c# - Simple string encryption in .NET and Javascript

Question

I'm developing an ASP.NET MVC application in which I want to encrypt a short string on the server, using C#, and send it to the client-side.

Then on the client-side it will be decrypted through Javascript code.

Any thoughts on how to implement this?

Do you know of a simple encryption algorithm (doesn't have to be bullet-proof secure) that can be easily translated from C# to Javascript or vice-versa?

NOTE: I could do this entirely in C# and do the decryption through Ajax, but I'd prefer not to do it this way, as I want to reduce website traffic as much as possible.

Answer 1

It sounds like you want an obfuscation or encoding, not encryption. Base64 encoding should work well here. The result will look nothing like an email address, and the encoding process is fast.

In C#, you can use:

string emailAddress = "[email protected]";
string encoded = Convert.ToBase64String(Encoding.UTF8.GetBytes(emailAddress));

And you can use this JavaScript function to decode it:

function Base64Decode(encoded) {
   var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
   var output = "";
   var chr1, chr2, chr3;
   var enc1, enc2, enc3, enc4;
   var i = 0;

   do {
      enc1 = keyStr.indexOf(encoded.charAt(i++));
      enc2 = keyStr.indexOf(encoded.charAt(i++));
      enc3 = keyStr.indexOf(encoded.charAt(i++));
      enc4 = keyStr.indexOf(encoded.charAt(i++));

      chr1 = (enc1 << 2) | (enc2 >> 4);
      chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
      chr3 = ((enc3 & 3) << 6) | enc4;

      output = output + String.fromCharCode(chr1);

      if (enc3 != 64) {
         output = output + String.fromCharCode(chr2);
      }
      if (enc4 != 64) {
         output = output + String.fromCharCode(chr3);
      }
   } while (i < encoded.length);

   return output;
}

The C# application encodes the string [email protected] into YWJjQGV4YW1wbGUuY29t, and the JavaScript version will decode YWJjQGV4YW1wbGUuY29t back into [email protected].