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schangxiang@126.com

2025-09-19 18966e02fb573c7e2bb0c6426ed792b38b910940

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# Timing safe string compare using double HMAC
 
[![Node.js Version](https://img.shields.io/node/v/tsscmp.svg?style=flat-square)](https://nodejs.org/en/download)
[![npm](https://img.shields.io/npm/v/tsscmp.svg?style=flat-square)](https://npmjs.org/package/tsscmp)
[![NPM Downloads](https://img.shields.io/npm/dm/tsscmp.svg?style=flat-square)](https://npmjs.org/package/tsscmp)
[![Build Status](https://img.shields.io/travis/suryagh/tsscmp/master.svg?style=flat-square)](https://travis-ci.org/suryagh/tsscmp)
[![Build Status](https://img.shields.io/appveyor/ci/suryagh/tsscmp/master.svg?style=flat-square&label=windows)](https://ci.appveyor.com/project/suryagh/tsscmp)
[![Dependency Status](http://img.shields.io/david/suryagh/tsscmp.svg?style=flat-square)](https://david-dm.org/suryagh/tsscmp)
[![npm-license](http://img.shields.io/npm/l/tsscmp.svg?style=flat-square)](LICENSE)
 
 
Prevents [timing attacks](http://codahale.com/a-lesson-in-timing-attacks/) using Brad Hill's
[Double HMAC pattern](https://www.nccgroup.trust/us/about-us/newsroom-and-events/blog/2011/february/double-hmac-verification/)
to perform secure string comparison. Double HMAC avoids the timing atacks by blinding the
timing channel using random time per attempt comparison against iterative brute force attacks.
 
 
## Install
 
```
npm install tsscmp
```
## Why
To compare secret values like **authentication tokens**, **passwords** or
**capability urls** so that timing information is not
leaked to the attacker.
 
## Example
 
```js
var timingSafeCompare = require('tsscmp');
 
var sessionToken = '127e6fbfe24a750e72930c';
var givenToken = '127e6fbfe24a750e72930c';
 
if (timingSafeCompare(sessionToken, givenToken)) {
  console.log('good token');
} else {
  console.log('bad token');
}
```
##License: 
[MIT](LICENSE)
 
**Credits to:**  [@jsha](https://github.com/jsha) |
[@bnoordhuis](https://github.com/bnoordhuis) |
[@suryagh](https://github.com/suryagh) |