Invalid length for a Base-64 char array during decoding/decryption

Question

Q: I face the following big problem :

from time to another i find the following exception:

Invalid length for a Base-64 char array

I use encryption and decryption:

public static string Encrypt(string text)
        {

            try
            {
                key = Encoding.UTF8.GetBytes(stringKey.Substring(0, 8));
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                Byte[] byteArray = Encoding.UTF8.GetBytes(text);
                MemoryStream memoryStream = new MemoryStream();
                CryptoStream cryptoStream = new CryptoStream(memoryStream,des.CreateEncryptor(key, IV), CryptoStreamMode.Write);
                cryptoStream.Write(byteArray, 0, byteArray.Length);
                cryptoStream.FlushFinalBlock();
                return Convert.ToBase64String(memoryStream.ToArray());
            }

            catch (Exception ex)
            {
              string message =  ex.Message;
            }

            return string.Empty;
        }



        public static string Decrypt(string text)
        {
            try
            {
                key = Encoding.UTF8.GetBytes(stringKey.Substring(0, 8));
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                text = text.Replace(" ", "+")
                Byte[] byteArray = Convert.FromBase64String(text);
                MemoryStream memoryStream = new MemoryStream();
                CryptoStream cryptoStream = new CryptoStream(memoryStream,
                des.CreateDecryptor(key, IV), CryptoStreamMode.Write);
                cryptoStream.Write(byteArray, 0, byteArray.Length);
                cryptoStream.FlushFinalBlock();
                return Encoding.UTF8.GetString(memoryStream.ToArray());
            }

            catch (Exception ex)
            {
                string message = ex.Message;

            } 

i read many articles about the problem some posts talking about the solution is:

text = text.Replace(" ", "+") and this not fixes my problem at all

my string is :3DZF/NZpp0yuQ=3D please i need help to fix this problem.

EDIT

• If there are any modifications or enhancements to this class to make it work better or more secure or avoid any possible problems like this , i will be grateful.
• If there are alternating classes instead of this,more secure and doesn't make these problems , I will be grateful.
• I use this class in a small application used to verifying mails.

---

EDIT:

Decoding the querystring values is done already when it's parsed into the Request.

https://stackoverflow.com/a/10879400/418343

Answer 1

To solve the problems you need to fist Encode and then Decode the all ready encode-base64 string, depend from where you using it.

If for example you use it on url (or query) where probably this is the place you going to use, then you need to Encode the URL before you use it, decode the url before you get it back. The reason is that you need to avoid to mix the same characters that URL use as code character, with the encrypted characters.

Anyway here is the code that solve your problem (and I use for the same reason):

public static string encodeSTROnUrl(string thisEncode)
{
    if (null == thisEncode)
        return string.Empty;

    return HttpUtility.UrlEncode(Encrypt(thisEncode));
}


public static string decodeSTROnUrl(string thisDecode)
{
    return Decrypt(HttpUtility.UrlDecode(thisDecode));
}

ps I have the same problem, and have try as you say replace the '+' and other, but at the end this is what make it works.

Don't forget to remove the text = text.Replace(" ", "+"), and other manipulations of the encryption from your code, just encrypt and decrypt.