Encryption in Android is equivalent to php MCRYPT_RIJNDAEL_256
I am using the following php code for encryption:
$enc_request = base64_encode(
mcrypt_encrypt(MCRYPT_RIJNDAEL_256,
$this->_app_key,
json_encode($request_params),
MCRYPT_MODE_ECB)
);
Now let's try to encrypt in android and get different encrypted string. Below is the android code:
public void enc(){
byte[] rawKey = getRawKey("my_key".getBytes());
SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal("my_message".getBytes());
String result=Base64.encodeToString(encrypted, Base64.DEFAULT);
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(256, sr);
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
Can anyone help me where I am going wrong? And get also correct encrypted string in android too.
source to share
I created a method main
in Java using Bouncy Castle to show the inner workings mcrypt_encrypt()
used in your example code.
This is basically to show other developers that PHP mcrypt_encrypt()
is a very dangerous technique to use. It won't fail a lot, but that's because it rather continues where it should have stopped long ago. For example, it adds or removes values from a key. It will throw a warning when it does, but it won't show up directly in the code.
public static void main(String[] args) throws DataLengthException, IllegalStateException, InvalidCipherTextException {
// just some constants
boolean ENCRYPT = true;
boolean DECRYPT = false;
// the key is either in binary in PHP or a string (dynamic isn't it?), lets assume ASCII
byte[] givenKey = args[0].getBytes(Charset.forName("ASCII"));
// determine the key size dynamically, somebody thought this was a good idea...
// NOTE: PHP will emit a warning if the key size is larger, but will simply use the
// largest key size otherwise
final int keysize;
if (givenKey.length <= 128 / Byte.SIZE) {
keysize = 128;
} else if (givenKey.length <= 192 / Byte.SIZE) {
keysize = 192;
} else {
keysize = 256;
}
// create a 256 bit key by adding zero bytes to the decoded key
byte[] keyData = new byte[keysize / Byte.SIZE];
System.arraycopy(givenKey, 0, keyData, 0, Math.min(givenKey.length, keyData.length));
KeyParameter key = new KeyParameter(keyData);
// create a Rijndael cipher with 256 bit block size, this is not AES
BlockCipher rijndael = new RijndaelEngine(256);
// use a padding method that only works on data that cannot end with zero valued bytes
ZeroBytePadding c = new ZeroBytePadding();
// use ECB mode encryption, which should never be used
PaddedBufferedBlockCipher pbbc = new PaddedBufferedBlockCipher(rijndael, c);
// initialize the cipher using the key (no need for an IV, this is ECB)
pbbc.init(ENCRYPT, key);
// create a plain text byte array
byte[] plaintext = args[1].getBytes(Charset.forName("UTF8"));
// create a buffer for the ciphertext
byte[] ciphertext = new byte[pbbc.getOutputSize(plaintext.length)];
int offset = 0;
offset += pbbc.processBytes(plaintext, 0, plaintext.length, ciphertext, offset);
offset += pbbc.doFinal(ciphertext, offset);
// show the ciphertext
System.out.println(new String(Hex.encode(ciphertext), Charset.forName("ASCII")));
// reverse the encryption
pbbc.init(DECRYPT, key);
byte[] decrypted = new byte[pbbc.getOutputSize(ciphertext.length)];
offset = 0;
offset += pbbc.processBytes(ciphertext, 0, ciphertext.length, decrypted, offset);
offset += pbbc.doFinal(decrypted, offset);
// this will probably print out correctly, but it isn't actually correct
System.out.println(new String(decrypted, Charset.forName("UTF8")));
// check out the zero at the end
System.out.println(new String(Hex.encode(decrypted), Charset.forName("UTF8")));
// so lets make it a bit shorter... the PHP way
// note that in PHP, the string may *not* contain a null terminator
// add it yourself before printing the string
System.out.println(new String(decrypted, Charset.forName("UTF8")).replaceAll("\\x00+$", ""));
}
Warning : the above code contains ZeroBytePadding
. Later I discovered that there is a difference between Bouncy Castle and PHP in this regard: Bouncy Castle expects you to always have to pipe, while PHP does not. Therefore Bouncy adds 1..n bytes, while PHP adds 0 .. (n-1) bytes, where n is the block size (32 bytes for Rijndael-256/256). Thus, you may have to do registration / disassembly yourself; be sure to check edge cases!
source to share