title: SagePay AES form integration
body: <p>I have a working Form Integration but need to move to v 3.00 of Form Integration which requires AES coding rather than Xor. The sample code is a J2EE app which hides away the method of encrypting. SagePay support have been unable to provide an API class/method for encrypting/decrypting; I suspect they are there, if anyone has used them and can advise on this?</p>
  
  <p>Alternatively I am trying to do the encryption in my own code. Again SagePay have not been forthcoming, in that they don't provide enough information about how the encryption is done. I believe I have worked out that the password they provide is used both for the encryption key and iv, though they don't state this in the integration guide. Here is code I have tried for encoding inString</p>
  
  <pre><code>        byte[] byteDataToEncrypt = inString.getBytes();
          final byte[] keyBytes = webSite.encryptionPassword().getBytes("ASCII");
          final byte[] ivBytes = webSite.encryptionPassword().getBytes("ASCII");
          final SecretKey key = new SecretKeySpec(keyBytes, "AES");
          final IvParameterSpec iv = new IvParameterSpec(ivBytes);
          final Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
  
          cipher.init(Cipher.ENCRYPT_MODE, key, iv);
          byte[] byteCipherText = cipher.doFinal(byteDataToEncrypt);
          byte[] aesEncryptedBase64encoded = Base64.encodeBase64(byteCipherText);
              String crypt = "@" + new String(aesEncryptedBase64encoded);
  </code></pre>
  
  <p>I do not know why @ would need to be on the front, but I have seen it in other code that has been posted online for SagePay integration. Without it SagePay test server tells me the encryption method is not recognised. With it, it tells me the Currency field is missing, though I know the currency field is set ok to "GBP" in the source and I am using the provided test server password.</p>
  
  <p>Any help very much appreciated whether from SagePay or from the developer community.
  John</p>