bigint-mod-arith/README.hbs

# 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).

## Usage examples

With node js:
```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
```

From a browser, you can just load the module in a html page as:
```html
<script type="module">
    import * as bigintModArith from 'bigint-mod-arith-latest.browser.mod.min.js';
    // 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
</script>
```

# bigint-mod-arith JS Doc

{{>main}}

* * *