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weierstrass: improve error wording for sqrt case

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Paul Miller 2023-12-13 12:58:51 +00:00
parent 4007ee975b
commit b39b0d1daf
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1 changed files with 7 additions and 1 deletions
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8
src/abstract/weierstrass.ts
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@ -733,7 +733,13 @@ export function weierstrass(curveDef: CurveType): CurveFn {
const x = ut.bytesToNumberBE(tail);
if (!isValidFieldElement(x)) throw new Error('Point is not on curve');
const y2 = weierstrassEquation(x); // y² = x³ + ax + b
let y = Fp.sqrt(y2); // y = y² ^ (p+1)/4
let y: bigint;
try {
y = Fp.sqrt(y2); // y = y² ^ (p+1)/4
} catch (sqrtError) {
const suffix = sqrtError instanceof Error ? ': ' + sqrtError.message : '';
throw new Error('Point is not on curve' + suffix);
}
const isYOdd = (y & _1n) === _1n;
// ECDSA
const isHeadOdd = (head & 1) === 1;