Use DataReference to encrypt and decrypt multiple XML elements using different session keys. : Encryption « Security « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Security
3. Encryption

using System;
using System.Xml;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;

class Program
{
    static void Main(string[] args)
    {
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.PreserveWhitespace = true;
        xmlDoc.Load("test.xml");
        RSA rsaKey = new RSACryptoServiceProvider();
        // Encrypt the "creditcard" element.
        Encrypt(xmlDoc, "creditcard", "EncryptedElement1", rsaKey, "rsaKey");

        // Encrypt the "creditcard2" element.
        Encrypt(xmlDoc, "creditcard2", "EncryptedElement2", rsaKey, "rsaKey");

        Console.WriteLine("Encrypted XML:");
        Console.WriteLine(xmlDoc.OuterXml);

        // Decrypt the "creditcard" element.
        Decrypt(xmlDoc, rsaKey, "rsaKey");
        
        Console.WriteLine("Decrypted XML:");
        Console.WriteLine(xmlDoc.OuterXml);
        rsaKey.Clear();
    }
    public static void Encrypt(XmlDocument Doc, string ElementToEncrypt, string EncryptionElementID, RSA Alg, string KeyName)
    {
        XmlElement elementToEncrypt = Doc.GetElementsByTagName(ElementToEncrypt)[0] as XmlElement;

        RijndaelManaged sessionKey = new RijndaelManaged();
        sessionKey.KeySize = 256;

        EncryptedXml eXml = new EncryptedXml();

        byte[] encryptedElement = eXml.EncryptData(elementToEncrypt, sessionKey, false);

        EncryptedData edElement = new EncryptedData();
        edElement.Type = EncryptedXml.XmlEncElementUrl;
        edElement.Id = EncryptionElementID;

        edElement.EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncAES256Url);

        EncryptedKey ek = new EncryptedKey();

        byte[] encryptedKey = EncryptedXml.EncryptKey(sessionKey.Key, Alg, false);

        ek.CipherData = new CipherData(encryptedKey);
        ek.EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncRSA15Url);
        edElement.KeyInfo = new KeyInfo();

        KeyInfoName kin = new KeyInfoName();
        kin.Value = KeyName;
        ek.KeyInfo.AddClause(kin);

        DataReference dRef = new DataReference();
        dRef.Uri = "#" + EncryptionElementID;

        ek.AddReference(dRef);
        edElement.KeyInfo.AddClause(new KeyInfoEncryptedKey(ek));
        edElement.CipherData.CipherValue = encryptedElement;
        EncryptedXml.ReplaceElement(elementToEncrypt, edElement, false);
    }

    public static void Decrypt(XmlDocument Doc, RSA Alg, string KeyName)
    {
        EncryptedXml exml = new EncryptedXml(Doc);
        exml.AddKeyNameMapping(KeyName, Alg);
        exml.DecryptDocument();

    }

}

//  <root>
//     <creditcard xmlns="myNamespace" Id="tag1">
//         <number>A</number>
//         <expiry>02/02/2011</expiry>
//     </creditcard>
//     <creditcard2 xmlns="myNamespace" Id="tag2">
//         <number>2</number>
//         <expiry>02/02/2012</expiry>
//     </creditcard2>
// </root>