# bigint-mod-arith 

Some extra functions to work with modular arithmetics using native JS (stage 3) implementation of BigInt. It can be used with Node.js (>=10.4.0) and [Web Browsers supporting BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#Browser_compatibility).

If you are looking for a cryptographically secure random generator and for probale primes (generation and testing), you may be interested in [bigint-secrets](https://github.com/juanelas/bigint-secrets)

_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 [webcrypto](https://w3c.github.io/webcrypto/Overview.html) or [node crypto](https://nodejs.org/dist/latest/docs/api/crypto.html).

## Installation
bigint-mod-arith is distributed as both an ES6 and a CJS module.

The ES6 module is built for any [web browser supporting BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#Browser_compatibility). The module only uses native javascript implementations and no polyfills had been applied.

The CJS module is built as a standard node module.

bigint-mod-arith can be imported to your project with `npm`:
```bash
npm install bigint-mod-arith
```

For web browsers, you can also [download the bundle from GitHub](https://raw.githubusercontent.com/juanelas/bigint-mod-arith/master/dist/bigint-mod-arith-latest.browser.mod.min.js) or just hotlink to it:
```html
<script type="module" src="https://raw.githubusercontent.com/juanelas/bigint-mod-arith/master/dist/bigint-mod-arith-latest.browser.mod.min.js"></script>
```

## Usage examples

```javascript
const bigintModArith = require('bigint-mod-arith');

// Stage 3 BigInts with value 666 can be declared as BigInt('666') 
// or the shorter no-linter-friendly new syntax 666n

let a = BigInt('5'); 
let b = BigInt('2'); 
let n = BigInt('19');
 
console.log(bigintModArith.modPow(a, b, n)); // prints 6
 
console.log(bigintModArith.modInv(BigInt('2'), BigInt('5'))); // prints 3
 
console.log(bigintModArith.modInv(BigInt('3'), BigInt('5'))); // prints 2
```

# bigint-mod-arith JS Doc

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