How Can I Encrypt and Decrypt Files Using OpenSSL in PHP?

Encrypting and Decrypting Files with MCrypt

The Mcrypt library provides functions for encryption and decryption operations in PHP. Here's an example of how to use it for encrypting and decrypting files:

// ENCRYPT FILE
function encryptFile() {
    $key = generateKey(); // Function to generate a secure encryption key
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-128-cbc')); // Generate a random initialization vector

    $plaintext = file_get_contents(PATH . '/ftpd/' . $file);
    $encrypted = openssl_encrypt($plaintext, 'aes-128-cbc', $key, OPENSSL_RAW_DATA, $iv);

    $encryptedFile = fopen(PATH . '/encrypted/' . $file . '.txt', 'w');
    fwrite($encryptedFile, $iv . $encrypted);
    fclose($encryptedFile);

    unlink(PATH . '/ftpd/' . $file);
}

// DECRYPT FILE
function decryptFile() {
    $key = generateKey(); // Function to generate the same encryption key used in encryption

    if ($handle = opendir(PATH . '/encrypted')) {
        while (false !== ($file = readdir($handle))) {
            if ($file != "." && $file != "..") {
                $encryptedFile = fopen(PATH . '/encrypted/' . $file, 'r');
                $encryptedData = fread($encryptedFile, filesize(PATH . '/encrypted/' . $file));

                $iv = substr($encryptedData, 0, openssl_cipher_iv_length('aes-128-cbc'));
                $decrypted = openssl_decrypt(substr($encryptedData, openssl_cipher_iv_length('aes-128-cbc')), 'aes-128-cbc', $key, OPENSSL_RAW_DATA, $iv);

                $decryptedFile = fopen(PATH . '/decrypted/' . $file, 'w');
                fwrite($decryptedFile, $decrypted);
                fclose($decryptedFile);

                // unlink(PATH . '/encrypted/' . $file);
            }
        }
        closedir($handle);
    }
}

Important notes:

• MCrypt is an outdated library and is no longer recommended for use. Consider using newer and more secure alternatives, such as OpenSSL or Libsodium.
• The encryption/decryption key must be securely generated and kept confidential.
• Initialization vectors (IVs) provide additional security by making the ciphertext unique each time for the same plaintext and key.

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