Base64 string signature

In my project, I have a rule that I need to sign the string of an XML that I have that is in base64 with the user's CPF ...

I have been searching, but I have not been able to understand how this signature works with .NET classes.

Well, I found this link here that subscribes to a string of an XML of NF-e. But I could not quite understand how that works, and how to adapt that code to my scenario.

The codes I have are:

//Cria o xml com as tags e faz o encoding para base64
var sb = new StringBuilder();
var settings = new XmlWriterSettings();
string cpf = "000.001.000-00";

using (var writer = XmlWriter.Create(sb, settings))
{
    //Inicia o documetno xml
    writer.WriteStartDocument();

    //escreve o documento raiz
    writer.WriteStartElement("no1");

    //escreve os subelementos
    writer.WriteElementString("no2", "valor");

    //encerra o elemento raiz
    writer.WriteEndElement();

    //escreve o xml para o arquivo e encerra o objeto escritor
    writer.Close();
}

//encoding do xml para base64
string s = EncodeTo64(sb.ToString());

//arquivo que vai ser usado para gerar a string base64      
string caminho = parametros.Propriedades["ParPastaArquivoXML"].ToString();
caminho = caminho + "\" + "arquivo.xml";

File.WriteAllText(caminho, s);

Here you try to sign:

try
   {
       // Create a new CspParameters object to specify 
       // a key container.
       CspParameters cspParams = new CspParameters();
       cspParams.KeyContainerName = cpf;

       // Create a new RSA signing key and save it in the container. 
       RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider(cspParams);

       // Create a new XML document.
       XmlDocument xmlDoc = new XmlDocument();

       // Load an XML file into the XmlDocument object.
       xmlDoc.PreserveWhitespace = false;
       xmlDoc.Load(caminho);

       // Sign the XML document. 
       SignXml(xmlDoc, rsaKey);

       Console.WriteLine("XML file signed.");

       // Save the document.
       xmlDoc.Save(caminhoAssinado);
   }
   catch (Exception e)
   {
       Console.WriteLine(e.Message);
   }

Here's the method to sign:

// Sign an XML file.  
// This document cannot be verified unless the verifying  
// code has the key with which it was signed. 
public static void SignXml(XmlDocument xmlDoc, RSA Key)
{
    // Check arguments. 
    if (xmlDoc == null)
        throw new ArgumentException("xmlDoc");
    if (Key == null)
        throw new ArgumentException("Key");

    // Create a SignedXml object.
    SignedXml signedXml = new SignedXml(xmlDoc);

    // Add the key to the SignedXml document.
    signedXml.SigningKey = Key;

    // Create a reference to be signed.
    Reference reference = new Reference();
    reference.Uri = "";

    // Add an enveloped transformation to the reference.
    XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();
    reference.AddTransform(env);

    // Add the reference to the SignedXml object.
    signedXml.AddReference(reference);

    // Compute the signature.
    signedXml.ComputeSignature();

    // Get the XML representation of the signature and save 
    // it to an XmlElement object.
    XmlElement xmlDigitalSignature = signedXml.GetXml();

    // Append the element to the XML document.
    xmlDoc.DocumentElement.AppendChild(xmlDoc.ImportNode(xmlDigitalSignature, true));
}

The example XML that is created follows:

<?xml version="1.0" encoding="utf-16"?>
<no1>
  <no2>021303</no2>
</no1>

Until that time I can generate the base64 hash .

But now, how do I sign this hash with the CPF ?