@shard-auth/client/dist/frost/math.js

Next-generation API authentication without secret keys - MPC-based authentication with FROST threshold signatures

"use strict";
/**
 * FROST数学的演算
 * 定数時間実装でタイミング攻撃を防ぐ
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.randomBytes = randomBytes;
exports.computeLagrangeCoefficient = computeLagrangeCoefficient;
exports.hash = hash;
exports.evaluatePolynomial = evaluatePolynomial;
exports.generatePolynomialCoefficients = generatePolynomialCoefficients;
exports.constantTimeEqual = constantTimeEqual;
const secp256k1_1 = require("@noble/curves/secp256k1");
const sha256_1 = require("@noble/hashes/sha256");
const crypto_1 = require("crypto");
// 定数時間のランダムバイト生成
function randomBytes(length) {
    return Buffer.from((0, crypto_1.randomBytes)(length));
}
// Lagrange補間の係数を計算
function computeLagrangeCoefficient(participantIndex, participantIndices) {
    const order = secp256k1_1.secp256k1.CURVE.n;
    let numerator = 1n;
    let denominator = 1n;
    for (const j of participantIndices) {
        if (j === participantIndex)
            continue;
        numerator = (numerator * BigInt(-j)) % order;
        denominator = (denominator * BigInt(participantIndex - j)) % order;
    }
    // モジュラー逆元を計算
    const denominatorInv = modInverse(denominator, order);
    return (numerator * denominatorInv) % order;
}
// モジュラー逆元（拡張ユークリッド互除法）
function modInverse(a, m) {
    let [old_r, r] = [a, m];
    let [old_s, s] = [1n, 0n];
    while (r !== 0n) {
        const quotient = old_r / r;
        [old_r, r] = [r, old_r - quotient * r];
        [old_s, s] = [s, old_s - quotient * s];
    }
    return ((old_s % m) + m) % m;
}
// ハッシュ関数（ドメイン分離付き）
function hash(domain, ...inputs) {
    const domainSeparator = Buffer.from(domain, 'utf8');
    const allInputs = [domainSeparator, ...inputs];
    const concatenated = Buffer.concat(allInputs);
    return Buffer.from((0, sha256_1.sha256)(concatenated));
}
// 多項式評価
function evaluatePolynomial(coefficients, x, order) {
    let result = 0n;
    let xPower = 1n;
    for (const coeff of coefficients) {
        result = (result + coeff * xPower) % order;
        xPower = (xPower * x) % order;
    }
    return ((result % order) + order) % order;
}
// シェア生成用の多項式係数を生成
function generatePolynomialCoefficients(secret, threshold, order) {
    const coefficients = [secret];
    for (let i = 1; i < threshold; i++) {
        const randomCoeff = BigInt('0x' + randomBytes(32).toString('hex')) % order;
        coefficients.push(randomCoeff);
    }
    return coefficients;
}
// 定数時間比較
function constantTimeEqual(a, b) {
    if (a.length !== b.length)
        return false;
    let result = 0;
    for (let i = 0; i < a.length; i++) {
        result |= a[i] ^ b[i];
    }
    return result === 0;
}
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