XML Canonicalization

Question

Hi I have to canonicalize some XML data in order to apply a particular digital signature algorithm. I read about SignedXML and XmlDsigC14NTransform classes I read the http://www.dotnet247.com/247reference/a.aspx?u=http://www.c-sharpcorner.com/Code/2002/Mar/XMLSignatureSL001.asp article too. But I can't find any way to isolate the canonicalization process from the whole process. In my problem I have to compute a signature (using a MD5) from the concatenation of a key (a customised key from none of the standard ones) and the canonical representation of a part of an XML blob of data. May someone give me some link or idea ? Thanks.

vishalmah · Answer

Hi Ram What if I just need to canonicalize a portion (and not complete) of the xml document. Can you suggest how this can be done. I tried writing code in C# like the following where the input xml is a SOAP document: XmlDocument doc = new XmlDocument(); doc.Load(soapmessage.xml); XmlNodeList list = doc.GetElementsByTagName(Body doc.DocumentElement.NamespaceURI); XmlDsigExcC14NTransform transform = new XmlDsigExcC14NTransform(); transform.LoadInput(list); Stream output = (Stream) transform.GetOutput(); StreamReader reader = new StreamReader(output); while (reader.Peek() >= 0) { Console.Write((char)reader.Read()); } The output that I observe is: This is strange because body contains a child element also! Do you know what am I missing? Thanks in advance Vishal

lsitaraman · Answer

Hello Use the Web Services Security Enhancements toolkit 1.0 or 2.0 and use the System.Security.Cryptography.Xml namespace. You can use XmlDsigC14NTransform class with the LoadInput method ( input data being your XML DOM Document Object). use the GetOutput method from the XmlDsigC14NTransform object and typecast it to memory stream. Read the data back from the memory stream and save to file. You get the Canonicalized XML. Just to really if the Canonicalization works Just put the order of attributes in XML dcoument in random manner and after Canonicallization you should see the output with attributes in alphabetical Order. Thanks Sitaraman Lakshminarayanan ( Ram)