mod, utils, weierstrass, secp: improve hex errors. secp: improve verify() logic and schnorr

src/abstract/modular.ts

@@ -407,7 +407,7 @@ export function hashToPrivateScalar(
   groupOrder: bigint,
   isLE = false
 ): bigint {
-  hash = ensureBytes(hash);
+  hash = ensureBytes('privateHash', hash);
   const hashLen = hash.length;
   const minLen = nLength(groupOrder).nByteLength + 8;
   if (minLen < 24 || hashLen < minLen || hashLen > 1024)

src/abstract/utils.ts

@@ -33,14 +33,14 @@ export function numberToHexUnpadded(num: number | bigint): string {
 }
 
 export function hexToNumber(hex: string): bigint {
-  if (typeof hex !== 'string') throw new Error('string expected, got ' + typeof hex);
+  if (typeof hex !== 'string') throw new Error('hex string expected, got ' + typeof hex);
   // Big Endian
   return BigInt(hex === '' ? '0' : `0x${hex}`);
 }
 
 // Caching slows it down 2-3x
 export function hexToBytes(hex: string): Uint8Array {
-  if (typeof hex !== 'string') throw new Error('string expected, got ' + typeof hex);
+  if (typeof hex !== 'string') throw new Error('hex string expected, got ' + typeof hex);
   if (hex.length % 2) throw new Error('hex string is invalid: unpadded ' + hex.length);
   const array = new Uint8Array(hex.length / 2);
   for (let i = 0; i < array.length; i++) {
@@ -68,13 +68,25 @@ export const numberToBytesLE = (n: bigint, len: number) => numberToBytesBE(n, le
 // Returns variable number bytes (minimal bigint encoding?)
 export const numberToVarBytesBE = (n: bigint) => hexToBytes(numberToHexUnpadded(n));
 
-export function ensureBytes(hex: Hex, expectedLength?: number): Uint8Array {
+export function ensureBytes(title: string, hex: Hex, expectedLength?: number): Uint8Array {
+  let res: Uint8Array;
+  if (typeof hex === 'string') {
+    try {
+      res = hexToBytes(hex);
+    } catch (e) {
+      throw new Error(`${title} must be valid hex string, got "${hex}". Cause: ${e}`);
+    }
+  } else if (u8a(hex)) {
     // Uint8Array.from() instead of hash.slice() because node.js Buffer
     // is instance of Uint8Array, and its slice() creates **mutable** copy
-  const bytes = u8a(hex) ? Uint8Array.from(hex) : hexToBytes(hex);
+    res = Uint8Array.from(hex);
-  if (typeof expectedLength === 'number' && bytes.length !== expectedLength)
+  } else {
-    throw new Error(`Expected ${expectedLength} bytes`);
+    throw new Error(`${title} must be hex string or Uint8Array`);
-  return bytes;
+  }
+  const len = res.length;
+  if (typeof expectedLength === 'number' && len !== expectedLength)
+    throw new Error(`${title} expected ${expectedLength} bytes, got ${len}`);
+  return res;
 }
 
 // Copies several Uint8Arrays into one.
@@ -96,6 +108,16 @@ export function equalBytes(b1: Uint8Array, b2: Uint8Array) {
   return true;
 }
 
+// Global symbols in both browsers and Node.js since v11
+// See https://github.com/microsoft/TypeScript/issues/31535
+declare const TextEncoder: any;
+export function utf8ToBytes(str: string): Uint8Array {
+  if (typeof str !== 'string') {
+    throw new Error(`utf8ToBytes expected string, got ${typeof str}`);
+  }
+  return new TextEncoder().encode(str);
+}
+
 // Bit operations
 
 // Amount of bits inside bigint (Same as n.toString(2).length)

src/abstract/weierstrass.ts

@@ -59,9 +59,6 @@ export interface ProjPointType<T> extends Group<ProjPointType<T>> {
   readonly py: T;
   readonly pz: T;
   multiply(scalar: bigint): ProjPointType<T>;
-  multiplyUnsafe(scalar: bigint): ProjPointType<T>;
-  multiplyAndAddUnsafe(Q: ProjPointType<T>, a: bigint, b: bigint): ProjPointType<T> | undefined;
-  _setWindowSize(windowSize: number): void;
   toAffine(iz?: T): AffinePoint<T>;
   isTorsionFree(): boolean;
   clearCofactor(): ProjPointType<T>;
@@ -69,6 +66,10 @@ export interface ProjPointType<T> extends Group<ProjPointType<T>> {
   hasEvenY(): boolean;
   toRawBytes(isCompressed?: boolean): Uint8Array;
   toHex(isCompressed?: boolean): string;
+
+  multiplyUnsafe(scalar: bigint): ProjPointType<T>;
+  multiplyAndAddUnsafe(Q: ProjPointType<T>, a: bigint, b: bigint): ProjPointType<T> | undefined;
+  _setWindowSize(windowSize: number): void;
 }
 // Static methods for 3d XYZ points
 export interface ProjConstructor<T> extends GroupConstructor<ProjPointType<T>> {
@@ -213,7 +214,10 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
     }
     let num: bigint;
     try {
-      num = typeof key === 'bigint' ? key : ut.bytesToNumberBE(ensureBytes(key, nByteLength));
+      num =
+        typeof key === 'bigint'
+          ? key
+          : ut.bytesToNumberBE(ensureBytes('private key', key, nByteLength));
     } catch (error) {
       throw new Error(`private key must be ${nByteLength} bytes, hex or bigint, not ${typeof key}`);
     }
@@ -276,7 +280,7 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
      * @param hex short/long ECDSA hex
      */
     static fromHex(hex: Hex): Point {
-      const P = Point.fromAffine(CURVE.fromBytes(ensureBytes(hex)));
+      const P = Point.fromAffine(CURVE.fromBytes(ensureBytes('pointHex', hex)));
       P.assertValidity();
       return P;
     }
@@ -782,24 +786,22 @@ export function weierstrass(curveDef: CurveType): CurveFn {
 
     // pair (bytes of r, bytes of s)
     static fromCompact(hex: Hex) {
-      const gl = CURVE.nByteLength;
+      const l = CURVE.nByteLength;
-      hex = ensureBytes(hex, gl * 2);
+      hex = ensureBytes('compactSignature', hex, l * 2);
-      return new Signature(slcNum(hex, 0, gl), slcNum(hex, gl, 2 * gl));
+      return new Signature(slcNum(hex, 0, l), slcNum(hex, l, 2 * l));
     }
 
     // DER encoded ECDSA signature
     // https://bitcoin.stackexchange.com/questions/57644/what-are-the-parts-of-a-bitcoin-transaction-input-script
     static fromDER(hex: Hex) {
-      if (typeof hex !== 'string' && !(hex instanceof Uint8Array))
+      const { r, s } = DER.toSig(ensureBytes('DER', hex));
-        throw new Error(`Signature.fromDER: Expected string or Uint8Array`);
-      const { r, s } = DER.toSig(ensureBytes(hex));
       return new Signature(r, s);
     }
 
     assertValidity(): void {
       // can use assertGE here
-      if (!isWithinCurveOrder(this.r)) throw new Error('r must be 0 < r < n');
+      if (!isWithinCurveOrder(this.r)) throw new Error('r must be 0 < r < CURVE.n');
-      if (!isWithinCurveOrder(this.s)) throw new Error('s must be 0 < s < n');
+      if (!isWithinCurveOrder(this.s)) throw new Error('s must be 0 < s < CURVE.n');
     }
 
     addRecoveryBit(recovery: number) {
@@ -807,11 +809,10 @@ export function weierstrass(curveDef: CurveType): CurveFn {
     }
 
     recoverPublicKey(msgHash: Hex): typeof Point.BASE {
-      const { n: N } = CURVE; // ECDSA public key recovery secg.org/sec1-v2.pdf 4.1.6
       const { r, s, recovery: rec } = this;
-      const h = bits2int_modN(ensureBytes(msgHash)); // Truncate hash
+      const h = bits2int_modN(ensureBytes('msgHash', msgHash)); // Truncate hash
       if (rec == null || ![0, 1, 2, 3].includes(rec)) throw new Error('recovery id invalid');
-      const radj = rec === 2 || rec === 3 ? r + N : r;
+      const radj = rec === 2 || rec === 3 ? r + CURVE.n : r;
       if (radj >= Fp.ORDER) throw new Error('recovery id 2 or 3 invalid');
       const prefix = (rec & 1) === 0 ? '02' : '03';
       const R = Point.fromHex(prefix + numToNByteStr(radj));
@@ -936,8 +937,8 @@ export function weierstrass(curveDef: CurveType): CurveFn {
     function (bytes: Uint8Array): bigint {
       // For curves with nBitLength % 8 !== 0: bits2octets(bits2octets(m)) !== bits2octets(m)
       // for some cases, since bytes.length * 8 is not actual bitLength.
-      const delta = bytes.length * 8 - CURVE.nBitLength; // truncate to nBitLength leftmost bits
       const num = ut.bytesToNumberBE(bytes); // check for == u8 done here
+      const delta = bytes.length * 8 - CURVE.nBitLength; // truncate to nBitLength leftmost bits
       return delta > 0 ? num >> BigInt(delta) : num;
     };
   const bits2int_modN =
@@ -962,26 +963,25 @@ export function weierstrass(curveDef: CurveType): CurveFn {
   // NOTE: we cannot assume here that msgHash has same amount of bytes as curve order, this will be wrong at least for P521.
   // Also it can be bigger for P224 + SHA256
   function prepSig(msgHash: Hex, privateKey: PrivKey, opts = defaultSigOpts) {
-    const { hash, randomBytes } = CURVE;
-    if (msgHash == null) throw new Error(`sign: expected valid message hash, not "${msgHash}"`);
     if (['recovered', 'canonical'].some((k) => k in opts))
-      // Ban legacy options
       throw new Error('sign() legacy options not supported');
+    const { hash, randomBytes } = CURVE;
     let { lowS, prehash, extraEntropy: ent } = opts; // generates low-s sigs by default
-    if (prehash) msgHash = hash(ensureBytes(msgHash));
     if (lowS == null) lowS = true; // RFC6979 3.2: we skip step A, because we already provide hash
+    msgHash = ensureBytes('msgHash', msgHash);
+    if (prehash) msgHash = ensureBytes('prehashed msgHash', hash(msgHash));
 
     // We can't later call bits2octets, since nested bits2int is broken for curves
     // with nBitLength % 8 !== 0. Because of that, we unwrap it here as int2octets call.
     // const bits2octets = (bits) => int2octets(bits2int_modN(bits))
-    const h1int = bits2int_modN(ensureBytes(msgHash));
+    const h1int = bits2int_modN(msgHash);
     const d = normalizePrivateKey(privateKey); // validate private key, convert to bigint
     const seedArgs = [int2octets(d), int2octets(h1int)];
     // extraEntropy. RFC6979 3.6: additional k' (optional).
     if (ent != null) {
       // K = HMAC_K(V || 0x00 || int2octets(x) || bits2octets(h1) || k')
-      // Either pass as-is, or generate random bytes. Then validate for being ui8a of size BYTES
+      const e = ent === true ? randomBytes(Fp.BYTES) : ent; // generate random bytes OR pass as-is
-      seedArgs.push(ensureBytes(ent === true ? randomBytes(Fp.BYTES) : ent, Fp.BYTES));
+      seedArgs.push(ensureBytes('extraEntropy', e, Fp.BYTES)); // check for being of size BYTES
     }
     const seed = ut.concatBytes(...seedArgs); // Step D of RFC6979 3.2
     const m = h1int; // NOTE: no need to call bits2int second time here, it is inside truncateHash!
@@ -1057,30 +1057,38 @@ export function weierstrass(curveDef: CurveType): CurveFn {
     publicKey: Hex,
     opts = defaultVerOpts
   ): boolean {
-    let P: ProjPointType<bigint>;
+    const sg = signature;
+    msgHash = ensureBytes('msgHash', msgHash);
+    publicKey = ensureBytes('publicKey', publicKey);
+    if ('strict' in opts) throw new Error('options.strict was renamed to lowS');
+    const { lowS, prehash } = opts;
+
     let _sig: Signature | undefined = undefined;
-    if (publicKey instanceof Point) throw new Error('publicKey must be hex');
+    let P: ProjPointType<bigint>;
     try {
-      if (signature && typeof signature === 'object' && !(signature instanceof Uint8Array)) {
+      if (typeof sg === 'string' || sg instanceof Uint8Array) {
-        const { r, s } = signature;
-        _sig = new Signature(r, s); // assertValidity() is executed on creation
-      } else {
         // Signature can be represented in 2 ways: compact (2*nByteLength) & DER (variable-length).
         // Since DER can also be 2*nByteLength bytes, we check for it first.
         try {
-          _sig = Signature.fromDER(signature as Hex);
+          _sig = Signature.fromDER(sg);
         } catch (derError) {
           if (!(derError instanceof DER.Err)) throw derError;
-          _sig = Signature.fromCompact(signature as Hex);
+          _sig = Signature.fromCompact(sg);
         }
+      } else if (typeof sg === 'object' && typeof sg.r === 'bigint' && typeof sg.s === 'bigint') {
+        const { r, s } = sg;
+        _sig = new Signature(r, s);
+      } else {
+        throw new Error('PARSE');
       }
-      msgHash = ensureBytes(msgHash);
       P = Point.fromHex(publicKey);
     } catch (error) {
+      if ((error as Error).message === 'PARSE')
+        throw new Error(`signature must be Signature instance, Uint8Array or hex string`);
       return false;
     }
-    if (opts.lowS && _sig.hasHighS()) return false;
+    if (lowS && _sig.hasHighS()) return false;
-    if (opts.prehash) msgHash = CURVE.hash(msgHash);
+    if (prehash) msgHash = CURVE.hash(msgHash);
     const { r, s } = _sig;
     const h = bits2int_modN(msgHash); // Cannot use fields methods, since it is group element
     const is = invN(s); // s^-1

src/secp256k1.ts

@@ -1,26 +1,12 @@
 /*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
 import { sha256 } from '@noble/hashes/sha256';
-import { Fp as Field, mod, pow2 } from './abstract/modular.js';
-import { createCurve } from './_shortw_utils.js';
-import { ProjPointType as PointType, mapToCurveSimpleSWU } from './abstract/weierstrass.js';
-import {
-  ensureBytes,
-  concatBytes,
-  Hex,
-  bytesToNumberBE as bytesToInt,
-  PrivKey,
-  numberToBytesBE,
-} from './abstract/utils.js';
 import { randomBytes } from '@noble/hashes/utils';
+import { Fp as Field, mod, pow2 } from './abstract/modular.js';
+import { ProjPointType as PointType, mapToCurveSimpleSWU } from './abstract/weierstrass.js';
+import type { Hex, PrivKey } from './abstract/utils.js';
+import { bytesToNumberBE, concatBytes, ensureBytes, numberToBytesBE } from './abstract/utils.js';
 import * as htf from './abstract/hash-to-curve.js';
-
+import { createCurve } from './_shortw_utils.js';
-/**
- * secp256k1 belongs to Koblitz curves: it has efficiently computable endomorphism.
- * Endomorphism uses 2x less RAM, speeds up precomputation by 2x and ECDH / key recovery by 20%.
- * Should always be used for Projective's double-and-add multiplication.
- * For affines cached multiplication, it trades off 1/2 init time & 1/3 ram for 20% perf hit.
- * https://gist.github.com/paulmillr/eb670806793e84df628a7c434a873066
- */
 
 const secp256k1P = BigInt('0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f');
 const secp256k1N = BigInt('0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141');
@@ -61,23 +47,22 @@ type Fp = bigint;
 
 export const secp256k1 = createCurve(
   {
-    // Params: a, b
+    a: BigInt(0), // equation params: a, b
-    // Seem to be rigid https://bitcointalk.org/index.php?topic=289795.msg3183975#msg3183975
+    b: BigInt(7), // Seem to be rigid: bitcointalk.org/index.php?topic=289795.msg3183975#msg3183975
-    a: BigInt(0),
+    Fp, // Field's prime: 2n**256n - 2n**32n - 2n**9n - 2n**8n - 2n**7n - 2n**6n - 2n**4n - 1n
-    b: BigInt(7),
+    n: secp256k1N, // Curve order, total count of valid points in the field
-    // Field over which we'll do calculations;
-    // 2n**256n - 2n**32n - 2n**9n - 2n**8n - 2n**7n - 2n**6n - 2n**4n - 1n
-    Fp,
-    // Curve order, total count of valid points in the field
-    n: secp256k1N,
     // Base point (x, y) aka generator point
     Gx: BigInt('55066263022277343669578718895168534326250603453777594175500187360389116729240'),
     Gy: BigInt('32670510020758816978083085130507043184471273380659243275938904335757337482424'),
-    h: BigInt(1),
+    h: BigInt(1), // Cofactor
-    // Alllow only low-S signatures by default in sign() and verify()
+    lowS: true, // Allow only low-S signatures by default in sign() and verify()
-    lowS: true,
+    /**
+     * secp256k1 belongs to Koblitz curves: it has efficiently computable endomorphism.
+     * Endomorphism uses 2x less RAM, speeds up precomputation by 2x and ECDH / key recovery by 20%.
+     * For precomputed wNAF it trades off 1/2 init time & 1/3 ram for 20% perf hit.
+     * Explanation: https://gist.github.com/paulmillr/eb670806793e84df628a7c434a873066
+     */
     endo: {
-      // Params taken from https://gist.github.com/paulmillr/eb670806793e84df628a7c434a873066
       beta: BigInt('0x7ae96a2b657c07106e64479eac3434e99cf0497512f58995c1396c28719501ee'),
       splitScalar: (k: bigint) => {
         const n = secp256k1N;
@@ -105,19 +90,11 @@ export const secp256k1 = createCurve(
   sha256
 );
 
-// Schnorr signatures are superior to ECDSA from above.
+// Schnorr signatures are superior to ECDSA from above. Below is Schnorr-specific BIP0340 code.
-// Below is Schnorr-specific code as per BIP0340.
 // https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki
 const _0n = BigInt(0);
 const fe = (x: bigint) => typeof x === 'bigint' && _0n < x && x < secp256k1P;
 const ge = (x: bigint) => typeof x === 'bigint' && _0n < x && x < secp256k1N;
-
-const TAGS = {
-  challenge: 'BIP0340/challenge',
-  aux: 'BIP0340/aux',
-  nonce: 'BIP0340/nonce',
-} as const;
-
 /** An object mapping tags to their tagged hash prefix of [SHA256(tag) | SHA256(tag)] */
 const TAGGED_HASH_PREFIXES: { [tag: string]: Uint8Array } = {};
 function taggedHash(tag: string, ...messages: Uint8Array[]): Uint8Array {
@@ -132,49 +109,53 @@ function taggedHash(tag: string, ...messages: Uint8Array[]): Uint8Array {
 
 const pointToBytes = (point: PointType<bigint>) => point.toRawBytes(true).slice(1);
 const numTo32b = (n: bigint) => numberToBytesBE(n, 32);
+const modP = (x: bigint) => mod(x, secp256k1P);
 const modN = (x: bigint) => mod(x, secp256k1N);
 const Point = secp256k1.ProjectivePoint;
 const GmulAdd = (Q: PointType<bigint>, a: bigint, b: bigint) =>
   Point.BASE.multiplyAndAddUnsafe(Q, a, b);
-const hex32ToInt = (key: Hex) => bytesToInt(ensureBytes(key, 32));
 function schnorrGetExtPubKey(priv: PrivKey) {
-  let d = typeof priv === 'bigint' ? priv : hex32ToInt(priv);
+  const d = secp256k1.utils.normPrivateKeyToScalar(priv);
   const point = Point.fromPrivateKey(d); // P = d'⋅G; 0 < d' < n check is done inside
   const scalar = point.hasEvenY() ? d : modN(-d); // d = d' if has_even_y(P), otherwise d = n-d'
   return { point, scalar, bytes: pointToBytes(point) };
 }
 function lift_x(x: bigint): PointType<bigint> {
   if (!fe(x)) throw new Error('bad x: need 0 < x < p'); // Fail if x ≥ p.
-  const c = mod(x * x * x + BigInt(7), secp256k1P); // Let c = x³ + 7 mod p.
+  const xx = modP(x * x);
+  const c = modP(xx * x + BigInt(7)); // Let c = x³ + 7 mod p.
   let y = sqrtMod(c); // Let y = c^(p+1)/4 mod p.
-  if (y % 2n !== 0n) y = mod(-y, secp256k1P); // Return the unique point P such that x(P) = x and
+  if (y % 2n !== 0n) y = modP(-y); // Return the unique point P such that x(P) = x and
   const p = new Point(x, y, _1n); // y(P) = y if y mod 2 = 0 or y(P) = p-y otherwise.
   p.assertValidity();
   return p;
 }
 function challenge(...args: Uint8Array[]): bigint {
-  return modN(bytesToInt(taggedHash(TAGS.challenge, ...args)));
+  return modN(bytesToNumberBE(taggedHash('BIP0340/challenge', ...args)));
 }
 
-// Schnorr's pubkey is just `x` of Point (BIP340)
+/**
+ * Schnorr public key is just `x` coordinate of Point as per BIP340.
+ */
 function schnorrGetPublicKey(privateKey: Hex): Uint8Array {
   return schnorrGetExtPubKey(privateKey).bytes; // d'=int(sk). Fail if d'=0 or d'≥n. Ret bytes(d'⋅G)
 }
 
-// Creates Schnorr signature as per BIP340. Verifies itself before returning anything.
+/**
-// auxRand is optional and is not the sole source of k generation: bad CSPRNG won't be dangerous
+ * Creates Schnorr signature as per BIP340. Verifies itself before returning anything.
+ * auxRand is optional and is not the sole source of k generation: bad CSPRNG won't be dangerous.
+ */
 function schnorrSign(
   message: Hex,
   privateKey: PrivKey,
   auxRand: Hex = randomBytes(32)
 ): Uint8Array {
-  if (message == null) throw new Error(`sign: Expected valid message, not "${message}"`);
+  const m = ensureBytes('message', message);
-  const m = ensureBytes(message); // checks for isWithinCurveOrder
+  const { bytes: px, scalar: d } = schnorrGetExtPubKey(privateKey); // checks for isWithinCurveOrder
-  const { bytes: px, scalar: d } = schnorrGetExtPubKey(privateKey);
+  const a = ensureBytes('auxRand', auxRand, 32); // Auxiliary random data a: a 32-byte array
-  const a = ensureBytes(auxRand, 32); // Auxiliary random data a: a 32-byte array
+  const t = numTo32b(d ^ bytesToNumberBE(taggedHash('BIP0340/aux', a))); // Let t be the byte-wise xor of bytes(d) and hash/aux(a)
-  const t = numTo32b(d ^ bytesToInt(taggedHash(TAGS.aux, a))); // Let t be the byte-wise xor of bytes(d) and hash/aux(a)
+  const rand = taggedHash('BIP0340/nonce', t, px, m); // Let rand = hash/nonce(t || bytes(P) || m)
-  const rand = taggedHash(TAGS.nonce, t, px, m); // Let rand = hash/nonce(t || bytes(P) || m)
+  const k_ = modN(bytesToNumberBE(rand)); // Let k' = int(rand) mod n
-  const k_ = modN(bytesToInt(rand)); // Let k' = int(rand) mod n
   if (k_ === _0n) throw new Error('sign failed: k is zero'); // Fail if k' = 0.
   const { point: R, bytes: rx, scalar: k } = schnorrGetExtPubKey(k_); // Let R = k'⋅G.
   const e = challenge(rx, px, m); // Let e = int(hash/challenge(bytes(R) || bytes(P) || m)) mod n.
@@ -187,18 +168,19 @@ function schnorrSign(
 }
 
 /**
- * Verifies Schnorr signature synchronously.
+ * Verifies Schnorr signature.
  */
 function schnorrVerify(signature: Hex, message: Hex, publicKey: Hex): boolean {
+  const sig = ensureBytes('signature', signature, 64);
+  const m = ensureBytes('message', message);
+  const pub = ensureBytes('publicKey', publicKey, 32);
   try {
-    const P = lift_x(hex32ToInt(publicKey)); // P = lift_x(int(pk)); fail if that fails
+    const P = lift_x(bytesToNumberBE(pub)); // P = lift_x(int(pk)); fail if that fails
-    const sig = ensureBytes(signature, 64);
+    const r = bytesToNumberBE(sig.subarray(0, 32)); // Let r = int(sig[0:32]); fail if r ≥ p.
-    const r = bytesToInt(sig.subarray(0, 32)); // Let r = int(sig[0:32]); fail if r ≥ p.
     if (!fe(r)) return false;
-    const s = bytesToInt(sig.subarray(32, 64)); // Let s = int(sig[32:64]); fail if s ≥ n.
+    const s = bytesToNumberBE(sig.subarray(32, 64)); // Let s = int(sig[32:64]); fail if s ≥ n.
     if (!ge(s)) return false;
-    const m = ensureBytes(message);
+    const e = challenge(numTo32b(r), pointToBytes(P), m); // int(challenge(bytes(r)||bytes(P)||m))%n
-    const e = challenge(numTo32b(r), pointToBytes(P), m); // int(challenge(bytes(r)||bytes(P)||m)) mod n
     const R = GmulAdd(P, s, modN(-e)); // R = s⋅G - e⋅P
     if (!R || !R.hasEvenY() || R.toAffine().x !== r) return false; // -eP == (n-e)P
     return true; // Fail if is_infinite(R) / not has_even_y(R) / x(R) ≠ r.
@@ -212,11 +194,12 @@ export const schnorr = {
   sign: schnorrSign,
   verify: schnorrVerify,
   utils: {
+    randomPrivateKey: secp256k1.utils.randomPrivateKey,
     getExtendedPublicKey: schnorrGetExtPubKey,
     lift_x,
     pointToBytes,
     numberToBytesBE,
-    bytesToNumberBE: bytesToInt,
+    bytesToNumberBE,
     taggedHash,
     mod,
   },
@@ -259,7 +242,7 @@ const mapSWU = mapToCurveSimpleSWU(Fp, {
   B: BigInt('1771'),
   Z: Fp.create(BigInt('-11')),
 });
-const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+export const { hashToCurve, encodeToCurve } = htf.hashToCurve(
   secp256k1.ProjectivePoint,
   (scalars: bigint[]) => {
     const { x, y } = mapSWU(Fp.create(scalars[0]));
@@ -275,4 +258,3 @@ const { hashToCurve, encodeToCurve } = htf.hashToCurve(
     hash: sha256,
   }
 );
-export { hashToCurve, encodeToCurve };