Encryption Between PHP & Java

Question

I was looking to encrypt data between a PHP server and a Java Client. Individually the code works fine and I would like to stick with OpenSSL on the PHP server.

Do

Answer 1

A working version can be found - https://github.com/chaudhuri-ab/CrossPlatformCiphers

Some things to keep in mind is the that if you do not specify OPENSSL_RAW_DATA in PHP the data will be encrypted as base64. That was throwing me off.

PHP:

class PHP_AES_Cipher {

    private static $OPENSSL_CIPHER_NAME = "aes-128-cbc"; //Name of OpenSSL Cipher 
    private static $CIPHER_KEY_LEN = 16; //128 bits

    /**
     * Encrypt data using AES Cipher (CBC) with 128 bit key
     * 
     * @param type $key - key to use should be 16 bytes long (128 bits)
     * @param type $iv - initialization vector
     * @param type $data - data to encrypt
     * @return encrypted data in base64 encoding with iv attached at end after a :
     */

    static function encrypt($key, $iv, $data) {
        if (strlen($key) < PHP_AES_Cipher::$CIPHER_KEY_LEN) {
            $key = str_pad("$key", PHP_AES_Cipher::$CIPHER_KEY_LEN, "0"); //0 pad to len 16
        } else if (strlen($key) > PHP_AES_Cipher::$CIPHER_KEY_LEN) {
            $key = substr($str, 0, PHP_AES_Cipher::$CIPHER_KEY_LEN); //truncate to 16 bytes
        }

        $encodedEncryptedData = base64_encode(openssl_encrypt($data, PHP_AES_Cipher::$OPENSSL_CIPHER_NAME, $key, OPENSSL_RAW_DATA, $iv));
        $encodedIV = base64_encode($iv);
        $encryptedPayload = $encodedEncryptedData.":".$encodedIV;

        return $encryptedPayload;

    }

    /**
     * Decrypt data using AES Cipher (CBC) with 128 bit key
     * 
     * @param type $key - key to use should be 16 bytes long (128 bits)
     * @param type $data - data to be decrypted in base64 encoding with iv attached at the end after a :
     * @return decrypted data
     */
    static function decrypt($key, $data) {
        if (strlen($key) < PHP_AES_Cipher::$CIPHER_KEY_LEN) {
            $key = str_pad("$key", PHP_AES_Cipher::$CIPHER_KEY_LEN, "0"); //0 pad to len 16
        } else if (strlen($key) > PHP_AES_Cipher::$CIPHER_KEY_LEN) {
            $key = substr($str, 0, PHP_AES_Cipher::$CIPHER_KEY_LEN); //truncate to 16 bytes
        }

        $parts = explode(':', $data); //Separate Encrypted data from iv.
        $decryptedData = openssl_decrypt(base64_decode($parts[0]), PHP_AES_Cipher::$OPENSSL_CIPHER_NAME, $key, OPENSSL_RAW_DATA, base64_decode($parts[1]));

        return $decryptedData;
    }

}

Java:

package ciphers;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import java.util.Base64;

public class Java_AES_Cipher {

    private static String CIPHER_NAME = "AES/CBC/PKCS5PADDING";
    private static int CIPHER_KEY_LEN = 16; //128 bits

    /**
     * Encrypt data using AES Cipher (CBC) with 128 bit key
     * 
     * 
     * @param key  - key to use should be 16 bytes long (128 bits)
     * @param iv - initialization vector
     * @param data - data to encrypt
     * @return encryptedData data in base64 encoding with iv attached at end after a :
     */
    public static String encrypt(String key, String iv, String data) {
        try {
            if (key.length() < Java_AES_Cipher.CIPHER_KEY_LEN) {
                int numPad = Java_AES_Cipher.CIPHER_KEY_LEN - key.length();

                for(int i = 0; i < numPad; i++){
                    key += "0"; //0 pad to len 16 bytes
                }

            } else if (key.length() > Java_AES_Cipher.CIPHER_KEY_LEN) {
                key = key.substring(0, CIPHER_KEY_LEN); //truncate to 16 bytes
            }


            IvParameterSpec initVector = new IvParameterSpec(iv.getBytes("UTF-8"));
            SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");

            Cipher cipher = Cipher.getInstance(Java_AES_Cipher.CIPHER_NAME);
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, initVector);

            byte[] encryptedData = cipher.doFinal((data.getBytes()));

            String base64_EncryptedData = Base64.getEncoder().encodeToString(encryptedData);
            String base64_IV = Base64.getEncoder().encodeToString(iv.getBytes("UTF-8"));

            return base64_EncryptedData + ":" + base64_IV;

        } catch (Exception ex) {
            ex.printStackTrace();
        }

        return null;
    }

    /**
     * Decrypt data using AES Cipher (CBC) with 128 bit key
     * 
     * @param key - key to use should be 16 bytes long (128 bits)
     * @param data - encrypted data with iv at the end separate by :
     * @return decrypted data string
     */

    public static String decrypt(String key, String data) {
        try {

            String[] parts = data.split(":");

            IvParameterSpec iv = new IvParameterSpec(Base64.getDecoder().decode(parts[1]));
            SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");

            Cipher cipher = Cipher.getInstance(Java_AES_Cipher.CIPHER_NAME);
            cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);

            byte[] decodedEncryptedData = Base64.getDecoder().decode(parts[0]);

            byte[] original = cipher.doFinal(decodedEncryptedData);

            return new String(original);
        } catch (Exception ex) {
            ex.printStackTrace();
        }

        return null;
    }

}