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hash-to-curve small refactor

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Paul Miller 2023-02-06 19:50:51 +00:00
parent cef4b52d12
commit 00b73b68d3
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1 changed files with 18 additions and 33 deletions
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51
src/abstract/hash-to-curve.ts
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@ -1,25 +1,15 @@
/*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
import type { Group, GroupConstructor, AffinePoint } from './curve.js';
import { mod, Field } from './modular.js';
import { CHash, Hex, concatBytes, ensureBytes } from './utils.js';
import { CHash, Hex, concatBytes, ensureBytes, validateObject } from './utils.js';
export type Opts = {
// DST: a domain separation tag
// defined in section 2.2.5
DST: string;
DST: string; // DST: a domain separation tag, defined in section 2.2.5
encodeDST: string;
// p: the characteristic of F
// where F is a finite field of characteristic p and order q = p^m
p: bigint;
// m: the extension degree of F, m >= 1
// where F is a finite field of characteristic p and order q = p^m
m: number;
// k: the target security level for the suite in bits
// defined in section 5.1
k: number;
// option to use a message that has already been processed by
// expand_message_xmd
expand?: 'xmd' | 'xof';
p: bigint; // characteristic of F, where F is a finite field of characteristic p and order q = p^m
m: number; // extension degree of F, m >= 1
k: number; // k: the target security level for the suite in bits, defined in section 5.1
expand?: 'xmd' | 'xof'; // use a message that has already been processed by expand_message_xmd
// Hash functions for: expand_message_xmd is appropriate for use with a
// 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
@ -27,17 +17,6 @@ export type Opts = {
hash: CHash;
};
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');
if (typeof opts.k !== 'number') throw new Error('Invalid htf/k');
if (opts.expand !== 'xmd' && opts.expand !== 'xof' && opts.expand !== undefined)
throw new Error('Invalid htf/expand');
if (typeof opts.hash !== 'function' || !Number.isSafeInteger(opts.hash.outputLen))
throw new Error('Invalid htf/hash function');
}
// Global symbols in both browsers and Node.js since v11
// See https://github.com/microsoft/TypeScript/issues/31535
declare const TextEncoder: any;
@ -195,20 +174,26 @@ export interface H2CPointConstructor<T> extends GroupConstructor<H2CPoint<T>> {
export type MapToCurve<T> = (scalar: bigint[]) => AffinePoint<T>;
// Separated from initialization opts, so users won't accidentally change per-curve parameters (changing DST is ok!)
export type htfBasicOpts = {
DST: string;
};
// 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: H2CPointConstructor<T>,
mapToCurve: MapToCurve<T>,
def: Opts
) {
validateOpts(def);
validateObject(def, {
DST: 'string',
p: 'bigint',
m: 'isSafeInteger',
k: 'isSafeInteger',
hash: 'hash',
});
if (def.expand !== 'xmd' && def.expand !== 'xof' && def.expand !== undefined)
throw new Error('Invalid htf/expand');
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