C# file Decryption - Bad Data
- by Jon
Hi all,
I am in the process of rewriting an old application. The old app stored data in a scoreboard file that was encrypted with the following code:
private const String SSecretKey = @"?B?n?Mj?";
public DataTable GetScoreboardFromFile()
{
FileInfo f = new FileInfo(scoreBoardLocation);
if (!f.Exists)
{
return setupNewScoreBoard();
}
DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
//A 64 bit key and IV is required for this provider.
//Set secret key For DES algorithm.
DES.Key = ASCIIEncoding.ASCII.GetBytes(SSecretKey);
//Set initialization vector.
DES.IV = ASCIIEncoding.ASCII.GetBytes(SSecretKey);
//Create a file stream to read the encrypted file back.
FileStream fsread = new FileStream(scoreBoardLocation, FileMode.Open, FileAccess.Read);
//Create a DES decryptor from the DES instance.
ICryptoTransform desdecrypt = DES.CreateDecryptor();
//Create crypto stream set to read and do a
//DES decryption transform on incoming bytes.
CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read);
DataTable dTable = new DataTable("scoreboard");
dTable.ReadXml(new StreamReader(cryptostreamDecr));
cryptostreamDecr.Close();
fsread.Close();
return dTable;
}
This works fine. I have copied the code into my new app so that I can create a legacy loader and convert the data into the new format. The problem is I get a "Bad Data" error:
System.Security.Cryptography.CryptographicException was unhandled
Message="Bad Data.\r\n"
Source="mscorlib"
The error fires at this line:
dTable.ReadXml(new StreamReader(cryptostreamDecr));
The encrypted file was created today on the same machine with the old code. I guess that maybe the encryption / decryption process uses the application name / file or something and therefore means I can not open it.
Does anyone have an idea as to:
A) Be able explain why this isn't working?
B) Offer a solution that would allow me to be able to open files that were created with the legacy application and be able to convert them please?
Thank you
