I have generated on my android application a pair of RSA Keys.

I receive from a web service
- an AES Key, encrypted with my RSA public key 
- a String encoded with the AES key.

So I must do the following:
- decrypt the AES Key
- decrypt the string with the obtained AES Key.

To generate the RSA Keys I did:

```
 keyGen = KeyPairGenerator.getInstance("RSA");
  keyGen.initialize(size);
  keypair = keyGen.genKeyPair();
  privateKey = keypair.getPrivate();
  publicKey = keypair.getPublic();

```

On RSA decrypt I use :

```
public static byte[] decryptRSA( PrivateKey key, byte[] text) throws Exception
      { 
          byte[] dectyptedText = null;

          Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
          cipher.init(Cipher.DECRYPT_MODE, key);
          dectyptedText = cipher.doFinal(text);
          return dectyptedText;
      }

```

On AES decrypt I use:

```
public static byte[] decryptAES(byte[] key, byte[] text) throws Exception {   
            SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");   
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS1Padding");   
            cipher.init(Cipher.DECRYPT_MODE, skeySpec);   
            byte[] decrypted = cipher.doFinal(text);   
            return decrypted;   
        }

```

So, in my code, to obtain the decrypted AES Key I do

```
byte[] decryptedAESKey = sm.decryptRSA(key, Base64.decode(ReceivedBase64EncryptedAESKey));
byte[] decryptedString = sm.decryptAES(decryptedAESKey, Base64.decode(ReceivedEncryptedAESString));

```

On the end I get a null for decryptedString.
What am I doing wrong ?