Issues with decrypting XML document on remote machines.

Hi,

I have written code to encrypt an XML file containing user credentials, to then distribute the xml file with the applicationa and decrypt at run time. It all works fine on my local machine, but when I distribute the application the xml file won' decrypt. My code is:
Encrypt:

Code:

static void Main()
        {
            //load xml file into xml document
            XmlDocument xmlDoc = new XmlDocument();

            try
            {
                xmlDoc.PreserveWhitespace = true;
                xmlDoc.Load("credentials.xml");
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            //create object to specify key container
            RSACryptoServiceProvider.UseMachineKeyStore = true;
            CspParameters cspParam = new CspParameters();
            cspParam.KeyContainerName = "XML_RSA_FTP_KEY";
            //create key and store in container
            RSACryptoServiceProvider ftpkey = new RSACryptoServiceProvider(cspParam);


            //call encrypt method and clear key when finished
            try
            {
                Encrypt(xmlDoc, "usercredentials", "EncryptionElement1", ftpkey, "ftpkey");

                xmlDoc.Save("test1.xml");
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
}

 public static void Encrypt(XmlDocument Doc, string ElementToEncrypt, string EncryptionElementID, RSA Alg, string Keyname)
        {
            if (Doc == null)
                throw new ArgumentNullException("Doc");
            if (ElementToEncrypt == null)
                throw new ArgumentNullException("Element to Encrypt");
            if (EncryptionElementID == null)
                throw new ArgumentNullException("EncryptionElementID");
            if (Alg == null)
                throw new ArgumentNullException("ALG");
            //specify which xml elements to encrypt
            XmlElement elementToEncrypt = Doc.GetElementsByTagName(ElementToEncrypt)[0] as XmlElement;

            if (elementToEncrypt == null)
                throw new XmlException("The specified element was not found");
            try
            {

                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);


                DataReference dRef = new DataReference();

                dRef.Uri = "#" + EncryptionElementID;

                ek.AddReference(dRef);
                edElement.KeyInfo.AddClause(new KeyInfoEncryptedKey(ek));

                KeyInfoName kin = new KeyInfoName();

                kin.Value = Keyname;

                ek.KeyInfo.AddClause(kin);

                edElement.CipherData.CipherValue = encryptedElement;

                EncryptedXml.ReplaceElement(elementToEncrypt, edElement, false);
            }
            catch (Exception e)
            {
                throw e;
            }
        }

Any help greatly appreciated.

Thanks,

Darren.


Decrypt:

Code:

public static string Decrypt()
        {
                //create XML documentobject and load config file
                XmlDocument xmlDoc = new XmlDocument();

                try
                {
                    xmlDoc.Load("config.xml");
                }
                catch (FileNotFoundException e)
                {
                    Console.WriteLine(e.Message);
                    Console.ReadLine();

                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                    Console.ReadLine();
                }
                RSACryptoServiceProvider.UseMachineKeyStore = true;
                //create container for key
                CspParameters cspParam = new CspParameters();
                cspParam.KeyContainerName = "XML_RSA_FTP_KEY";
                //create key and store in container
                RSACryptoServiceProvider ftpkey = new RSACryptoServiceProvider(cspParam);
                //add keyname mapping qnd decrypt the document
                EncryptedXml exml = new EncryptedXml(xmlDoc);
                exml.AddKeyNameMapping("ftpkey", ftpkey);
                exml.DecryptDocument();
                
                //pass decrypted document to extract credentials method
                string details =  Extract_Credentials(xmlDoc);

                //return decrypted log in details
                return details;

        }

This like looks suspicious, especially if it works on your machine but nobody else's.

Code:

RSACryptoServiceProvider.UseMachineKeyStore = true;

--edit--
looks like the pub/private keys are being stored locally. in order to decrypt, you will need one of them to be distributed as well (careful with this).

Originally Posted by neandrake

This like looks suspicious, especially if it works on your machine but nobody else's.

Code:

RSACryptoServiceProvider.UseMachineKeyStore = true;

--edit--
looks like the pub/private keys are being stored locally. in order to decrypt, you will need one of them to be distributed as well (careful with this).

Forgive my ignorance, but which one within my code is the private key and how would I go about distributing that to the client machines?

Thanks

Actually, it looks like UseMachineKeyStore is ignored when passing CspParameters into the RSACryptoServiceProvider constructor.

Look here for your question:
RSA.ToXmlString Method (System.Security.Cryptography)