encryption.md

Encryption

• Introduction
• Configuration
  • Gracefully Rotating Encryption Keys
• Using the Encrypter

Introduction

Laravel's encryption services provide a simple, convenient interface for encrypting and decrypting text via OpenSSL using AES-256 and AES-128 encryption. All of Laravel's encrypted values are signed using a message authentication code (MAC) so that their underlying value cannot be modified or tampered with once encrypted.

Configuration

Before using Laravel's encrypter, you must set the key configuration option in your config/app.php configuration file. This configuration value is driven by the APP_KEY environment variable. You should use the php artisan key:generate command to generate this variable's value since the key:generate command will use PHP's secure random bytes generator to build a cryptographically secure key for your application. Typically, the value of the APP_KEY environment variable will be generated for you during Laravel's installation.

Gracefully Rotating Encryption Keys

If you change your application's encryption key, all authenticated user sessions will be logged out of your application. This is because every cookie, including session cookies, are encrypted by Laravel. In addition, it will no longer be possible to decrypt any data that was encrypted with your previous encryption key.

To mitigate this issue, Laravel allows you to list your previous encryption keys in your application's APP_PREVIOUS_KEYS environment variable. This variable may contain a comma-delimited list of all of your previous encryption keys:

APP_KEY="base64:J63qRTDLub5NuZvP+kb8YIorGS6qFYHKVo6u7179stY="
APP_PREVIOUS_KEYS="base64:2nLsGFGzyoae2ax3EF2Lyq/hH6QghBGLIq5uL+Gp8/w="

When you set this environment variable, Laravel will always use the "current" encryption key when encrypting values. However, when decrypting values, Laravel will first try the current key, and if decryption fails using the current key, Laravel will try all previous keys until one of the keys is able to decrypt the value.

This approach to graceful decryption allows users to keep using your application uninterrupted even if your encryption key is rotated.

Using the Encrypter

Encrypting a Value

You may encrypt a value using the encryptString method provided by the Crypt facade. All encrypted values are encrypted using OpenSSL and the AES-256-CBC cipher. Furthermore, all encrypted values are signed with a message authentication code (MAC). The integrated message authentication code will prevent the decryption of any values that have been tampered with by malicious users:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Crypt;

class DigitalOceanTokenController extends Controller
{
    /**
     * Store a DigitalOcean API token for the user.
     */
    public function store(Request $request): RedirectResponse
    {
        $request->user()->fill([
            'token' => Crypt::encryptString($request->token),
        ])->save();

        return redirect('/secrets');
    }
}

Decrypting a Value

You may decrypt values using the decryptString method provided by the Crypt facade. If the value cannot be properly decrypted, such as when the message authentication code is invalid, an Illuminate\Contracts\Encryption\DecryptException will be thrown:

use Illuminate\Contracts\Encryption\DecryptException;
use Illuminate\Support\Facades\Crypt;

try {
    $decrypted = Crypt::decryptString($encryptedValue);
} catch (DecryptException $e) {
    // ...
}