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# bigint-crypto-utils
Utils for working with cryptography using native JS ([ES-2020](https://tc39.es/ecma262/#sec-bigint-objects)) implementation of BigInt. It includes some extra functions to work with modular arithmetics along with secure random numbers and a fast strong probable prime generator/tester (parallelised multi-threaded Miller-Rabin primality test). It can be used by any [Web Browser or webview supporting BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#Browser_compatibility) and with Node.js (>=10.4.0). In the latter case, for multi-threaded primality tests, you should use Node.js v11 or newer or enable at runtime with `node --experimental-worker` with Node.js version >= 10.5.0 and < 11.
> The operations supported on BigInts are not constant time. BigInt can be therefore **[unsuitable for use in cryptography](https://www.chosenplaintext.ca/articles/beginners-guide-constant-time-cryptography.html).** Many platforms provide native support for cryptography, such as [Web Cryptography API](https://w3c.github.io/webcrypto/) or [Node.js Crypto](https://nodejs.org/dist/latest/docs/api/crypto.html).
## Installation
bigint-crypto-utils is distributed for [web browsers and/or webviews supporting BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#Browser_compatibility) as an ES6 module or an IIFE file; and for Node.js (>=10.4.0), as a CJS module.
bigint-crypto-utils can be imported to your project with `npm`:
```bash
npm install bigint-crypto-utils
```
NPM installation defaults to the ES6 module for browsers and the CJS one for Node.js.
For web browsers, you can also directly download the [IIFE file](https://raw.githubusercontent.com/juanelas/bigint-crypto-utils/master/dist/bigint-crypto-utils-latest.browser.js) or the [ES6 module](https://raw.githubusercontent.com/juanelas/bigint-crypto-utils/master/dist/bigint-crypto-utils-latest.browser.mod.min.js) from GitHub.
## Usage examples
### Node.js:
```javascript
const bigintCryptoUtils = require("bigint-crypto-utils");
/* Stage 3 BigInts with value 666 can be declared as BigInt('666')
or the shorter new no-so-linter-friendly syntax 666n.
Notice that you can also pass a number, e.g. BigInt(666), but it is not
recommended since values over 2**53 - 1 won't be safe but no warning will
be raised.
*/
let a = BigInt("5");
let b = BigInt("2");
let n = BigInt("19");
console.log(bigintCryptoUtils.modPow(a, b, n)); // prints 6
console.log(bigintCryptoUtils.modInv(BigInt("2"), BigInt("5"))); // prints 3
console.log(bigintCryptoUtils.modInv(BigInt("3"), BigInt("5"))); // prints 2
// Generation of a probable prime of 2048 bits
const prime = await bigintCryptoUtils.prime(2048);
// Testing if a prime is a probable prime (Miller-Rabin)
if (await bigintCryptoUtils.isProbablyPrime(prime))
// code if is prime
// Get a cryptographically secure random number between 1 and 2**256 bits.
const rnd = bigintCryptoUtils.randBetween(BigInt(2) ** BigInt(256));
```
### Javascript native from a browser
You can just load the module in a html page as:
```html
<script type="module">
import * as bigintCryptoUtils from "bigint-utils-latest.browser.mod.min.js";
let a = BigInt("5");
let b = BigInt("2");
let n = BigInt("19");
console.log(bigintCryptoUtils.modPow(a, b, n)); // prints 6
console.log(bigintCryptoUtils.modInv(BigInt("2"), BigInt("5"))); // prints 3
console.log(bigintCryptoUtils.modInv(BigInt("3"), BigInt("5"))); // prints 2
(async function() {
// Generation of a probable prime of 2018 bits
const p = await bigintCryptoUtils.prime(2048);
// Testing if a prime is a probable prime (Miller-Rabin)
const isPrime = await bigintCryptoUtils.isProbablyPrime(p);
alert(p.toString() + "\nIs prime?\n" + isPrime);
// Get a cryptographically secure random number between 1 and 2**256 bits.
const rnd = bigintCryptoUtils.randBetween(BigInt(2) ** BigInt(256));
alert(rnd);
})();
</script>
```
### TypeScript
BigInt is [ES-2020](https://tc39.es/ecma262/#sec-bigint-objects). In order to use it with TypeScript you should set `lib` (and probably also `target` and `module`) to `esnext` in `tsconfig.json`.
# bigint-crypto-utils JS Doc
{{>main}}
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