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# Constant-Time Encoding
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[](https://github.com/paragonie/constant_time_encoding/actions)
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[](https://github.com/paragonie/constant_time_encoding/actions)
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[](https://packagist.org/packages/paragonie/constant_time_encoding)
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[](https://packagist.org/packages/paragonie/constant_time_encoding)
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[](https://packagist.org/packages/paragonie/constant_time_encoding)
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[](https://packagist.org/packages/paragonie/constant_time_encoding)
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Based on the [constant-time base64 implementation made by Steve "Sc00bz" Thomas](https://github.com/Sc00bz/ConstTimeEncoding),
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this library aims to offer character encoding functions that do not leak
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information about what you are encoding/decoding via processor cache
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misses. Further reading on [cache-timing attacks](http://blog.ircmaxell.com/2014/11/its-all-about-time.html).
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Our fork offers the following enhancements:
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* `mbstring.func_overload` resistance
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* Unit tests
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* Composer- and Packagist-ready
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* Base16 encoding
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* Base32 encoding
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* Uses `pack()` and `unpack()` instead of `chr()` and `ord()`
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## PHP Version Requirements
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Version 3 of this library should work on **PHP 8** or newer.
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Version 2 of this library should work on **PHP 7** or newer. See [the v2.x branch](https://github.com/paragonie/constant_time_encoding/tree/v2.x).
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For PHP 5 support, see [the v1.x branch](https://github.com/paragonie/constant_time_encoding/tree/v1.x).
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If you are adding this as a dependency to a project intended to work on PHP 5 through 8.4, please set the required version to `^1|^2|^3`.
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## How to Install
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```sh
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composer require paragonie/constant_time_encoding
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```
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## How to Use
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```php
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use ParagonIE\ConstantTime\Encoding;
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// possibly (if applicable):
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// require 'vendor/autoload.php';
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$data = random_bytes(32);
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echo Encoding::base64Encode($data), "\n";
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echo Encoding::base32EncodeUpper($data), "\n";
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echo Encoding::base32Encode($data), "\n";
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echo Encoding::hexEncode($data), "\n";
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echo Encoding::hexEncodeUpper($data), "\n";
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```
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Example output:
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```
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1VilPkeVqirlPifk5scbzcTTbMT2clp+Zkyv9VFFasE=
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2VMKKPSHSWVCVZJ6E7SONRY3ZXCNG3GE6ZZFU7TGJSX7KUKFNLAQ====
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2vmkkpshswvcvzj6e7sonry3zxcng3ge6zzfu7tgjsx7kukfnlaq====
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d558a53e4795aa2ae53e27e4e6c71bcdc4d36cc4f6725a7e664caff551456ac1
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D558A53E4795AA2AE53E27E4E6C71BDCC4D36CC4F6725A7E664CAFF551456AC1
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```
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If you only need a particular variant, you can just reference the
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required class like so:
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```php
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use ParagonIE\ConstantTime\Base64;
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use ParagonIE\ConstantTime\Base32;
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$data = random_bytes(32);
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echo Base64::encode($data), "\n";
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echo Base32::encode($data), "\n";
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```
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Example output:
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```
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1VilPkeVqirlPifk5scbzcTTbMT2clp+Zkyv9VFFasE=
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2vmkkpshswvcvzj6e7sonry3zxcng3ge6zzfu7tgjsx7kukfnlaq====
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```
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## Support Contracts
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If your company uses this library in their products or services, you may be
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interested in [purchasing a support contract from Paragon Initiative Enterprises](https://paragonie.com/enterprise).
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