PHP Crypt

Secure-by-default encryption with AES-256-GCM and key rotation.

Requirements

• PHP 8.2+
• ext-openssl

Installation

composer require philiprehberger/php-crypt

Usage

Basic Encryption

use PhilipRehberger\Crypt\Crypt;

$key = Crypt::generateKey();

$encrypted = Crypt::encrypt('sensitive data', $key);
$decrypted = Crypt::decrypt($encrypted, $key);

Additional Authenticated Data (AAD)

Bind ciphertext to a context so it cannot be used elsewhere:

$encrypted = Crypt::encrypt('data', $key, aad: 'user:42');
$decrypted = Crypt::decrypt($encrypted, $key, aad: 'user:42');

Key Rotation

Re-encrypt data when rotating keys:

$rotated = Crypt::rotate($encrypted, $oldKey, $newKey);

Array Encryption

Encrypt and decrypt arrays (serialized as JSON):

$encrypted = Crypt::encryptArray(['name' => 'Alice', 'role' => 'admin'], $key);
$data = Crypt::decryptArray($encrypted, $key);

JSON Encryption

Encrypt and decrypt any JSON-serializable value:

$data = [
    'user' => ['name' => 'Alice', 'email' => 'alice@example.com'],
    'roles' => ['admin', 'editor'],
];

$encrypted = Crypt::encryptJson($data, $key);
$decrypted = Crypt::decryptJson($encrypted, $key); // returns the original structure

Key Validation

Check the strength of an encryption key:

$result = Crypt::validateKeyStrength($key);
// ['valid' => true, 'bits' => 256, 'recommendation' => null]

$weak = Crypt::validateKeyStrength(base64_encode('short'));
// ['valid' => false, 'bits' => 40, 'recommendation' => 'Key is 40-bit. A minimum of ...']

KeyChain (Multi-Key Management)

Manage key rotation transparently — encrypts with the current key, decrypts with any known key:

use PhilipRehberger\Crypt\KeyChain;

$chain = new KeyChain($newKey, $oldKey1, $oldKey2);

$encrypted = $chain->encrypt('data');
$decrypted = $chain->decrypt($encryptedWithAnyKey);

// Re-encrypt all ciphertexts with the current key
$rotated = $chain->rotateAll($ciphertexts);

API

Crypt (Static)

Method	Description
generateKey(): string	Generate a random base64-encoded 32-byte key
encrypt(string $data, string $key, ?string $aad = null): string	Encrypt data with AES-256-GCM
decrypt(string $encrypted, string $key, ?string $aad = null): string	Decrypt AES-256-GCM ciphertext
rotate(string $encrypted, string $oldKey, string $newKey): string	Re-encrypt data with a new key
encryptArray(array $data, string $key): string	Encrypt an array as JSON
decryptArray(string $encrypted, string $key): array	Decrypt a JSON-encoded array
encryptJson(mixed $data, string $key): string	JSON-encode any value then encrypt
decryptJson(string $encrypted, string $key): mixed	Decrypt then JSON-decode
validateKeyStrength(string $key): array	Check key bit length and strength

KeyChain

Method	Description
__construct(string $currentKey, string ...$previousKeys)	Create a key chain
encrypt(string $data): string	Encrypt with the current key
decrypt(string $encrypted): string	Decrypt with any key in the chain
rotateAll(array $ciphertexts): array	Re-encrypt all ciphertexts with the current key

Exceptions

Exception	When
InvalidKeyException	Key is not a valid base64-encoded 32-byte string
DecryptionException	Decryption fails (wrong key, tampered data, invalid ciphertext)

Development

composer install
vendor/bin/phpunit
vendor/bin/pint --test
vendor/bin/phpstan analyse

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License

MIT