encrypt/decrypt with Android and PHP - php

Question

Sorry for this question. I've read all the previous questions, but my code still not work.
Thanks in advance to anyone that will help me in understanding where is the problem.
In android I use this code for reading the public key and produce the encrypted text:
public static PublicKey getPublicKeyFromString(String stringKey) throws Exception {
byte[] keyBytes = stringKey.getBytes();
byte[] decode = Base64.decode(keyBytes, Base64.DEFAULT);
KeyFactory fact = KeyFactory.getInstance("RSA");
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(decode);
return (PublicKey) fact.generatePublic(x509KeySpec);
}
public static String RSAEncrypt(final String plain, final PublicKey publicKey)
throws NoSuchAlgorithmException, NoSuchPaddingException,
InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
byte[] encryptedBytes;
Cipher cipher;
cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
encryptedBytes = cipher.doFinal(plain.getBytes());
return Base64.encodeToString(encryptedBytes, Base64.DEFAULT);
}
//I call these functions in this manner.
private final String pubKeyString =
//"-----BEGIN PUBLIC KEY-----" +
"MIG..." +
"...";
//"-----END PUBLIC KEY-----"
PublicKey pubKey = RSAFunctions.getPublicKeyFromString(pubKeyString);
String encData = RSAFunctions.RSAEncrypt("prova", pubKey);
The publickey.php and privatekey.php file are generated in php with this code:
<?php
include('./Crypt/RSA.php');
$rsa = new Crypt_RSA();
extract($rsa->createKey()); // == $rsa->createKey(1024) where 1024 is the key size
$File1 = "./privatekey.php";
$Handle = fopen($File1, 'w');
fwrite($Handle, "<?php \$privatekey=\"" . $privatekey . "\"?>");
fclose($Handle);
$File2 = "./publickey.php";
$Handle = fopen($File2, 'w');
fwrite($Handle, "<?php \$publickey=\"" . $publickey . "\"?>");
fclose($Handle);
?>
In php I use this code for decrypt data:
<?php
include('Crypt/RSA.php');
require('privatekey.php');
$rsa = new Crypt_RSA();
$rsa->loadKey($privatekey); // private key
$base64_string = $_GET["data"];
$base64_string = str_replace(' ', '+', $base64_string);
$ciphertext = base64_decode( $base64_string );
//$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_OAEP);
$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
$plaintext = $rsa->decrypt($ciphertext);
echo $plaintext;
?>
I've also made a php crypt script for testing my decrypt php function. This is the code of my encrypt.php:
<?php
include('Crypt/RSA.php');
require('publickey.php');
$rsa = new Crypt_RSA();
$rsa->loadKey($publickey); // public key
$plaintext = $_GET["data"];
//$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_OAEP);
$ciphertext = $rsa->encrypt($plaintext);
echo base64_encode( $ciphertext );
?>
I've no problem when encrypt and decrypt text using only php, but if I use the encrypted data made with android app, php give me an error in decrypting.
Thanks for the attention.

Answer 1

In your php there is :
CRYPT_RSA_ENCRYPTION_PKCS1
but when you create your Cipher object on Android you omit the mode and padding
cipher = Cipher.getInstance("RSA");
you should try something like
Cipher c = Cipher.getInstance("AES/CBC/PKCS1Padding");
ref :
http://developer.android.com/reference/javax/crypto/Cipher.html