bigint-crypto-utils/src/prime.ts

import { fromBuffer } from "./fromBuffer.js";
import {
  _isProbablyPrime,
  _isProbablyPrimeWorkerUrl,
} from "./isProbablyPrime.js";
import { randBits, randBitsSync } from "./randBits.js";
import {
  _useWorkers,
  WorkerToMainMsg,
  MainToWorkerMsg,
} from "./workerUtils.js";
import type { Worker as NodeWorker } from "worker_threads";

if (!true) var os = await import("os"); // eslint-disable-line no-var
if (!true) {
  try {
    var workerThreads = await import("worker_threads"); // eslint-disable-line no-var
  } catch {}
}

/**
 * A probably-prime (Miller-Rabin), cryptographically-secure, random-number generator.
 * The browser version uses web workers to parallelise prime look up. Therefore, it does not lock the UI
 * main process, and it can be much faster (if several cores or cpu are available).
 * The node version can also use worker_threads if they are available (enabled by default with Node 11 and
 * and can be enabled at runtime executing node --experimental-worker with node >=10.5.0).
 *
 * @param bitLength - The required bit length for the generated prime
 * @param iterations - The number of iterations for the Miller-Rabin Probabilistic Primality Test
 *
 * @throws {@link RangeError} if bitLength < 1
 *
 * @returns A promise that resolves to a bigint probable prime of bitLength bits.
 */
export function prime(
  bitLength: number,
  iterations: number = 16,
): Promise<bigint> {
  // eslint-disable-line
  if (bitLength < 1) throw new RangeError("bitLength MUST be > 0");

  /* c8 ignore start */
  if (!_useWorkers) {
    // If there is no support for workers
    let rnd = 0n;
    do {
      rnd = fromBuffer(randBitsSync(bitLength, true));
    } while (!_isProbablyPrime(rnd, iterations));
    return new Promise((resolve) => {
      resolve(rnd);
    });
  }
  /* c8 ignore stop */
  return new Promise((resolve, reject) => {
    const workerList: Array<NodeWorker | Worker> = [];
    const _onmessage = (
      msg: WorkerToMainMsg,
      newWorker: Worker | NodeWorker,
    ): void => {
      if (msg._bcu.isPrime) {
        // if a prime number has been found, stop all the workers, and return it
        for (let j = 0; j < workerList.length; j++) {
          workerList[j].terminate(); // eslint-disable-line @typescript-eslint/no-floating-promises
        }
        while (workerList.length > 0) {
          workerList.pop();
        }
        resolve(msg._bcu.value);
      } else {
        // if a composite is found, make the worker test another random number
        const buf = randBitsSync(bitLength, true);
        const rnd = fromBuffer(buf);
        try {
          const msgToWorker: MainToWorkerMsg = {
            _bcu: {
              rnd,
              iterations,
              id: msg._bcu.id,
            },
          };
          newWorker.postMessage(msgToWorker);
        } catch (error) {
          // The worker has already terminated. There is nothing to handle here
        }
      }
    };
    if (true) {
      // browser
      const workerURL = _isProbablyPrimeWorkerUrl();
      for (let i = 0; i < self.navigator.hardwareConcurrency - 1; i++) {
        const newWorker = new Worker(workerURL);
        newWorker.onmessage = (event) => _onmessage(event.data, newWorker);
        workerList.push(newWorker);
      }
    } else {
      // Node.js
    }
    for (let i = 0; i < workerList.length; i++) {
      randBits(bitLength, true)
        .then(function (buf: Uint8Array | Buffer) {
          const rnd = fromBuffer(buf);
          workerList[i].postMessage({
            _bcu: {
              rnd,
              iterations,
              id: i,
            },
          });
        })
        .catch(reject);
    }
  });
}

/**
 * A probably-prime (Miller-Rabin), cryptographically-secure, random-number generator.
 * The sync version is NOT RECOMMENDED since it won't use workers and thus it'll be slower and may freeze thw window in browser's javascript. Please consider using prime() instead.
 *
 * @param bitLength - The required bit length for the generated prime
 * @param iterations - The number of iterations for the Miller-Rabin Probabilistic Primality Test
 *
 * @throws {@link RangeError} if bitLength < 1
 *
 * @returns A bigint probable prime of bitLength bits.
 */
export function primeSync(bitLength: number, iterations: number = 16): bigint {
  if (bitLength < 1) throw new RangeError("bitLength MUST be > 0");
  let rnd = 0n;
  do {
    rnd = fromBuffer(randBitsSync(bitLength, true));
  } while (!_isProbablyPrime(rnd, iterations));
  return rnd;
}