php-aes-gcm

aes-gcm.php

<?php
    class AESGCMUtil {
        const AES_KEY_SIZE = 256; // Key size for AES
        const GCM_IV_LENGTH = 12; // IV length for GCM
        const GCM_TAG_LENGTH = 16; // Authentication tag length for GCM
    
        /**
         * Prevent instantiation of the class.
         */
        private function __construct()
        {
        }
    
        /**
         * Generate a random nonce (IV).
         *
         * @return string Hexadecimal representation of the IV
         */
        public static function getRandomNonce()
        {
            $ivBytes = random_bytes(self::GCM_IV_LENGTH);
            return bin2hex($ivBytes);
        }
    
        /**
         * Generate a secret encryption key.
         *
         * @return string Hexadecimal representation of the AES key
         */
        public static function getSecretEncryptionKey()
        {
            $key = openssl_random_pseudo_bytes(self::AES_KEY_SIZE / 8);
            return bin2hex($key);
        }
    
        /**
         * Encrypt a plaintext string.
         *
         * @param string $plainText The plaintext message to encrypt
         * @param string $secKey Hexadecimal string of the secret key
         * @param string $ivData Hexadecimal string of the IV
         * @return string Hexadecimal encrypted text
         */
        public static function encrypt($plainText, $secKey, $ivData)
        {
            $key = hex2bin($secKey);
            $iv = hex2bin($ivData);
            $cipherText = openssl_encrypt($plainText, 'aes-256-gcm', $key, OPENSSL_RAW_DATA, $iv, $tag, '', self::GCM_TAG_LENGTH);
            $cipherHex = bin2hex($cipherText . $tag); // Concatenate cipher text and tag for storage
            return $cipherHex;
        }
    
        /**
         * Decrypt an encrypted string.
         *
         * @param string $encHexString Hexadecimal string of the encrypted text and tag
         * @param string $secKey Hexadecimal string of the secret key
         * @param string $ivData Hexadecimal string of the IV
         * @return string Decrypted text
         */
        public static function decrypt($encHexString, $secKey, $ivData)
        {
            $key = hex2bin($secKey);
            $iv = hex2bin($ivData);
            $encTextWithTag = hex2bin($encHexString);
            $cipherText = substr($encTextWithTag, 0, -self::GCM_TAG_LENGTH);
            $tag = substr($encTextWithTag, -self::GCM_TAG_LENGTH);
    
            $decryptedText = openssl_decrypt($cipherText, 'aes-256-gcm', $key, OPENSSL_RAW_DATA, $iv, $tag);
            return $decryptedText;
        }
    }
    
    // Example Usage:
    $nonce = AESGCMUtil::getRandomNonce();
    $key = AESGCMUtil::getSecretEncryptionKey();
    
    echo "Nounce/IV: " . $nonce . "\n";
    echo "AES Key: " . $key . "\n";
    
    $encrypted = AESGCMUtil::encrypt("satyendra", $key, $nonce);
    $decrypted = AESGCMUtil::decrypt($encrypted, $key, $nonce);
    
    echo "Encrypted: " . strtoupper($encrypted) ."\n";
    echo "Decrypted: " . $decrypted . "\n";
?>