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weierstrass: make weierstrassPoints fromBytes / toBytes optional

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Paul Miller 2023-03-21 04:51:10 +00:00
parent a8b8192714
commit f3c21eb347
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GPG Key ID: 697079DA6878B89B
1 changed files with 24 additions and 7 deletions
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31
src/abstract/weierstrass.ts
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@ -82,8 +82,8 @@ export interface ProjConstructor<T> extends GroupConstructor<ProjPointType<T>> {
export type CurvePointsType<T> = BasicWCurve<T> & {
// Bytes
fromBytes: (bytes: Uint8Array) => AffinePoint<T>;
toBytes: (c: ProjConstructor<T>, point: ProjPointType<T>, compressed: boolean) => Uint8Array;
fromBytes?: (bytes: Uint8Array) => AffinePoint<T>;
toBytes?: (c: ProjConstructor<T>, point: ProjPointType<T>, isCompressed: boolean) => Uint8Array;
};
function validatePointOpts<T>(curve: CurvePointsType<T>) {
@ -93,8 +93,6 @@ function validatePointOpts<T>(curve: CurvePointsType<T>) {
{
a: 'field',
b: 'field',
fromBytes: 'function',
toBytes: 'function',
},
{
allowedPrivateKeyLengths: 'array',
@ -102,6 +100,8 @@ function validatePointOpts<T>(curve: CurvePointsType<T>) {
isTorsionFree: 'function',
clearCofactor: 'function',
allowInfinityPoint: 'boolean',
fromBytes: 'function',
toBytes: 'function',
}
);
const { endo, Fp, a } = opts;
@ -184,6 +184,23 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
const CURVE = validatePointOpts(opts);
const { Fp } = CURVE; // All curves has same field / group length as for now, but they can differ
const toBytes =
CURVE.toBytes ||
((c: ProjConstructor<T>, point: ProjPointType<T>, isCompressed: boolean) => {
const a = point.toAffine();
return ut.concatBytes(Uint8Array.from([0x04]), Fp.toBytes(a.x), Fp.toBytes(a.y));
});
const fromBytes =
CURVE.fromBytes ||
((bytes: Uint8Array) => {
// const head = bytes[0];
const tail = bytes.subarray(1);
// if (head !== 0x04) throw new Error('Only non-compressed encoding is supported');
const x = Fp.fromBytes(tail.subarray(0, Fp.BYTES));
const y = Fp.fromBytes(tail.subarray(Fp.BYTES, 2 * Fp.BYTES));
return { x, y };
});
/**
* y² = x³ + ax + b: Short weierstrass curve formula
* @returns y²
@ -280,7 +297,7 @@ 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('pointHex', hex)));
const P = Point.fromAffine(fromBytes(ensureBytes('pointHex', hex)));
P.assertValidity();
return P;
}
@ -563,7 +580,7 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
toRawBytes(isCompressed = true): Uint8Array {
this.assertValidity();
return CURVE.toBytes(Point, this, isCompressed);
return toBytes(Point, this, isCompressed);
}
toHex(isCompressed = true): string {
@ -574,6 +591,7 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>) {
const wnaf = wNAF(Point, CURVE.endo ? Math.ceil(_bits / 2) : _bits);
return {
CURVE,
ProjectivePoint: Point as ProjConstructor<T>,
normPrivateKeyToScalar,
weierstrassEquation,
@ -1055,7 +1073,6 @@ export function weierstrass(curveDef: CurveType): CurveFn {
}
// Implementation of the Shallue and van de Woestijne method for any Weierstrass curve
// TODO: check if there is a way to merge this with uvRatio in Edwards && move to modular?
// b = True and y = sqrt(u / v) if (u / v) is square in F, and
// b = False and y = sqrt(Z * (u / v)) otherwise.