Send and receive encrypted data between PHP and JAVA. part 1

Part1. Using a secret key to encrypt and decrypt data

In this example we use AES-128 (rijndael-128) and CBC method, so we use a secret key and an initial vector key (iv key) to encrypt and decrypt data.

Encryption in JAVA

// The keys
String secretKey = "1234567890abcde";
String ivKey = "fedcba9876543210";

// Create key specs
SecretKeySpec keySpec = new SecretKeySpec(secretKey.getBytes(), "AES");
IvParameterSpec ivSpec = new IvParameterSpec(ivKey.getBytes());

// the text that we want to encrypt
String plaintext = "this is the text that we want to encrypt in java";

// pad the string
String padded = padString16(plaintext);

// Instance the chipper
Cipher cipherEc = Cipher.getInstance("AES/CBC/NoPadding");

// init the chipper with key specs
cipherEc.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);

// Encrypt the text
byte[] encrypted = cipherEc.doFinal(padded.getBytes());

// Encode the text with base 64
BASE64Encoder encoder = new BASE64Encoder();
System.out.println(encoder.encode(encrypted));

The output of script above is:

VD9X9nF6uENC+H8TKazjztadnp6wO7kqUBvpH7tQPrWYGLaB8ltR99U2VZ/MGtIeE5yhNr2aYE3hM6Mgm+jhRg==

The pad string method

// pad string needed because the string lenght must be a multiplication of 16
private String padString16(String text) {
   int mod = 16 - (text.length() % 16);
   String empty = "";
   for (int i = 0 ; i < mod ; i++){
      empty = empty.concat(" ");
   }
   return text.concat(empty);
}

Decryption in PHP

// The keys
String secretKey = "1234567890abcde";
String ivKey = "fedcba9876543210";

$cryptedText = "VD9X9nF6uENC+H8TKazjztadnp6wO7kqUBvpH7tQPrWYGLaB8ltR99U2VZ/MGtIeE5yhNr2aYE3hM6Mgm+jhRg==";

// Decode the encrypted text
$text = base64_decode($cryptedText);

// open and init the mcrypt module
$td = mcrypt_module_open("rijndael-128", "", "cbc", $ivKey);
mcrypt_generic_init($td, $secretKey, $ivKey);

// decrypt the text
$decrypted = mdecrypt_generic($td, $text);

// deinit and close the mcrypt module
mcrypt_generic_deinit($td);
mcrypt_module_close($td);

echo $decrypted;

the output of script above is “this is the text that we want to encrypt in java”

Encryption in PHP

// The keys
String secretKey = "1234567890abcde";
String ivKey = "fedcba9876543210";

$plaintext = "this is the text that we want to encrypt in php";

// Open and init the mcrypt library with the keys
$td = mcrypt_module_open("rijndael-128", "", "cbc", $ivKey);
mcrypt_generic_init($td, $secretKey, $ivKey);

// encrypt the text
$crypt_text = mcrypt_generic($td, $plaintext);

// deinit and close mcrypt module
mcrypt_generic_deinit($td);
mcrypt_module_close($td);

// encode with base 64
echo base64_encode($crypt_text);

The output of above script is

VD9X9nF6uENC+H8TKazjztadnp6wO7kqUBvpH7tQPrU/WKCMgKV6cPwoP+75ju5u

Decryption in JAVA

// The keys
String secretKey = "1234567890abcde";
String ivKey = "fedcba9876543210";

// Create key specs
SecretKeySpec keySpec = new SecretKeySpec(secretKey.getBytes(), "AES");
IvParameterSpec ivSpec = new IvParameterSpec(ivKey.getBytes());

// Instance the chipper
Cipher cipherDc = Cipher.getInstance("AES/CBC/NoPadding");

// init the chipper with key specs
cipherDc.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

// insert the encrypted string
String message = "VD9X9nF6uENC+H8TKazjztadnp6wO7kqUBvpH7tQPrU/WKCMgKV6cPwoP+75ju5u";

// Decode the encrypted string with base 64
BASE64Decoder decoder = new BASE64Decoder();
byte[] decodedMessage = decoder.decodeBuffer(message);

byte[] outText = cipherDc.doFinal(decodedMessage);
System.out.println(new String(outText).trim());

the output of script above is “this is the text that we want to encrypt in php“