Encrypt data passed in View Model - asp.net-mvc

Question

I have a simple post method in a MVC controller that checks whether the ModelState is valid then calls another method passing an instance of the model as a paramter. This model contains sensitive data that is easily obtained by looking at Fiddler. My goal is to somehow mask or encrypt this data so that it cannot be seen in an http trace.
I have seen posts suggesting to use Session or Temp variables but that is not an option in my case.
This is what the code looks like:
[HttpPost]
[ActionName("Search")]
[AccessControl(Xri)]
public ActionResult SearchPost(string string1, ViewModel model)
{
model.NoResults = false;
if (ModelState.IsValid)
{
if (ModelState.IsValid) return RedirectToAction("TargetAction", model);
}
}
[AccessControl(Xri)]
public ActionResult TargetAction(string arg, ViewModel viewModel)
{
.
.
.
}
Fiddler shows the following:
/TargetAction?id=01010101&date=08%2F14%2F2013%2000%3A00%3A00&To=08%2F21%2F2013%2000%3A00%3A00&param1=somevalue&param2=somevalue2
Is there a way to mask the url parameters shown here?

Answer 1

You're going to need to get SSL running on your server.
Without a server certificate from a trusted authority, there is very little you can do to encrypt the data over the wire. Why? Because you'd need to send encryption/decryption details in clear text before you start sending the data so that your client (likely JavaScript) could decode it.
Using a certificate and operating on 443 gives you built-in functionality from the server/browser that is hard to beat in a custom implementation.
If you just want to obscure the data (and put it beyond the level of most web users) you could always base64 encode the data, rather than encrypting it. Just be clear that you are NOT encrypting data and it is still possible to decode it. This approach is not a form of encryption.
If you decide to take that approach regardless, here are a few resources:
Client-side Encoding/Decoding
MSDN Reference on Encoding to Base64
Cheers.

Answer 2

You have two options for doing this:
Store the data on the server and give the user a token (e.g. a GUID) to pass along to retrieve the data. Since using the Session or TempData is not an option, you could store the viewmodel in the database, and then redirect the user with the token in the URL to retrieve it on the next request.
The other option would be to have the user pass the viewmodel in the URL as you're currently doing, but pass it in an encrypted format. For example, you could
serialize the model to JSON, encrypt it using one of .NET's built in encryption algorithms, and then redirect to the next action passing the encrypted string as your view model. Then you could change the target action to something like:
[AccessControl(Xri)]
public ActionResult TargetAction(string arg, string encryptedViewModel)
{
var decryptedString = Decrypt(encryptedViewModel) ; // supply the decrypt function to match your encryption
var viewModel = JsonConvert.DeserializeObject(decryptedString);
}