hash-to-curve: decrease coupling, improve tree shaking support

src/abstract/bls.ts

@@ -15,12 +15,7 @@ import * as mod from './modular.js';
 import * as ut from './utils.js';
 // Types require separate import
 import { Hex, PrivKey } from './utils.js';
-import {
+import * as htf from './hash-to-curve.js';
-  htfOpts,
-  stringToBytes,
-  hash_to_field as hashToField,
-  expand_message_xmd as expandMessageXMD,
-} from './hash-to-curve.js';
 import { CurvePointsType, PointType, CurvePointsRes, weierstrassPoints } from './weierstrass.js';
 
 type Fp = bigint; // Can be different field?
@@ -32,9 +27,14 @@ export type SignatureCoder<Fp2> = {
 
 export type CurveType<Fp, Fp2, Fp6, Fp12> = {
   r: bigint;
-  G1: Omit<CurvePointsType<Fp>, 'n'>;
+  G1: Omit<CurvePointsType<Fp>, 'n'> & {
+    mapToCurve: htf.MapToCurve<Fp>;
+    htfDefaults: htf.Opts;
+  };
   G2: Omit<CurvePointsType<Fp2>, 'n'> & {
     Signature: SignatureCoder<Fp2>;
+    mapToCurve: htf.MapToCurve<Fp2>;
+    htfDefaults: htf.Opts;
   };
   x: bigint;
   Fp: mod.Field<Fp>;
@@ -51,7 +51,7 @@ export type CurveType<Fp, Fp2, Fp6, Fp12> = {
     conjugate(num: Fp12): Fp12;
     finalExponentiate(num: Fp12): Fp12;
   };
-  htfDefaults: htfOpts;
+  htfDefaults: htf.Opts;
   hash: ut.CHash; // Because we need outputLen for DRBG
   randomBytes: (bytesLength?: number) => Uint8Array;
 };
@@ -68,6 +68,11 @@ export type CurveFn<Fp, Fp2, Fp6, Fp12> = {
   Signature: SignatureCoder<Fp2>;
   millerLoop: (ell: [Fp2, Fp2, Fp2][], g1: [Fp, Fp]) => Fp12;
   calcPairingPrecomputes: (x: Fp2, y: Fp2) => [Fp2, Fp2, Fp2][];
+  // prettier-ignore
+  hashToCurve: {
+    G1: ReturnType<(typeof htf.hashToCurve<Fp>)>,
+    G2: ReturnType<(typeof htf.hashToCurve<Fp2>)>,
+  },
   pairing: (P: PointType<Fp>, Q: PointType<Fp2>, withFinalExponent?: boolean) => Fp12;
   getPublicKey: (privateKey: PrivKey) => Uint8Array;
   sign: {
@@ -93,11 +98,9 @@ export type CurveFn<Fp, Fp2, Fp6, Fp12> = {
     publicKeys: (Hex | PointType<Fp>)[]
   ) => boolean;
   utils: {
-    stringToBytes: typeof stringToBytes;
+    stringToBytes: typeof htf.stringToBytes;
-    hashToField: typeof hashToField;
+    hashToField: typeof htf.hash_to_field;
-    expandMessageXMD: typeof expandMessageXMD;
+    expandMessageXMD: typeof htf.expand_message_xmd;
-    getDSTLabel: () => string;
-    setDSTLabel(newLabel: string): void;
   };
 };
 
@@ -174,26 +177,18 @@ export function bls<Fp2, Fp6, Fp12>(
   const utils = {
     hexToBytes: ut.hexToBytes,
     bytesToHex: ut.bytesToHex,
-    stringToBytes: stringToBytes,
+    stringToBytes: htf.stringToBytes,
     // TODO: do we need to export it here?
     hashToField: (
       msg: Uint8Array,
       count: number,
       options: Partial<typeof CURVE.htfDefaults> = {}
-    ) => hashToField(msg, count, { ...CURVE.htfDefaults, ...options }),
+    ) => htf.hash_to_field(msg, count, { ...CURVE.htfDefaults, ...options }),
     expandMessageXMD: (msg: Uint8Array, DST: Uint8Array, lenInBytes: number, H = CURVE.hash) =>
-      expandMessageXMD(msg, DST, lenInBytes, H),
+      htf.expand_message_xmd(msg, DST, lenInBytes, H),
     hashToPrivateKey: (hash: Hex): Uint8Array => Fr.toBytes(ut.hashToPrivateScalar(hash, CURVE.r)),
     randomBytes: (bytesLength: number = groupLen): Uint8Array => CURVE.randomBytes(bytesLength),
     randomPrivateKey: (): Uint8Array => utils.hashToPrivateKey(utils.randomBytes(groupLen + 8)),
-    getDSTLabel: () => CURVE.htfDefaults.DST,
-    setDSTLabel(newLabel: string) {
-      // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-3.1
-      if (typeof newLabel !== 'string' || newLabel.length > 2048 || newLabel.length === 0) {
-        throw new TypeError('Invalid DST');
-      }
-      CURVE.htfDefaults.DST = newLabel;
-    },
   };
 
   // Point on G1 curve: (x, y)
@@ -201,6 +196,10 @@ export function bls<Fp2, Fp6, Fp12>(
     n: Fr.ORDER,
     ...CURVE.G1,
   });
+  const G1HashToCurve = htf.hashToCurve(G1.Point, CURVE.G1.mapToCurve, {
+    ...CURVE.htfDefaults,
+    ...CURVE.G1.htfDefaults,
+  });
 
   // Sparse multiplication against precomputed coefficients
   // TODO: replace with weakmap?
@@ -227,6 +226,11 @@ export function bls<Fp2, Fp6, Fp12>(
     n: Fr.ORDER,
     ...CURVE.G2,
   });
+  const G2HashToCurve = htf.hashToCurve(G2.Point, CURVE.G2.mapToCurve, {
+    ...CURVE.htfDefaults,
+    ...CURVE.G2.htfDefaults,
+  });
+
   const { Signature } = CURVE.G2;
 
   // Calculates bilinear pairing
@@ -250,8 +254,8 @@ export function bls<Fp2, Fp6, Fp12>(
   function normP2(point: G2Hex): G2 {
     return point instanceof G2.Point ? point : Signature.decode(point);
   }
-  function normP2Hash(point: G2Hex): G2 {
+  function normP2Hash(point: G2Hex, htfOpts?: htf.htfBasicOpts): G2 {
-    return point instanceof G2.Point ? point : G2.Point.hashToCurve(point);
+    return point instanceof G2.Point ? point : (G2HashToCurve.hashToCurve(point, htfOpts) as G2);
   }
 
   // Multiplies generator by private key.
@@ -262,10 +266,10 @@ export function bls<Fp2, Fp6, Fp12>(
 
   // Executes `hashToCurve` on the message and then multiplies the result by private key.
   // S = pk x H(m)
-  function sign(message: Hex, privateKey: PrivKey): Uint8Array;
+  function sign(message: Hex, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): Uint8Array;
-  function sign(message: G2, privateKey: PrivKey): G2;
+  function sign(message: G2, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): G2;
-  function sign(message: G2Hex, privateKey: PrivKey): Uint8Array | G2 {
+  function sign(message: G2Hex, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): Uint8Array | G2 {
-    const msgPoint = normP2Hash(message);
+    const msgPoint = normP2Hash(message, htfOpts);
     msgPoint.assertValidity();
     const sigPoint = msgPoint.multiply(G1.normalizePrivateKey(privateKey));
     if (message instanceof G2.Point) return sigPoint;
@@ -274,9 +278,14 @@ export function bls<Fp2, Fp6, Fp12>(
 
   // Checks if pairing of public key & hash is equal to pairing of generator & signature.
   // e(P, H(m)) == e(G, S)
-  function verify(signature: G2Hex, message: G2Hex, publicKey: G1Hex): boolean {
+  function verify(
+    signature: G2Hex,
+    message: G2Hex,
+    publicKey: G1Hex,
+    htfOpts?: htf.htfBasicOpts
+  ): boolean {
     const P = normP1(publicKey);
-    const Hm = normP2Hash(message);
+    const Hm = normP2Hash(message, htfOpts);
     const G = G1.Point.BASE;
     const S = normP2(signature);
     // Instead of doing 2 exponentiations, we use property of billinear maps
@@ -323,12 +332,17 @@ export function bls<Fp2, Fp6, Fp12>(
 
   // https://ethresear.ch/t/fast-verification-of-multiple-bls-signatures/5407
   // e(G, S) = e(G, SUM(n)(Si)) = MUL(n)(e(G, Si))
-  function verifyBatch(signature: G2Hex, messages: G2Hex[], publicKeys: G1Hex[]): boolean {
+  function verifyBatch(
+    signature: G2Hex,
+    messages: G2Hex[],
+    publicKeys: G1Hex[],
+    htfOpts?: htf.htfBasicOpts
+  ): boolean {
     if (!messages.length) throw new Error('Expected non-empty messages array');
     if (publicKeys.length !== messages.length)
       throw new Error('Pubkey count should equal msg count');
     const sig = normP2(signature);
-    const nMessages = messages.map(normP2Hash);
+    const nMessages = messages.map((i) => normP2Hash(i, htfOpts));
     const nPublicKeys = publicKeys.map(normP1);
     try {
       const paired = [];
@@ -365,6 +379,7 @@ export function bls<Fp2, Fp6, Fp12>(
     Signature,
     millerLoop,
     calcPairingPrecomputes,
+    hashToCurve: { G1: G1HashToCurve, G2: G2HashToCurve },
     pairing,
     getPublicKey,
     sign,

src/abstract/edwards.ts

@@ -13,7 +13,6 @@ import * as mod from './modular.js';
 import * as ut from './utils.js';
 import { ensureBytes, Hex, PrivKey } from './utils.js';
 import { Group, GroupConstructor, wNAF } from './group.js';
-import { hash_to_field as hashToField, htfOpts, validateHTFOpts } from './hash-to-curve.js';
 
 // Be friendly to bad ECMAScript parsers by not using bigint literals like 123n
 const _0n = BigInt(0);
@@ -39,8 +38,6 @@ export type CurveType = ut.BasicCurve<bigint> & {
   uvRatio?: (u: bigint, v: bigint) => { isValid: boolean; value: bigint };
   // RFC 8032 pre-hashing of messages to sign() / verify()
   preHash?: ut.CHash;
-  // Hash to field options
-  htfDefaults?: htfOpts;
   mapToCurve?: (scalar: bigint[]) => { x: bigint; y: bigint };
 };
 
@@ -59,7 +56,6 @@ function validateOpts(curve: CurveType) {
     if (opts[fn] === undefined) continue; // Optional
     if (typeof opts[fn] !== 'function') throw new Error(`Invalid ${fn} function`);
   }
-  if (opts.htfDefaults !== undefined) validateHTFOpts(opts.htfDefaults);
   // Set defaults
   return Object.freeze({ ...opts } as const);
 }
@@ -114,8 +110,6 @@ export interface PointConstructor extends GroupConstructor<PointType> {
   new (x: bigint, y: bigint): PointType;
   fromHex(hex: Hex): PointType;
   fromPrivateKey(privateKey: PrivKey): PointType;
-  hashToCurve(msg: Hex, options?: Partial<htfOpts>): PointType;
-  encodeToCurve(msg: Hex, options?: Partial<htfOpts>): PointType;
 }
 
 export type PubKey = Hex | PointType;
@@ -484,25 +478,6 @@ export function twistedEdwards(curveDef: CurveType): CurveFn {
     clearCofactor() {
       return ExtendedPoint.fromAffine(this).clearCofactor().toAffine();
     }
-    // Encodes byte string to elliptic curve
-    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-3
-    static hashToCurve(msg: Hex, options?: Partial<htfOpts>) {
-      const { mapToCurve, htfDefaults } = CURVE;
-      if (!mapToCurve) throw new Error('No mapToCurve defined for curve');
-      const u = hashToField(ensureBytes(msg), 2, { ...htfDefaults, ...options } as htfOpts);
-      const { x: x0, y: y0 } = mapToCurve(u[0]);
-      const { x: x1, y: y1 } = mapToCurve(u[1]);
-      const p = new Point(x0, y0).add(new Point(x1, y1)).clearCofactor();
-      return p;
-    }
-    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-16#section-3
-    static encodeToCurve(msg: Hex, options?: Partial<htfOpts>) {
-      const { mapToCurve, htfDefaults } = CURVE;
-      if (!mapToCurve) throw new Error('No mapToCurve defined for curve');
-      const u = hashToField(ensureBytes(msg), 1, { ...htfDefaults, ...options } as htfOpts);
-      const { x, y } = mapToCurve(u[0]);
-      return new Point(x, y).clearCofactor();
-    }
   }
 
   /**

src/abstract/hash-to-curve.ts

@@ -1,11 +1,13 @@
 /*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
-import { CHash, concatBytes } from './utils.js';
+import * as ut from './utils.js';
 import * as mod from './modular.js';
+import type { Group, GroupConstructor } from './group.js';
 
-export type htfOpts = {
+export type Opts = {
   // DST: a domain separation tag
   // defined in section 2.2.5
   DST: string;
+  encodeDST: string;
   // p: the characteristic of F
   //    where F is a finite field of characteristic p and order q = p^m
   p: bigint;
@@ -22,10 +24,10 @@ export type htfOpts = {
   // wide range of hash functions, including SHA-2, SHA-3, BLAKE2, and others.
   // BBS+ uses blake2: https://github.com/hyperledger/aries-framework-go/issues/2247
   // TODO: verify that hash is shake if expand==='xof' via types
-  hash: CHash;
+  hash: ut.CHash;
 };
 
-export function validateHTFOpts(opts: htfOpts) {
+export function validateOpts(opts: Opts) {
   if (typeof opts.DST !== 'string') throw new Error('Invalid htf/DST');
   if (typeof opts.p !== 'bigint') throw new Error('Invalid htf/p');
   if (typeof opts.m !== 'number') throw new Error('Invalid htf/m');
@@ -81,25 +83,25 @@ export function expand_message_xmd(
   msg: Uint8Array,
   DST: Uint8Array,
   lenInBytes: number,
-  H: CHash
+  H: ut.CHash
 ): Uint8Array {
   // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-16#section-5.3.3
-  if (DST.length > 255) DST = H(concatBytes(stringToBytes('H2C-OVERSIZE-DST-'), DST));
+  if (DST.length > 255) DST = H(ut.concatBytes(stringToBytes('H2C-OVERSIZE-DST-'), DST));
   const b_in_bytes = H.outputLen;
   const r_in_bytes = H.blockLen;
   const ell = Math.ceil(lenInBytes / b_in_bytes);
   if (ell > 255) throw new Error('Invalid xmd length');
-  const DST_prime = concatBytes(DST, i2osp(DST.length, 1));
+  const DST_prime = ut.concatBytes(DST, i2osp(DST.length, 1));
   const Z_pad = i2osp(0, r_in_bytes);
   const l_i_b_str = i2osp(lenInBytes, 2);
   const b = new Array<Uint8Array>(ell);
-  const b_0 = H(concatBytes(Z_pad, msg, l_i_b_str, i2osp(0, 1), DST_prime));
+  const b_0 = H(ut.concatBytes(Z_pad, msg, l_i_b_str, i2osp(0, 1), DST_prime));
-  b[0] = H(concatBytes(b_0, i2osp(1, 1), DST_prime));
+  b[0] = H(ut.concatBytes(b_0, i2osp(1, 1), DST_prime));
   for (let i = 1; i <= ell; i++) {
     const args = [strxor(b_0, b[i - 1]), i2osp(i + 1, 1), DST_prime];
-    b[i] = H(concatBytes(...args));
+    b[i] = H(ut.concatBytes(...args));
   }
-  const pseudo_random_bytes = concatBytes(...b);
+  const pseudo_random_bytes = ut.concatBytes(...b);
   return pseudo_random_bytes.slice(0, lenInBytes);
 }
 
@@ -108,7 +110,7 @@ export function expand_message_xof(
   DST: Uint8Array,
   lenInBytes: number,
   k: number,
-  H: CHash
+  H: ut.CHash
 ): Uint8Array {
   // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-16#section-5.3.3
   // DST = H('H2C-OVERSIZE-DST-' || a_very_long_DST, Math.ceil((lenInBytes * k) / 8));
@@ -137,7 +139,7 @@ export function expand_message_xof(
  * @param options `{DST: string, p: bigint, m: number, k: number, expand: 'xmd' | 'xof', hash: H}`
  * @returns [u_0, ..., u_(count - 1)], a list of field elements.
  */
-export function hash_to_field(msg: Uint8Array, count: number, options: htfOpts): bigint[][] {
+export function hash_to_field(msg: Uint8Array, count: number, options: Opts): bigint[][] {
   // if options is provided but incomplete, fill any missing fields with the
   // value in hftDefaults (ie hash to G2).
   const log2p = options.p.toString(2).length;
@@ -175,3 +177,48 @@ export function isogenyMap<T, F extends mod.Field<T>>(field: F, map: [T[], T[],
     return { x, y };
   };
 }
+
+export interface Point<T> extends Group<Point<T>> {
+  readonly x: T;
+  readonly y: T;
+  clearCofactor(): Point<T>;
+}
+
+export interface PointConstructor<T> extends GroupConstructor<Point<T>> {
+  new (x: T, y: T): Point<T>;
+}
+
+export type MapToCurve<T> = (scalar: bigint[]) => { x: T; y: T };
+
+// Separated from initialization opts, so users won't accidentally change per-curve parameters (changing DST is ok!)
+export type htfBasicOpts = {
+  DST: string;
+};
+
+export function hashToCurve<T>(Point: PointConstructor<T>, mapToCurve: MapToCurve<T>, def: Opts) {
+  validateOpts(def);
+  if (typeof mapToCurve !== 'function')
+    throw new Error('hashToCurve: mapToCurve() has not been defined');
+
+  return {
+    // Encodes byte string to elliptic curve
+    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-3
+    hashToCurve(msg: ut.Hex, options?: htfBasicOpts) {
+      if (!mapToCurve) throw new Error('CURVE.mapToCurve() has not been defined');
+      msg = ut.ensureBytes(msg);
+      const u = hash_to_field(msg, 2, { ...def, DST: def.DST, ...options } as Opts);
+      const { x: x0, y: y0 } = mapToCurve(u[0]);
+      const { x: x1, y: y1 } = mapToCurve(u[1]);
+      return new Point(x0, y0).add(new Point(x1, y1)).clearCofactor();
+    },
+
+    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-16#section-3
+    encodeToCurve(msg: ut.Hex, options?: htfBasicOpts) {
+      if (!mapToCurve) throw new Error('CURVE.mapToCurve() has not been defined');
+      msg = ut.ensureBytes(msg);
+      const u = hash_to_field(msg, 1, { ...def, DST: def.encodeDST, ...options } as Opts);
+      const { x, y } = mapToCurve(u[0]);
+      return new Point(x, y).clearCofactor();
+    },
+  };
+}

src/abstract/weierstrass.ts

@@ -11,7 +11,6 @@
 import * as mod from './modular.js';
 import * as ut from './utils.js';
 import { bytesToHex, Hex, PrivKey } from './utils.js';
-import { hash_to_field, htfOpts, validateHTFOpts } from './hash-to-curve.js';
 import { Group, GroupConstructor, wNAF } from './group.js';
 
 type HmacFnSync = (key: Uint8Array, ...messages: Uint8Array[]) => Uint8Array;
@@ -39,9 +38,6 @@ export type BasicCurve<T> = ut.BasicCurve<T> & {
     c: ProjectiveConstructor<T>,
     point: ProjectivePointType<T>
   ) => ProjectivePointType<T>;
-  // Hash to field options
-  htfDefaults?: htfOpts;
-  mapToCurve?: (scalar: bigint[]) => { x: T; y: T };
 };
 
 // ASN.1 DER encoding utilities
@@ -121,6 +117,7 @@ export interface ProjectivePointType<T> extends Group<ProjectivePointType<T>> {
   multiply(scalar: number | bigint, affinePoint?: PointType<T>): ProjectivePointType<T>;
   multiplyUnsafe(scalar: bigint): ProjectivePointType<T>;
   toAffine(invZ?: T): PointType<T>;
+  clearCofactor(): ProjectivePointType<T>;
 }
 // Static methods for 3d XYZ points
 export interface ProjectiveConstructor<T> extends GroupConstructor<ProjectivePointType<T>> {
@@ -139,14 +136,13 @@ export interface PointType<T> extends Group<PointType<T>> {
   toHex(isCompressed?: boolean): string;
   assertValidity(): void;
   multiplyAndAddUnsafe(Q: PointType<T>, a: bigint, b: bigint): PointType<T> | undefined;
+  clearCofactor(): PointType<T>;
 }
 // Static methods for 2d XY points
 export interface PointConstructor<T> extends GroupConstructor<PointType<T>> {
   new (x: T, y: T): PointType<T>;
   fromHex(hex: Hex): PointType<T>;
   fromPrivateKey(privateKey: PrivKey): PointType<T>;
-  hashToCurve(msg: Hex, options?: Partial<htfOpts>): PointType<T>;
-  encodeToCurve(msg: Hex, options?: Partial<htfOpts>): PointType<T>;
 }
 
 export type CurvePointsType<T> = BasicCurve<T> & {
@@ -162,7 +158,7 @@ function validatePointOpts<T>(curve: CurvePointsType<T>) {
     if (!Fp.isValid(curve[i]))
       throw new Error(`Invalid curve param ${i}=${opts[i]} (${typeof opts[i]})`);
   }
-  for (const i of ['isTorsionFree', 'clearCofactor', 'mapToCurve'] as const) {
+  for (const i of ['isTorsionFree', 'clearCofactor'] as const) {
     if (curve[i] === undefined) continue; // Optional
     if (typeof curve[i] !== 'function') throw new Error(`Invalid ${i} function`);
   }
@@ -181,8 +177,6 @@ function validatePointOpts<T>(curve: CurvePointsType<T>) {
   }
   if (typeof opts.fromBytes !== 'function') throw new Error('Invalid fromBytes function');
   if (typeof opts.toBytes !== 'function') throw new Error('Invalid fromBytes function');
-  // Requires including hashToCurve file
-  if (opts.htfDefaults !== undefined) validateHTFOpts(opts.htfDefaults);
   // Set defaults
   return Object.freeze({ ...opts } as const);
 }
@@ -671,28 +665,6 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
       const sum = aP.add(bQ);
       return sum.equals(ProjectivePoint.ZERO) ? undefined : sum.toAffine();
     }
-
-    // Encodes byte string to elliptic curve
-    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-3
-    static hashToCurve(msg: Hex, options?: Partial<htfOpts>) {
-      const { mapToCurve } = CURVE;
-      if (!mapToCurve) throw new Error('CURVE.mapToCurve() has not been defined');
-      msg = ut.ensureBytes(msg);
-      const u = hash_to_field(msg, 2, { ...CURVE.htfDefaults, ...options } as htfOpts);
-      const { x: x0, y: y0 } = mapToCurve(u[0]);
-      const { x: x1, y: y1 } = mapToCurve(u[1]);
-      return new Point(x0, y0).add(new Point(x1, y1)).clearCofactor();
-    }
-
-    // https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-16#section-3
-    static encodeToCurve(msg: Hex, options?: Partial<htfOpts>) {
-      const { mapToCurve } = CURVE;
-      if (!mapToCurve) throw new Error('CURVE.mapToCurve() has not been defined');
-      msg = ut.ensureBytes(msg);
-      const u = hash_to_field(msg, 1, { ...CURVE.htfDefaults, ...options } as htfOpts);
-      const { x, y } = mapToCurve(u[0]);
-      return new Point(x, y).clearCofactor();
-    }
   }
 
   return {

src/bls12-381.ts

@@ -920,6 +920,7 @@ const htfDefaults = {
   // defined in section 2.2.5
   // Use utils.getDSTLabel(), utils.setDSTLabel(value)
   DST: 'BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_',
+  encodeDST: 'BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_',
   // p: the characteristic of F
   //    where F is a finite field of characteristic p and order q = p^m
   p: Fp.ORDER,

src/ed25519.ts

@@ -12,6 +12,7 @@ import {
   numberToBytesLE,
   Hex,
 } from './abstract/utils.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 /**
  * ed25519 Twisted Edwards curve with following addons:
@@ -189,15 +190,6 @@ const ED25519_DEF = {
   // Ratio of u to v. Allows us to combine inversion and square root. Uses algo from RFC8032 5.1.3.
   // Constant-time, u/√v
   uvRatio,
-  htfDefaults: {
-    DST: 'edwards25519_XMD:SHA-512_ELL2_RO_',
-    p: Fp.ORDER,
-    m: 1,
-    k: 128,
-    expand: 'xmd',
-    hash: sha512,
-  },
-  mapToCurve: (scalars: bigint[]) => map_to_curve_elligator2_edwards25519(scalars[0]),
 } as const;
 
 export const ed25519 = twistedEdwards(ED25519_DEF);
@@ -217,6 +209,21 @@ export const ed25519ph = twistedEdwards({
   preHash: sha512,
 });
 
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  ed25519.Point,
+  (scalars: bigint[]) => map_to_curve_elligator2_edwards25519(scalars[0]),
+  {
+    DST: 'edwards25519_XMD:SHA-512_ELL2_RO_',
+    encodeDST: 'edwards25519_XMD:SHA-512_ELL2_NU_',
+    p: Fp.ORDER,
+    m: 1,
+    k: 128,
+    expand: 'xmd',
+    hash: sha512,
+  }
+);
+export { hashToCurve, encodeToCurve };
+
 export const x25519 = montgomery({
   P: ED25519_P,
   a24: BigInt('121665'),

src/ed448.ts

@@ -4,6 +4,7 @@ import { concatBytes, randomBytes, utf8ToBytes, wrapConstructor } from '@noble/h
 import { twistedEdwards } from './abstract/edwards.js';
 import { mod, pow2, Fp as Field } from './abstract/modular.js';
 import { montgomery } from './abstract/montgomery.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 /**
  * Edwards448 (not Ed448-Goldilocks) curve with following addons:
@@ -189,21 +190,27 @@ const ED448_DEF = {
     // square root exists, and the decoding fails.
     return { isValid: mod(x2 * v, P) === u, value: x };
   },
-  htfDefaults: {
-    DST: 'edwards448_XOF:SHAKE256_ELL2_RO_',
-    p: Fp.ORDER,
-    m: 1,
-    k: 224,
-    expand: 'xof',
-    hash: shake256,
-  },
-  mapToCurve: (scalars: bigint[]) => map_to_curve_elligator2_edwards448(scalars[0]),
 } as const;
 
 export const ed448 = twistedEdwards(ED448_DEF);
 // NOTE: there is no ed448ctx, since ed448 supports ctx by default
 export const ed448ph = twistedEdwards({ ...ED448_DEF, preHash: shake256_64 });
 
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  ed448.Point,
+  (scalars: bigint[]) => map_to_curve_elligator2_edwards448(scalars[0]),
+  {
+    DST: 'edwards448_XOF:SHAKE256_ELL2_RO_',
+    encodeDST: 'edwards448_XOF:SHAKE256_ELL2_NU_',
+    p: Fp.ORDER,
+    m: 1,
+    k: 224,
+    expand: 'xof',
+    hash: shake256,
+  }
+);
+export { hashToCurve, encodeToCurve };
+
 export const x448 = montgomery({
   a24: BigInt(39081),
   montgomeryBits: 448,

src/p256.ts

@@ -3,6 +3,7 @@ import { createCurve } from './_shortw_utils.js';
 import { sha256 } from '@noble/hashes/sha256';
 import { Fp as Field } from './abstract/modular.js';
 import { mapToCurveSimpleSWU } from './abstract/weierstrass.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 // NIST secp256r1 aka P256
 // https://www.secg.org/sec2-v2.pdf, https://neuromancer.sk/std/nist/P-256
@@ -31,16 +32,22 @@ export const P256 = createCurve(
     Gy: BigInt('0x4fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5'),
     h: BigInt(1),
     lowS: false,
-    mapToCurve: (scalars: bigint[]) => mapSWU(scalars[0]),
-    htfDefaults: {
-      DST: 'P256_XMD:SHA-256_SSWU_RO_',
-      p: Fp.ORDER,
-      m: 1,
-      k: 128,
-      expand: 'xmd',
-      hash: sha256,
-    },
   } as const,
   sha256
 );
 export const secp256r1 = P256;
+
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  secp256r1.Point,
+  (scalars: bigint[]) => mapSWU(scalars[0]),
+  {
+    DST: 'P256_XMD:SHA-256_SSWU_RO_',
+    encodeDST: 'P256_XMD:SHA-256_SSWU_NU_',
+    p: Fp.ORDER,
+    m: 1,
+    k: 128,
+    expand: 'xmd',
+    hash: sha256,
+  }
+);
+export { hashToCurve, encodeToCurve };

src/p384.ts

@@ -3,6 +3,7 @@ import { createCurve } from './_shortw_utils.js';
 import { sha384 } from '@noble/hashes/sha512';
 import { Fp as Field } from './abstract/modular.js';
 import { mapToCurveSimpleSWU } from './abstract/weierstrass.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 // NIST secp384r1 aka P384
 // https://www.secg.org/sec2-v2.pdf, https://neuromancer.sk/std/nist/P-384
@@ -35,16 +36,22 @@ export const P384 = createCurve({
     Gy: BigInt('0x3617de4a96262c6f5d9e98bf9292dc29f8f41dbd289a147ce9da3113b5f0b8c00a60b1ce1d7e819d7a431d7c90ea0e5f'),
     h: BigInt(1),
     lowS: false,
-    mapToCurve: (scalars: bigint[]) => mapSWU(scalars[0]),
-    htfDefaults: {
-      DST: 'P384_XMD:SHA-384_SSWU_RO_',
-      p: Fp.ORDER,
-      m: 1,
-      k: 192,
-      expand: 'xmd',
-      hash: sha384,
-    },
   } as const,
   sha384
 );
 export const secp384r1 = P384;
+
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  secp384r1.Point,
+  (scalars: bigint[]) => mapSWU(scalars[0]),
+  {
+    DST: 'P384_XMD:SHA-384_SSWU_RO_',
+    encodeDST: 'P384_XMD:SHA-384_SSWU_NU_',
+    p: Fp.ORDER,
+    m: 1,
+    k: 192,
+    expand: 'xmd',
+    hash: sha384,
+  }
+);
+export { hashToCurve, encodeToCurve };

src/p521.ts

@@ -4,6 +4,7 @@ import { sha512 } from '@noble/hashes/sha512';
 import { bytesToHex, PrivKey } from './abstract/utils.js';
 import { Fp as Field } from './abstract/modular.js';
 import { mapToCurveSimpleSWU } from './abstract/weierstrass.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 // NIST secp521r1 aka P521
 // Note that it's 521, which differs from 512 of its hash function.
@@ -48,14 +49,20 @@ export const P521 = createCurve({
     }
     return key.padStart(66 * 2, '0');
   },
-  mapToCurve: (scalars: bigint[]) => mapSWU(scalars[0]),
+} as const, sha512);
-  htfDefaults: {
+export const secp521r1 = P521;
+
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  secp521r1.Point,
+  (scalars: bigint[]) => mapSWU(scalars[0]),
+  {
     DST: 'P521_XMD:SHA-512_SSWU_RO_',
+    encodeDST: 'P521_XMD:SHA-512_SSWU_NU_',
     p: Fp.ORDER,
     m: 1,
     k: 256,
-      expand: 'xmd',
+    expand: 'xmd',
     hash: sha512,
-  },
+  }
-} as const, sha512);
+);
-export const secp521r1 = P521;
+export { hashToCurve, encodeToCurve };

src/secp256k1.ts

@@ -12,7 +12,7 @@ import {
   PrivKey,
 } from './abstract/utils.js';
 import { randomBytes } from '@noble/hashes/utils';
-import { isogenyMap } from './abstract/hash-to-curve.js';
+import * as htf from './abstract/hash-to-curve.js';
 
 /**
  * secp256k1 belongs to Koblitz curves: it has efficiently computable endomorphism.
@@ -62,7 +62,7 @@ function sqrtMod(y: bigint): bigint {
 const Fp = Field(secp256k1P, undefined, undefined, { sqrt: sqrtMod });
 type Fp = bigint;
 
-const isoMap = isogenyMap(
+const isoMap = htf.isogenyMap(
   Fp,
   [
     // xNum
@@ -143,22 +143,28 @@ export const secp256k1 = createCurve(
         return { k1neg, k1, k2neg, k2 };
       },
     },
-    mapToCurve: (scalars: bigint[]) => {
-      const { x, y } = mapSWU(Fp.create(scalars[0]));
-      return isoMap(x, y);
-    },
-    htfDefaults: {
-      DST: 'secp256k1_XMD:SHA-256_SSWU_RO_',
-      p: Fp.ORDER,
-      m: 1,
-      k: 128,
-      expand: 'xmd',
-      hash: sha256,
-    },
   },
   sha256
 );
 
+const { hashToCurve, encodeToCurve } = htf.hashToCurve(
+  secp256k1.Point,
+  (scalars: bigint[]) => {
+    const { x, y } = mapSWU(Fp.create(scalars[0]));
+    return isoMap(x, y);
+  },
+  {
+    DST: 'secp256k1_XMD:SHA-256_SSWU_RO_',
+    encodeDST: 'secp256k1_XMD:SHA-256_SSWU_NU_',
+    p: Fp.ORDER,
+    m: 1,
+    k: 128,
+    expand: 'xmd',
+    hash: sha256,
+  }
+);
+export { hashToCurve, encodeToCurve };
+
 // Schnorr
 const _0n = BigInt(0);
 const numTo32b = secp256k1.utils._bigintToBytes;

test/bls12-381.test.js

@@ -1459,8 +1459,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G1.length; i++) {
     const t = VECTORS_G1[i];
-    should(`hashToCurve/G1 Killic (${i})`, async () => {
+    should(`hashToCurve/G1 Killic (${i})`, () => {
-      const p = await bls.G1.Point.hashToCurve(t.msg, {
+      const p = bls.hashToCurve.G1.hashToCurve(t.msg, {
         DST: 'BLS12381G1_XMD:SHA-256_SSWU_RO_TESTGEN',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1514,8 +1514,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G1_RO.length; i++) {
     const t = VECTORS_G1_RO[i];
-    should(`hashToCurve/G1 (BLS12381G1_XMD:SHA-256_SSWU_RO_) (${i})`, async () => {
+    should(`hashToCurve/G1 (BLS12381G1_XMD:SHA-256_SSWU_RO_) (${i})`, () => {
-      const p = await bls.G1.Point.hashToCurve(t.msg, {
+      const p = bls.hashToCurve.G1.hashToCurve(t.msg, {
         DST: 'QUUX-V01-CS02-with-BLS12381G1_XMD:SHA-256_SSWU_RO_',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1560,8 +1560,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G1_NU.length; i++) {
     const t = VECTORS_G1_NU[i];
-    should(`hashToCurve/G1 (BLS12381G1_XMD:SHA-256_SSWU_NU_) (${i})`, async () => {
+    should(`hashToCurve/G1 (BLS12381G1_XMD:SHA-256_SSWU_NU_) (${i})`, () => {
-      const p = await bls.G1.Point.encodeToCurve(t.msg, {
+      const p = bls.hashToCurve.G1.encodeToCurve(t.msg, {
         DST: 'QUUX-V01-CS02-with-BLS12381G1_XMD:SHA-256_SSWU_NU_',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1597,8 +1597,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_ENCODE_G1.length; i++) {
     const t = VECTORS_ENCODE_G1[i];
-    should(`hashToCurve/G1 (Killic, encodeToCurve) (${i})`, async () => {
+    should(`hashToCurve/G1 (Killic, encodeToCurve) (${i})`, () => {
-      const p = await bls.G1.Point.encodeToCurve(t.msg, {
+      const p = bls.hashToCurve.G1.encodeToCurve(t.msg, {
         DST: 'BLS12381G1_XMD:SHA-256_SSWU_NU_TESTGEN',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1643,8 +1643,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G2.length; i++) {
     const t = VECTORS_G2[i];
-    should(`hashToCurve/G2 Killic (${i})`, async () => {
+    should(`hashToCurve/G2 Killic (${i})`, () => {
-      const p = await bls.G2.Point.hashToCurve(t.msg, {
+      const p = bls.hashToCurve.G2.hashToCurve(t.msg, {
         DST: 'BLS12381G2_XMD:SHA-256_SSWU_RO_TESTGEN',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1708,8 +1708,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G2_RO.length; i++) {
     const t = VECTORS_G2_RO[i];
-    should(`hashToCurve/G2 (BLS12381G2_XMD:SHA-256_SSWU_RO_) (${i})`, async () => {
+    should(`hashToCurve/G2 (BLS12381G2_XMD:SHA-256_SSWU_RO_) (${i})`, () => {
-      const p = await bls.G2.Point.hashToCurve(t.msg, {
+      const p = bls.hashToCurve.G2.hashToCurve(t.msg, {
         DST: 'QUUX-V01-CS02-with-BLS12381G2_XMD:SHA-256_SSWU_RO_',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1773,8 +1773,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_G2_NU.length; i++) {
     const t = VECTORS_G2_NU[i];
-    should(`hashToCurve/G2 (BLS12381G2_XMD:SHA-256_SSWU_NU_) (${i})`, async () => {
+    should(`hashToCurve/G2 (BLS12381G2_XMD:SHA-256_SSWU_NU_) (${i})`, () => {
-      const p = await bls.G2.Point.encodeToCurve(t.msg, {
+      const p = bls.hashToCurve.G2.encodeToCurve(t.msg, {
         DST: 'QUUX-V01-CS02-with-BLS12381G2_XMD:SHA-256_SSWU_NU_',
       });
       deepStrictEqual(p.toHex(), t.expected);
@@ -1818,8 +1818,8 @@ describe('hash-to-curve', () => {
   ];
   for (let i = 0; i < VECTORS_ENCODE_G2.length; i++) {
     const t = VECTORS_ENCODE_G2[i];
-    should(`hashToCurve/G2 (Killic, encodeToCurve) (${i})`, async () => {
+    should(`hashToCurve/G2 (Killic, encodeToCurve) (${i})`, () => {
-      const p = await bls.G2.Point.encodeToCurve(t.msg, {
+      const p = bls.hashToCurve.G2.encodeToCurve(t.msg, {
         DST: 'BLS12381G2_XMD:SHA-256_SSWU_NU_TESTGEN',
       });
       deepStrictEqual(p.toHex(), t.expected);

test/hash-to-curve.test.js

@@ -5,12 +5,12 @@ import { bytesToHex } from '@noble/hashes/utils';
 import { sha256 } from '@noble/hashes/sha256';
 import { sha512 } from '@noble/hashes/sha512';
 import { shake128, shake256 } from '@noble/hashes/sha3';
-import { secp256r1 } from '../lib/esm/p256.js';
+import * as secp256r1 from '../lib/esm/p256.js';
-import { secp384r1 } from '../lib/esm/p384.js';
+import * as secp384r1 from '../lib/esm/p384.js';
-import { secp521r1 } from '../lib/esm/p521.js';
+import * as secp521r1 from '../lib/esm/p521.js';
-import { ed25519 } from '../lib/esm/ed25519.js';
+import * as ed25519 from '../lib/esm/ed25519.js';
-import { ed448 } from '../lib/esm/ed448.js';
+import * as ed448 from '../lib/esm/ed448.js';
-import { secp256k1 } from '../lib/esm/secp256k1.js';
+import * as secp256k1 from '../lib/esm/secp256k1.js';
 import { bls12_381 } from '../lib/esm/bls12-381.js';
 import {
   stringToBytes,
@@ -111,7 +111,7 @@ function testCurve(curve, ro, nu) {
     for (let i = 0; i < ro.vectors.length; i++) {
       const t = ro.vectors[i];
       should(`(${i})`, () => {
-        const p = curve.Point.hashToCurve(stringToBytes(t.msg), {
+        const p = curve.hashToCurve(stringToBytes(t.msg), {
           DST: ro.dst,
         });
         deepStrictEqual(p.x, stringToFp(t.P.x), 'Px');
@@ -123,7 +123,7 @@ function testCurve(curve, ro, nu) {
     for (let i = 0; i < nu.vectors.length; i++) {
       const t = nu.vectors[i];
       should(`(${i})`, () => {
-        const p = curve.Point.encodeToCurve(stringToBytes(t.msg), {
+        const p = curve.encodeToCurve(stringToBytes(t.msg), {
           DST: nu.dst,
         });
         deepStrictEqual(p.x, stringToFp(t.P.x), 'Px');
@@ -137,8 +137,8 @@ testCurve(secp256r1, p256_ro, p256_nu);
 testCurve(secp384r1, p384_ro, p384_nu);
 testCurve(secp521r1, p521_ro, p521_nu);
 // TODO: remove same tests from bls12
-testCurve(bls12_381.G1, g1_ro, g1_nu);
+testCurve(bls12_381.hashToCurve.G1, g1_ro, g1_nu);
-testCurve(bls12_381.G2, g2_ro, g2_nu);
+testCurve(bls12_381.hashToCurve.G2, g2_ro, g2_nu);
 testCurve(secp256k1, secp256k1_ro, secp256k1_nu);
 testCurve(ed25519, ed25519_ro, ed25519_nu);
 testCurve(ed448, ed448_ro, ed448_nu);

test/stark/stark.test.js

@@ -255,7 +255,7 @@ should('Starknet.js cross-tests', () => {
   );
   const msgHash = '0x6d1706bd3d1ba7c517be2a2a335996f63d4738e2f182144d078a1dd9997062e';
   const sig = starknet.sign(msgHash, privateKey);
-  const { r, s } = (sig);
+  const { r, s } = sig;
 
   deepStrictEqual(
     r.toString(),