c# - Encrypt Query String including keys

Question

I have an app that is using query string to pass some values around pages. I found few examples on how to encrypt values in query string, but the problem is that my KEYS tell more about query string then the values which are all integers converted to string.

Is there a way to encrypt the whole query string in ASP.NET including keys and key values?

Something like:

Default.aspx?value1=40&value2=30&value3=20

to

 Default.aspx?56sdf78fgh90sdf4564k34klog5646l

Thanks!

Answer 1

There is one issue that many of the references above overlook, and that is just prior to returning the encrypted string, URL Encode (see below right before the string is returned). I am using IIS 7.5, and it will automatically "Decode" the string for you, so the decryption "should" be OK. Both the Encrypt and Decrypt code is shown below.

public string EncryptQueryString(string inputText, string key, string salt)
{
    byte[] plainText = Encoding.UTF8.GetBytes(inputText);

    using (RijndaelManaged rijndaelCipher = new RijndaelManaged())
    {
        PasswordDeriveBytes secretKey = new PasswordDeriveBytes(Encoding.ASCII.GetBytes(key), Encoding.ASCII.GetBytes(salt));
        using (ICryptoTransform encryptor = rijndaelCipher.CreateEncryptor(secretKey.GetBytes(32), secretKey.GetBytes(16)))
        {
            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(plainText, 0, plainText.Length);
                    cryptoStream.FlushFinalBlock();
                    string base64 = Convert.ToBase64String(memoryStream.ToArray());

                    // Generate a string that won't get screwed up when passed as a query string.
                    string urlEncoded = HttpUtility.UrlEncode(base64);
                    return urlEncoded;
                }
            }
        }
    }
}

public string DecryptQueryString(string inputText, string key, string salt)
        {
            byte[] encryptedData = Convert.FromBase64String(inputText);
            PasswordDeriveBytes secretKey = new PasswordDeriveBytes(Encoding.ASCII.GetBytes(key), Encoding.ASCII.GetBytes(salt));

            using (RijndaelManaged rijndaelCipher = new RijndaelManaged())
            {
                using (ICryptoTransform decryptor = rijndaelCipher.CreateDecryptor(secretKey.GetBytes(32), secretKey.GetBytes(16)))
                {
                    using (MemoryStream memoryStream = new MemoryStream(encryptedData))
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                        {
                            byte[] plainText = new byte[encryptedData.Length];
                            cryptoStream.Read(plainText, 0, plainText.Length);
                            string utf8 = Encoding.UTF8.GetString(plainText);
                            return utf8;
                        }
                    }
                }
            }
        }