Java Security

Hello,

We had used the following code to decrypt,

public static Document decryptXMLDocument(Document document, Key key,
			X509Certificate x509Certificate) throws DocumentEncryptException {

		try {
			if (null == document) {
				Debug.print("Document is null");
			}
			

			XMLSignatureUtil.sign((PrivateKey) key, x509Certificate, document1);
			String namespaceURI = EncryptionConstants.EncryptionSpecNS;
			String localName = EncryptionConstants._TAG_ENCRYPTEDDATA;
			Element encryptedDataElement = (Element) document
					.getElementsByTagNameNS(namespaceURI, localName).item(0);
			
			XMLCipher xmlCipher = XMLCipher.getInstance();
			if (null == xmlCipher) {
				Debug.print("xmlCipher is null");
			}

			xmlCipher.init(XMLCipher.DECRYPT_MODE, null);
			if (null == key) {
				Debug.print("key is null");
			}

			xmlCipher.setKEK(key);

			document = xmlCipher.doFinal(document, encryptedDataElement);
			Debug.print("xmlCipher.setKEK(key);" + xmlCipher.getEncryptedKey());
			return document;
		} catch (Exception e) {
			throw new DocumentEncryptException(
					"Invalid Key used for decryption");
		}
	}

This code is working for all of the documents until now. Suddenly for some documents, it is returning the same encrypted document. It is not even raising any exception.

Note: Document is almost 1 mb in size.

It is encrypted using the following code,

public static Document encryptXMLDocument(Document document, Key key)
			throws DocumentEncryptException {

		try {
			Key symmetricKey = generateDataEncryptionKey();

			XMLCipher keyCipher = null;

			keyCipher = XMLCipher.getInstance(XMLCipher.RSA_v1dot5);

			keyCipher.init(XMLCipher.WRAP_MODE, key);
			EncryptedKey encryptedKey = keyCipher.encryptKey(document,
					symmetricKey);

			Element rootElement = document.getDocumentElement();

			XMLCipher xmlCipher = XMLCipher.getInstance(XMLCipher.AES_128);
			xmlCipher.init(XMLCipher.ENCRYPT_MODE, symmetricKey);

			// Setting keyinfo inside the encrypted data being prepared.
			EncryptedData encryptedDataElement = xmlCipher.getEncryptedData();
			KeyInfo keyInfo = new KeyInfo(document);
			keyInfo.add(encryptedKey);
			encryptedDataElement.setKeyInfo(keyInfo);

			document = xmlCipher.doFinal(document, rootElement, true);
		} catch (NoSuchAlgorithmException nsae) {
			throw new DocumentEncryptException("Invalid Algorithm : "
					+ nsae.getMessage());
		} catch (XMLEncryptionException xmlee) {
			xmlee.printStackTrace();
			throw new DocumentEncryptException(
					"Document could not be Encrypted : " + xmlee.getMessage());
		} catch (Exception e) {
			e.printStackTrace();
			throw new DocumentEncryptException(
					"Document could not be Encrypted : " + e.getMessage());
		}
		return document;
	}

Could any one shed some light on this?

Thanks in advance.