
+        script: scriptSig || EMPTY_BUFFER,
         sequence: sequence as number,
         witness: EMPTY_WITNESS,
       }) - 1
@@ -326,7 +329,7 @@ export class Transaction {
     } else {
       // "blank" others input scripts
       txTmp.ins.forEach(input => {
-        input.script = EMPTY_SCRIPT;
+        input.script = EMPTY_BUFFER;
       });
       txTmp.ins[inIndex].script = ourScript;
     }
@@ -339,6 +342,158 @@ export class Transaction {
     return bcrypto.hash256(buffer);
   }
 
+  hashForWitnessV1(
+    inIndex: number,
+    prevOutScripts: Buffer[],
+    values: number[],
+    hashType: number,
+    leafHash?: Buffer,
+    annex?: Buffer,
+  ): Buffer {
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#common-signature-message
+    typeforce(
+      types.tuple(
+        types.UInt32,
+        typeforce.arrayOf(types.Buffer),
+        typeforce.arrayOf(types.Satoshi),
+        types.UInt32,
+      ),
+      arguments,
+    );
+
+    if (
+      values.length !== this.ins.length ||
+      prevOutScripts.length !== this.ins.length
+    ) {
+      throw new Error('Must supply prevout script and value for all inputs');
+    }
+
+    const outputType =
+      hashType === Transaction.SIGHASH_DEFAULT
+        ? Transaction.SIGHASH_ALL
+        : hashType & Transaction.SIGHASH_OUTPUT_MASK;
+
+    const inputType = hashType & Transaction.SIGHASH_INPUT_MASK;
+
+    const isAnyoneCanPay = inputType === Transaction.SIGHASH_ANYONECANPAY;
+    const isNone = outputType === Transaction.SIGHASH_NONE;
+    const isSingle = outputType === Transaction.SIGHASH_SINGLE;
+
+    let hashPrevouts = EMPTY_BUFFER;
+    let hashAmounts = EMPTY_BUFFER;
+    let hashScriptPubKeys = EMPTY_BUFFER;
+    let hashSequences = EMPTY_BUFFER;
+    let hashOutputs = EMPTY_BUFFER;
+
+    if (!isAnyoneCanPay) {
+      let bufferWriter = BufferWriter.withCapacity(36 * this.ins.length);
+      this.ins.forEach(txIn => {
+        bufferWriter.writeSlice(txIn.hash);
+        bufferWriter.writeUInt32(txIn.index);
+      });
+      hashPrevouts = bcrypto.sha256(bufferWriter.end());
+
+      bufferWriter = BufferWriter.withCapacity(8 * this.ins.length);
+      values.forEach(value => bufferWriter.writeUInt64(value));
+      hashAmounts = bcrypto.sha256(bufferWriter.end());
+
+      bufferWriter = BufferWriter.withCapacity(
+        prevOutScripts.map(varSliceSize).reduce((a, b) => a + b),
+      );
+      prevOutScripts.forEach(prevOutScript =>
+        bufferWriter.writeVarSlice(prevOutScript),
+      );
+      hashScriptPubKeys = bcrypto.sha256(bufferWriter.end());
+
+      bufferWriter = BufferWriter.withCapacity(4 * this.ins.length);
+      this.ins.forEach(txIn => bufferWriter.writeUInt32(txIn.sequence));
+      hashSequences = bcrypto.sha256(bufferWriter.end());
+    }
+
+    if (!(isNone || isSingle)) {
+      const txOutsSize = this.outs
+        .map(output => 8 + varSliceSize(output.script))
+        .reduce((a, b) => a + b);
+      const bufferWriter = BufferWriter.withCapacity(txOutsSize);
+
+      this.outs.forEach(out => {
+        bufferWriter.writeUInt64(out.value);
+        bufferWriter.writeVarSlice(out.script);
+      });
+
+      hashOutputs = bcrypto.sha256(bufferWriter.end());
+    } else if (isSingle && inIndex < this.outs.length) {
+      const output = this.outs[inIndex];
+
+      const bufferWriter = BufferWriter.withCapacity(
+        8 + varSliceSize(output.script),
+      );
+      bufferWriter.writeUInt64(output.value);
+      bufferWriter.writeVarSlice(output.script);
+      hashOutputs = bcrypto.sha256(bufferWriter.end());
+    }
+
+    const spendType = (leafHash ? 2 : 0) + (annex ? 1 : 0);
+
+    // Length calculation from:
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-14
+    // With extension from:
+    // https://github.com/bitcoin/bips/blob/master/bip-0342.mediawiki#signature-validation
+    const sigMsgSize =
+      174 -
+      (isAnyoneCanPay ? 49 : 0) -
+      (isNone ? 32 : 0) +
+      (annex ? 32 : 0) +
+      (leafHash ? 37 : 0);
+    const sigMsgWriter = BufferWriter.withCapacity(sigMsgSize);
+
+    sigMsgWriter.writeUInt8(hashType);
+    // Transaction
+    sigMsgWriter.writeInt32(this.version);
+    sigMsgWriter.writeUInt32(this.locktime);
+    sigMsgWriter.writeSlice(hashPrevouts);
+    sigMsgWriter.writeSlice(hashAmounts);
+    sigMsgWriter.writeSlice(hashScriptPubKeys);
+    sigMsgWriter.writeSlice(hashSequences);
+    if (!(isNone || isSingle)) {
+      sigMsgWriter.writeSlice(hashOutputs);
+    }
+    // Input
+    sigMsgWriter.writeUInt8(spendType);
+    if (isAnyoneCanPay) {
+      const input = this.ins[inIndex];
+      sigMsgWriter.writeSlice(input.hash);
+      sigMsgWriter.writeUInt32(input.index);
+      sigMsgWriter.writeUInt64(values[inIndex]);
+      sigMsgWriter.writeVarSlice(prevOutScripts[inIndex]);
+      sigMsgWriter.writeUInt32(input.sequence);
+    } else {
+      sigMsgWriter.writeUInt32(inIndex);
+    }
+    if (annex) {
+      const bufferWriter = BufferWriter.withCapacity(varSliceSize(annex));
+      bufferWriter.writeVarSlice(annex);
+      sigMsgWriter.writeSlice(bcrypto.sha256(bufferWriter.end()));
+    }
+    // Output
+    if (isSingle) {
+      sigMsgWriter.writeSlice(hashOutputs);
+    }
+    // BIP342 extension
+    if (leafHash) {
+      sigMsgWriter.writeSlice(leafHash);
+      sigMsgWriter.writeUInt8(0);
+      sigMsgWriter.writeUInt32(0xffffffff);
+    }
+
+    // Extra zero byte because:
+    // https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-19
+    return bcrypto.taggedHash(
+      'TapSighash',
+      Buffer.concat([Buffer.of(0x00), sigMsgWriter.end()]),
+    );
+  }
+
   hashForWitnessV0(
     inIndex: number,
     prevOutScript: Buffer,