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How to Securely Encrypt and Decrypt PHP Strings Using Libsodium or defuse/php-encryption?
How to Securely Encrypt and Decrypt PHP Strings Using Libsodium or defuse/php-encryption?
Dec 18, 2024 am 12:26 AM
Encrypting and Decrypting PHP Strings
Question:
How can we encrypt and decrypt a PHP string, requiring both an original string and a salt or key for both processes?
Answer:
It's crucial to understand the difference between encryption and authentication before proceeding. For robust security, we recommend encrypted authentication, which entails encrypting and then authenticating.
Avoid creating your own cryptography; instead, utilize a dependable library developed by cryptography specialists. We strongly advise using libsodium or defuse/php-encryption due to their ease of use and built-in authenticated encryption.
Encryption Steps:
- Employ AES in CTR mode for encryption.
- Authenticate the ciphertext using HMAC-SHA-256 (or Poly1305).
Decryption Steps:
- Recalculate the MAC of the ciphertext and compare it with the original MAC. Abort if there's a mismatch.
- Proceed with decryption.
Design Considerations:
- Avoid compressing ciphertext.
- Employ mb_strlen() and mb_substr() with the '8bit' character set mode.
- Utilize a CSPRNG to generate IVs. Avoid MCRYPT_RAND.
- Always encrypt before authenticating (unless using AEAD).
- Be mindful of cache timing vulnerabilities.
When Not to Use Encryption:
- Password storage (use password-hashing algorithms like Argon2 instead)
- URL parameter encryption (inappropriate tool)
Libsodium PHP Example:
function safeEncrypt(string $message, string $key): string
{
if (mb_strlen($key, '8bit') !== SODIUM_CRYPTO_SECRETBOX_KEYBYTES) {
throw new RangeException('Key is not the correct size (must be 32 bytes).');
}
$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
$cipher = base64_encode(
$nonce.
sodium_crypto_secretbox(
$message,
$nonce,
$key
)
);
return $cipher;
}
Libsodium Decryption:
function safeDecrypt(string $encrypted, string $key): string
{
$decoded = base64_decode($encrypted);
$nonce = mb_substr($decoded, 0, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, '8bit');
$ciphertext = mb_substr($decoded, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, null, '8bit');
$plain = sodium_crypto_secretbox_open(
$ciphertext,
$nonce,
$key
);
return $plain;
}
defuse/php-encryption Example:
use Defuse\Crypto\Crypto; use Defuse\Crypto\Key; $message = 'We are all living in a yellow submarine'; $key = Key::createNewRandomKey(); $ciphertext = Crypto::encrypt($message, $key); $plaintext = Crypto::decrypt($ciphertext, $key);
The above is the detailed content of How to Securely Encrypt and Decrypt PHP Strings Using Libsodium or defuse/php-encryption?. For more information, please follow other related articles on the PHP Chinese website!
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