README

Constant-time implementations of RFC 4648 encoding (Base64, Base32, Hex) and other variants.

This library aims to offer character encoding functions that do not leak information about what you are encoding/decoding via processor cache misses.

Features

• Constant-Time Encoding/Decoding: Prevents cache-timing attacks.
• Multiple Encodings:
  • Base64 (RFC 4648)
  • Base64UrlSafe (URL-safe variant)
  • Base64DotSlash (Crypt version, ./[A-Z][a-z][0-9])
  • Base64DotSlashOrdered (Ordered variant, [.-9][A-Z][a-z])
  • Base32 (RFC 4648)
  • Base32Hex (RFC 4648 base32hex)
  • Hex (Base16)
• Security: Uses pack() and unpack() instead of chr() and ord() for safer bit manipulation.
• Robust: Strict padding validation (optional).

Requirements

• PHP 7.4 or newer (including PHP 8.x).

Installation

composer require skywalker-labs/constant-time-encoding

Usage

You can use the Skywalker\ConstantTime\Encoding class as a facade for all encoding methods, or use specific classes directly.

Using the Encoding Facade

use Skywalker\ConstantTime\Encoding;

// Sample data
$data = random_bytes(32);

// Base64
echo Encoding::base64Encode($data), "\n";

// Base32 (Uppercase)
echo Encoding::base32EncodeUpper($data), "\n";

// Base32 (Standard)
echo Encoding::base32Encode($data), "\n";

// Hex (Base16)
echo Encoding::hexEncode($data), "\n";
echo Encoding::hexEncodeUpper($data), "\n";

Using Specific Classes

If you only need a specific encoding, you can import the relevant class directly:

use Skywalker\ConstantTime\Base64;
use Skywalker\ConstantTime\Base32;
use Skywalker\ConstantTime\Hex;

$data = random_bytes(32);

// Encode
$b64 = Base64::encode($data);
$b32 = Base32::encode($data);
$hex = Hex::encode($data);

// Decode
$raw = Base64::decode($b64);

Output Example

1VilPkeVqirlPifk5scbzcTTbMT2clp+Zkyv9VFFasE=
2VMKKPSHSWVCVZJ6E7SONRY3ZXCNG3GE6ZZFU7TGJSX7KUKFNLAQ====
2vmkkpshswvcvzj6e7sonry3zxcng3ge6zzfu7tgjsx7kukfnlaq====
d558a53e4795aa2ae53e27e4e6c71bcdc4d36cc4f6725a7e664caff551456ac1
D558A53E4795AA2AE53E27E4E6C71BDCC4D36CC4F6725A7E664CAFF551456AC1

Security

This library was designed to eliminate cache-timing side-channels from encoding operations. It is intended for use in cryptographic contexts where timing leaks could expose sensitive data.

Support

If your company uses this library in their products or services, you may be interested in purchasing a support contract from Skywalker Labs.

License

This project is licensed under the MIT License - see the LICENSE.txt file for details.