Signing data

To prove that some data has come from someone we trust, it can be signed. Actually, you don't sign the data itself; instead, you sign a hash of the data. We will use the RSA algorithm combined with the SHA256 algorithm.

Signing with SHA256 and RSA

In the Ch11_CryptographyLib class library project, add the following code to the Protector class:

    public static string PublicKey; 
 
    public static string ToXmlString( 
      this RSA rsa, bool includePrivateParameters) 
    { 
      var p = rsa.ExportParameters(includePrivateParameters); 
      XElement xml; 
      if (includePrivateParameters) 
      { 
        xml = new XElement("RSAKeyValue" 
          , new XElement("Modulus", Convert.ToBase64String(p.Modulus)) 
          , new XElement("Exponent",  
            Convert.ToBase64String(p.Exponent)) 
          , new XElement("P", Convert.ToBase64String(p.P)) 
          , new XElement("Q", Convert.ToBase64String(p.Q...