Cryptographic Streaming

[Dmitry Nogin]

Hi,

What is wrong about the following simple encoding/decoding code snippet pair?
I have a CryptographicException ("Padding is invalid and cannot be removed.") at the very end.



class Program

{

static void Main(string[] args)

{

byte[] cipherText = Encript("Test message", "qwerty");

string plainText = Decript(cipherText, "qwerty");

}



private static byte[] Encript(string plainText, string password)

{

byte[] salt = Encoding.ASCII.GetBytes("This is my salt");

Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(password, salt);



RijndaelManaged rm = new RijndaelManaged();

rm.IV = rfc2898.GetBytes(rm.BlockSize / 8);

rm.Key = rfc2898.GetBytes(rm.KeySize / 8);



using (MemoryStream ms = new MemoryStream())

using (ICryptoTransform ct = rm.CreateEncryptor())

using (CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write))

using (StreamWriter sw = new StreamWriter(cs))

{

sw.Write(plainText);

sw.Flush();

cs.FlushFinalBlock();

return ms.GetBuffer();

}

}



private static string Decript(byte[] cipherText, string password)

{

byte[] salt = Encoding.ASCII.GetBytes("This is my salt");

Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(password, salt);



RijndaelManaged rm = new RijndaelManaged();

rm.IV = rfc2898.GetBytes(rm.BlockSize / 8);

rm.Key = rfc2898.GetBytes(rm.KeySize / 8);



using (MemoryStream ms = new MemoryStream(cipherText))

using (ICryptoTransform ct = rm.CreateDecryptor())

using (CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Read))

using(StreamReader sr = new StreamReader(cs))

{

return sr.ReadToEnd(); // <- Exception

}

}

}



Thanks a lot,
-- dmitry

 

[Dmitry Nogin]

Sorry, it was very easy:

return ms.GetBuffer(); => return ms.ToArray();
Hi,

What is wrong about the following simple encoding/decoding code snippet pair?
I have a CryptographicException ("Padding is invalid and cannot be removed.") at the very end.



class Program

{

static void Main(string[] args)

{

byte[] cipherText = Encript("Test message", "qwerty");

string plainText = Decript(cipherText, "qwerty");

}



private static byte[] Encript(string plainText, string password)

{

byte[] salt = Encoding.ASCII.GetBytes("This is my salt");

Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(password, salt);



RijndaelManaged rm = new RijndaelManaged();

rm.IV = rfc2898.GetBytes(rm.BlockSize / 8);

rm.Key = rfc2898.GetBytes(rm.KeySize / 8);



using (MemoryStream ms = new MemoryStream())

using (ICryptoTransform ct = rm.CreateEncryptor())

using (CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write))

using (StreamWriter sw = new StreamWriter(cs))

{

sw.Write(plainText);

sw.Flush();

cs.FlushFinalBlock();

return ms.GetBuffer();

}

}



private static string Decript(byte[] cipherText, string password)

{

byte[] salt = Encoding.ASCII.GetBytes("This is my salt");

Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(password, salt);



RijndaelManaged rm = new RijndaelManaged();

rm.IV = rfc2898.GetBytes(rm.BlockSize / 8);

rm.Key = rfc2898.GetBytes(rm.KeySize / 8);



using (MemoryStream ms = new MemoryStream(cipherText))

using (ICryptoTransform ct = rm.CreateDecryptor())

using (CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Read))

using(StreamReader sr = new StreamReader(cs))

{

return sr.ReadToEnd(); // <- Exception

}

}

}



Thanks a lot,
-- dmitry