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XML: Encrypt element contents

First set TElXMLEncryptor.EncryptedDataType property to xedtContent.

Next, setup properties, related to encryption algorithm and keys, such as TElXMLEncryptor.EncryptionMethod, TElXMLEncryptor.KeyData and optionally TElXMLEncryptor.KeyName.

Then call TElXMLEncryptor.Encrypt() method and pass the node, whose contents you need to be encrypted.

Call Save() method of TElXMLEncryptor class. The method will return the node, which contains the encrypted data.

Finally you need to clear the content of the XML element and add the encrypted node.

C#:


void Encrypt(TElXMLDOMElement ParentElement, ByteArray AESKey)
{
  TElXMLEncryptor Encryptor = new TElXMLEncryptor(null);
  Encryptor.EncryptedDataType =  TElXMLEncryptedDataType.xedtContent;
  Encryptor.EncryptionMethod = TElXMLEncryptionMethod.xemAES;

  // setup the key
  TElXMLKeyInfoSymmetricData SymKeyData = new TElXMLKeyInfoSymmetricData(true);
  SymKeyData.Key.Key = AESKey;
  SymKeyData.Key.GenerateIV(16 * 8); // generate random IV (initialization vector)
  Encryptor.KeyData = SymKeyData;

  // encrypt the data
  Encryptor.Encrypt(ParentElement);

  TElXMLDOMElement EncryptedNode = Encryptor.Save(ParentElement.OwnerDocument);

  // then clear the content of the xml element and add the encrypted node
  while (ParentElement.LastChild != null)
    ParentElement.RemoveChild(ParentElement.LastChild);

  ParentElement.AppendChild(EncryptedNode);
}
Delphi:

procedure Encrypt(ParentElement : TElXMLDOMElement; const AESKey : ByteArray);
var
  Encryptor : TElXMLEncryptor;
  SymKeyData : TElXMLKeyInfoSymmetricData;
  EncryptedNode : TElXMLDOMElement;
begin
  Encryptor := TElXMLEncryptor.Create(nil);
  SymKeyData := TElXMLKeyInfoSymmetricData.Create(True);
  try
    Encryptor.EncryptedDataType :=  xedtContent;
    Encryptor.EncryptionMethod := xemAES;

    // setup the key
    SymKeyData.Key.Key := AESKey;
    SymKeyData.Key.GenerateIV(16 * 8); // generate random IV (initialization vector)
    Encryptor.KeyData :=  SymKeyData;

    Encryptor.Encrypt(ParentElement);

    EncryptedNode := Encryptor.Save(ParentElement.OwnerDocument);

    // then clear the content of the xml element and add the encrypted node
    while Assigned(ParentElement.LastChild) do
      ParentElement.RemoveChild(ParentElement.LastChild);

    ParentElement.AppendChild(EncryptedNode);
  finally
    FreeAndNil(Encryptor);
    FreeAndNil(SymKeyData);
  end;
end;

How To articles about XML encryption (XMLEnc)

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