Hash value does not match when decode a string

Question

i have the following piece of code. It has been working in my Staging and pre-production environments as well as in production.

How it has suddenly stopped working ONLY in the Production environment. It still works in pre-production and production.

It is throwing the "Hash value does not match" error meaning the storedHash != calcHash.

Any ideas why this might be happening in only of the 3 environments?

static public string StrDec(string value, string key)
{
    String dataValue = "";
    String calcHash = "";
    String storedHash = "";

    MACTripleDES mac3des = new MACTripleDES();
    MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
    mac3des.Key = md5.ComputeHash(Encoding.UTF8.GetBytes(key));
    try
    {
       string strRemoveSpace = value.Replace(" ", "+");
       dataValue = Encoding.UTF8.GetString(System.Convert.FromBase64String(strRemoveSpace.Split(System.Convert.ToChar("-"))[0]));
       storedHash = Encoding.UTF8.GetString(System.Convert.FromBase64String(strRemoveSpace.Split(System.Convert.ToChar("-"))[1]));
       calcHash = Encoding.UTF8.GetString(mac3des.ComputeHash(Encoding.UTF8.GetBytes(dataValue)));

        if (storedHash != calcHash)
        {
            //Throw exception because data was corrupted here
            throw new ArgumentException("Hash value does not match");
        }
    }
    catch (System.Exception ex)
    {
        //Catch System.Exception  here
    }
    return dataValue;
}

Answer 1

This is the problem - or at least a problem:

Encoding.UTF8.GetString(mac3des.ComputeHash(Encoding.UTF8.GetBytes(dataValue)));

... and quite possibly the same for the previous lines.

You're calling Encoding.UTF8.GetString with arbitrary binary data which isn't a UTF-8-encoded string. You mustn't do that - it's like trying to load an arbitrary blob of data as an image file.

If you want to convert some arbitrary binary data to a string, use Convert.ToBase64String or convert it to hex.