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Can anyone help me with decrypting an XML file?
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24-09-2010 12:02pm#1I am trying to to download and decrypt an encrypted XML file.
I have implemented the download part and have tested with an unencrypted file and it works fine.
However I now need to be able to download an XML file that has been encrypted using AES and the key "XXXX"
So I am only concerned with decryption as the encryption on the XML file is already done.
Here is my code so far:public NodeList getXMLDoc(){ URL url; NodeList nl = null; try{ String xmlFeed = context.getString(R.string.xml_feed); try { url = new URL(xmlFeed); URLConnection urlConnection; urlConnection = url.openConnection(); HttpURLConnection httpConnection = (HttpURLConnection) urlConnection; int responseCode = httpConnection.getResponseCode(); if(responseCode == HttpURLConnection.HTTP_OK){ String bytes = toHex("XXXX"); SecretKeySpec skeySpec = new SecretKeySpec(toByte(bytes), "AES"); try { c.init(Cipher.DECRYPT_MODE, skeySpec); //c.doFinal(); } catch (InvalidKeyException e) { e.printStackTrace(); } InputStream in = httpConnection.getInputStream(); CipherInputStream cis = new CipherInputStream(in, c); DocumentBuilderFactory dbf; dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document dom = db.parse(cis); Element docEle = dom.getDocumentElement(); nl = docEle.getElementsByTagName(TAG_CHAR); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } } finally{ } return nl; }At the minute I am trying to decrypt the whole file using CipherInputStream is this the correct approach?
My code above gives me the following exception:WARN/System.err(5274): java.io.IOException: last block incomplete in decryption
Is this a setup error or what might be causing this error?
Are there any tutorials on how to decrypt an XML file in Android/Java?
Am I going in the right direction as to how to decrypt the file or is my code completely wrong?Tagged:0
Comments
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Updated Code:
public NodeList getRoutingDoc(){ URL url; NodeList nl = null; try{ String xmlFeed = context.getString(R.string.xml_feed) + IMEI + ".xml"; try { url = new URL(xmlFeed); URLConnection urlConnection; urlConnection = url.openConnection(); HttpURLConnection httpConnection = (HttpURLConnection) urlConnection; int responseCode = httpConnection.getResponseCode(); if(responseCode == HttpURLConnection.HTTP_OK){ String bytes = toHex("XXXX"); Key skeySpec = new SecretKeySpec(toByte(bytes), "AES"); InputStream in = httpConnection.getInputStream(); System.out.println(toByte(bytes)); Cipher c = Cipher.getInstance("AES/CFB8/NoPadding"); c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes))); CipherInputStream cis = new CipherInputStream(in, c); cis.read(new byte[16]); BufferedReader br = new BufferedReader(new InputStreamReader(cis)); System.out.println("Got message"); System.out.println(br.readLine()); DocumentBuilderFactory dbf; dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document dom = db.parse(in); //cis.close(); Element docEle = dom.getDocumentElement(); nl = docEle.getElementsByTagName(TAG_CHAR); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } catch (InvalidKeyException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidAlgorithmParameterException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchAlgorithmException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchPaddingException e) { // TODO Auto-generated catch block e.printStackTrace(); } } finally{ } return nl; }
I have updated my code to the latest version I have.
I am now using the CipherInputStream properly I think and getting the file in but the System.out.println gives me the following output:INFO/System.out(7880): �=k�KV�a��_|F��(# -�Ñ.��u���n�|��~����9�<Ã*�|T��sUWlj�9�qeo�M%�t�V�V�3Q"� T�Yq?��E����H%fo���M�un��-���ȓ������<d��{���{�!�[&��%��M�.�jq+��,�b����� ��~����)��*ܨ)��>��i���b�_"��F)�`"�
So it looks as if its no decrypting it at all or not decrypting it properly??
Can anyone see what I am doing wrong?0 -
not a java head but are you trying to decrypt the file as you get stream/download it ?
if so download and save first and the decrypt it.0 -
not a java head but are you trying to decrypt the file as you get stream/download it ?
if so download and save first and the decrypt it.
Thanks, I changed it so now I download the file first.
Then run the following:Cipher c = Cipher.getInstance("AES/CFB8/NoPadding"); c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes))); CipherInputStream cis = new CipherInputStream(new FileInputStream(enc_File), c); cis.read(new byte[16]); BufferedReader br = new BufferedReader(new InputStreamReader(cis)); Log.d("XXXX", br.readLine());
But it still doesn't seem to be decoding the file, my log prints out the same sort of junk as before:�=k�KV�a��_|F��(# -�Ñ.��u���n�|��~����9�<Ã*�|T��sUWlj�9�qeo�M%�t�V�V�3Q"� T�Yq?��E����H%fo���M�un��-���ȓ������<d��{���{�!�[&��%��M�.�jq+��,�b����� ��~����)��*ܨ)��>��i���b�_"��F)�`"�0 -
Another update:
I have changed the code to test encryption first and then decryption so the code is now as follows:Cipher c = Cipher.getInstance("AES/CFB8/NoPadding"); ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(keyFile)); oos.writeObject(skeySpec); c.init(Cipher.ENCRYPT_MODE, skeySpec); CipherOutputStream cos = new CipherOutputStream(new FileOutputStream(testFile), c); PrintWriter pw = new PrintWriter(new OutputStreamWriter(cos)); pw.println("Stand and unfold yourself"); pw.close(); oos.writeObject(c.getIV()); oos.close(); c.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(toByte(bytes))); CipherInputStream cis = new CipherInputStream(new FileInputStream(testFile), c); Log.d("XXXX", br.readLine());
This log now prints out the following:DEBUG/(13642): �l�ŀ���Õ*(��� yourself
So it looks like its decoding the last part of it but not the rest?
Any ideas?0 -
How is the file being saved? Could there be an issue with how the webserver serves the file (binary rather than text)? What is apparently decrypted is sufficiently non-random enough to look like an xml file that's been improperly encoded initially. The word 'yourself' is also 8 characters. Is there a chance that you have a short read situation where only some of the input data is being read and processed? I don't know Java well enough to debug the code but look at how the initial data is encrypted (padding etc).
Regards...jmcc0 -
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