Question

This is kind of an unusual problem. I am having difficulty encrypting a file using 3 passwords. I am attempting to wrap one CryptoStream around two other CryptoStreams, but when I write the file to the disk, it seems to become corrupted, and the padding cannot be completely removed. Why would this be happening?

Edit: Here’s some sample code

 public static Stream Encrypt(Stream source, int delcount, params keyPair[] cryptInfo)
    {

        Stream prevStream = source;
        foreach (keyPair et in cryptInfo)
        {
            Rijndael mydale = Rijndael.Create();
            mydale.BlockSize = 256;
            mydale.KeySize = 256;
            mydale.IV = et.IV;
            mydale.Key = et.key;

            CryptoStream mystream = new CryptoStream(prevStream, mydale.CreateEncryptor(), CryptoStreamMode.Write);
            prevStream = mystream;
        }
        return prevStream;

}

Here’s the full program
Program.cs

class Program
{
    static string opcode = "test";
    static string IDCID = "an ID";
    static string password = "A strong password";
    static void Main(string[] args)
    {
        if (Console.ReadLine() == "encrypt")
        {
            Stream thestream = File.Open(Environment.CurrentDirectory + "\\sample.txt", FileMode.Create, FileAccess.ReadWrite);

            PasswordDeriveBytes mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(opcode), Encoding.ASCII.GetBytes(opcode));
            byte[] key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 15).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 5 + opcode.Length * 24).ToString()));
            byte[] IV = mybytes.GetBytes(32);
            keyPair mypair = new GlobalGridCore.keyPair(IV, key);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(password), Encoding.ASCII.GetBytes(password));
            key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 9).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 7 + opcode.Length * 24).ToString()));
            IV = mybytes.GetBytes(32);
            keyPair secondpair = new keyPair(IV, key);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(IDCID), Encoding.ASCII.GetBytes(IDCID));
            key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 2).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 14 + opcode.Length * 7).ToString()));
            IV = mybytes.GetBytes(32);
            keyPair thirdpair = new keyPair(IV, key);
            keyPair[] list = new keyPair[] { mypair, secondpair, thirdpair };
            thestream = gridCrypto.Encrypt(thestream, 0, list);
            BinaryWriter mywriter = new BinaryWriter(thestream);
            mywriter.Write("ehlo");
            mywriter.Write(new byte[512]);
            mywriter.Flush();
        }
        else
        {
            Stream thestream = File.Open(Environment.CurrentDirectory + "\\sample.txt", FileMode.Open, FileAccess.ReadWrite);

            PasswordDeriveBytes mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(opcode), Encoding.ASCII.GetBytes(opcode));
            byte[] key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 15).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 5 + opcode.Length * 24).ToString()));
            byte[] IV = mybytes.GetBytes(32);
            keyPair mypair = new GlobalGridCore.keyPair(IV, key);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(password), Encoding.ASCII.GetBytes(password));
            key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 9).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 7 + opcode.Length * 24).ToString()));
            IV = mybytes.GetBytes(32);
            keyPair secondpair = new keyPair(IV, key);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes(IDCID), Encoding.ASCII.GetBytes(IDCID));
            key = mybytes.GetBytes(32);
            mybytes = new PasswordDeriveBytes(Encoding.Unicode.GetBytes((IDCID.Length + password.Length + opcode.Length * 2).ToString()), Encoding.ASCII.GetBytes((IDCID.Length + password.Length + 14 + opcode.Length * 7).ToString()));
            IV = mybytes.GetBytes(32);
            keyPair thirdpair = new keyPair(IV, key);
            keyPair[] list = new keyPair[] { mypair, secondpair, thirdpair };
            thestream = gridCrypto.Decrypt(thestream, list);
          BinaryReader myreader = new BinaryReader(thestream);
          Console.WriteLine(myreader.ReadString());
          Console.ReadLine();
        }

    }
}

cryptDriver.cs

abstract class gridCrypto
{
    /// <summary>
    /// Decrypts the input stream to the output stream
    /// </summary>
    /// <param name="source">I</param>
    /// <param name="dest">O</param>
    /// <param name="cryptInfo">U</param>
    public static Stream Decrypt(Stream source, params keyPair[] cryptInfo)
    {
        Stream prevStream = source;
        foreach (keyPair et in cryptInfo)
        {
            Rijndael mydale = Rijndael.Create();
            mydale.BlockSize = 256;
            mydale.KeySize = 256;
            mydale.IV = et.IV;
            mydale.Key = et.key;
            CryptoStream mystream = new CryptoStream(prevStream, mydale.CreateDecryptor(), CryptoStreamMode.Read);
            prevStream = mystream;
        }
        return prevStream;
    }
   /// <summary>
   /// Encrypts the input stream and securely deletes the input file with the specified number of passes. The source stream MUST have length
   /// </summary>
   /// <param name="source">The source stream (to be deleted)</param>
   /// <param name="dest">The destination stream</param>
   /// <param name="delcount">The number of passes to erase the file</param>
   /// <param name="cryptInfo">Crypto stuff</param>
    public static Stream Encrypt(Stream source, int delcount, params keyPair[] cryptInfo)
    {

        Stream prevStream = source;
        foreach (keyPair et in cryptInfo)
        {
            Rijndael mydale = Rijndael.Create();
            mydale.BlockSize = 256;
            mydale.KeySize = 256;
            mydale.IV = et.IV;
            mydale.Key = et.key;

            CryptoStream mystream = new CryptoStream(prevStream, mydale.CreateEncryptor(), CryptoStreamMode.Write);
            prevStream = mystream;
        }
        return prevStream;
        //int cpos = 0;
        //while (cpos < delcount)
        //{
        //    source.Position = 0;
        //    while (source.Position < source.Length)
        //    {
        //        if (source.Length - source.Position > 512)
        //        {
        //            Random mrand = new Random();

        //            byte[] thearray = new byte[512];
        //            mrand.NextBytes(thearray);
        //            source.Write(thearray, 0, thearray.Length);
        //        }
        //        else
        //        {
        //            Random mrand = new Random();

        //            byte[] thearray = new byte[source.Length-source.Position];
        //            mrand.NextBytes(thearray);
        //            source.Write(thearray, 0, thearray.Length);
        //            source.Flush();
        //        }
        //    }
        //    cpos += 1;
        //}
    }
}
class keyPair
{
    public byte[] IV;
    public byte[] key;
    public keyPair(byte[] InitializationVector, byte[] Key)
    {
        IV = InitializationVector;
        key = Key;
    }
}

The code to delete the file is commented out and is not used in the program.

Answer 1

It was a filesystem problem on the server. It was fixed after the server admin ran an FSRepair on the server (it happened to be a corrupt virtual hard disk, not a bug in the program).