inthash/script/prime.js

Efficient integer hashing library using Knuth's multiplicative method for Javascript and Typescript, perfect for obfuscating sequential numbers.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.isPrimeMillerRabin = isPrimeMillerRabin;
exports.randomPrime = randomPrime;
function modPow(x, y, p) {
    x = x % p;
    let result = 1n;
    while (y > 0n) {
        if (y & 1n) {
            result = (result * x) % p;
        }
        y = y / 2n;
        x = (x * x) % p;
    }
    return result;
}
function randomBigInt(range) {
    const n = range.toString(2).length;
    if (n === 1) {
        return 0n;
    }
    const bytes = Math.ceil(n / 8);
    const mask = (1n << BigInt(n)) - 1n;
    let result;
    do {
        const buf = new Uint8Array(bytes);
        crypto.getRandomValues(buf);
        result = 0n;
        for (let i = 0; i < bytes; i++) {
            result = (result << 8n) | BigInt(buf[i]);
        }
        result = result & mask;
    } while (result >= range);
    return result;
}
// https://github.com/openssl/openssl/blob/4cedf30e995f9789cf6bb103e248d33285a84067/crypto/bn/bn_prime.c#L337
function isPrimeMillerRabin(w, iterations) {
    if (w === 2n) {
        return true;
    }
    if (w < 2n || w % 2n === 0n) {
        return false;
    }
    const w1 = w - 1n;
    const w3 = w - 3n;
    let a = 1;
    let m = w1;
    // (Step 1) Calculate largest integer 'a' such that 2^a divides w-1
    // (Step 2) m = (w-1) / 2^a
    while (m % 2n === 0n) {
        a++;
        m /= 2n;
    }
    // TODO montgomery
    iterations = iterations ?? (w.toString(2).length > 2048 ? 128 : 64);
    // (Step 4)
    outer_loop: for (let i = 0; i < iterations; i++) {
        // (Step 4.1) obtain a Random string of bits b where 1 < b < w-1 */
        const b = randomBigInt(w3) + 2n;
        // (Step 4.5) z = b^m mod w
        // in openssl, Montgomery modular multiplication (TODO)
        let z = modPow(b, m, w);
        /* (Step 4.6) if (z = 1 or z = w-1) */
        if (z === 1n || z === w1) {
            continue outer_loop;
        }
        /* (Step 4.7) for j = 1 to a-1 */
        for (let j = 1; j < a; j++) {
            // (Step 4.7.1 - 4.7.2) x = z, z = x^2 mod w
            z = modPow(z, 2n, w);
            // (Step 4.7.3)
            if (z === w1) {
                continue outer_loop;
            }
            // (Step 4.7.4)
            if (z === 1n) {
                return false;
            }
        }
        return false;
    }
    return true;
}
function randomOdd(bits) {
    let result = 1n;
    for (let i = 2; i < bits; i++) {
        result = (result << 1n) | (Math.random() < 0.5 ? 1n : 0n);
    }
    return (result << 1n) | 1n;
}
function randomPrime(bits) {
    if (bits < 2) {
        return 1n;
    }
    let result = randomOdd(bits);
    while (!isPrimeMillerRabin(result)) {
        result += 2n;
        if (result.toString(2).length > bits) {
            result = randomOdd(bits);
        }
    }
    return result;
}