Padding is invalid and cannot be removed [Cryptography]

[floppyzedolfin]

Hi there.

I'm coding an encryption / decryption program.
At this very moment, I think I should be pretty close from the end,
but there's something blocking me on my way.

There's a "Padding is invalid and cannot be removed" error raised when
closing the cryptostream (or FlushFinalBlock-ing it).
For what I have read, Padding errors are due to an incorrect padding :
PKCS7 is recommended.
But sadly, even using rijndaelAlg.Pad ding = Padding.PKCS7; , the error
is still raised.
Here's the code.
using System;
using System.Collecti ons.Generic,
using System.Text;
using System.IO;
using System.Security .Cryptography;
namespace Project
{
class EncryptedData
{
// contains the names of the files where encrypted
data will be
stored
public string Enc_File
{
get {return enc_file};
set {enc_file = value};
}
string enc_file;
public string Enc_Key
{
get {return enc_key};
set {enc_key = value};
}
string enc_key;
public string Enc_IV
{
get {return enc_IV};
set {enc_IV = value};
}
string enc_IV;
}
class LetsDoIt
{
const int RSA_KEY_SIZE = 4096;
static void Main()
{
try
{
RSACryptoServic eProvider RSACrypto =
new
RSACryptoServic eProvider(RSA_K EY_SIZE);
EncryptedData encFiles = new
EncryptedData() ;
encFiles = encrypt("toEncr ypt.txt",
RSACrypto.Expor tParameters(fal se));
string decFile = decrypt(encFile s,
RSACrypto.Expor tParameters(tru e));
}
catch (Exception e) { Console.WriteLi ne("Error
in Main: {0}",
e.Message); }
}
static EncryptedData encrypt(string FileToEncrypt,
RSAParameters
RSAParam)
{
try
{
// Part 1 : encrypting data
// 1 : create a Rijndael instance.
Rijndael rijndaelAlg =
Rijndael.Create ();
rijndaelAlg.Mod e = CipherMode.CBC;
/* rijndaelAlg.Pad ding = PaddingMode.PKC S7; */
rijndaelAlg.Gen erateKey();
rijndaelAlg.Gen erateIV();
ICryptoTransfor mer rijndaelEncrypt or
=
rijndael.Create Encryptor(rijnd aelAlg.Key, rijndaelAlg.IV) ;
// 2 : open source and destination
files
FileStream fstf =
File.Open(FileT oEncrypt, FileMode.OpenOr Create);

EncryptedData encryptedFiles = new
EncryptedData() ;
encryptedFiles. Enc_File =
"encryptedFile" ;
FileStream fstef = new
FileSream(encry ptedFiles.Enc_F ile,
FileMode.OpenOr Create);
// 3 : Encrypting data
CryptoStream cstf = new
CryptoStream(fs tef, rijndaelEncrypt or,
CryptoStreamMod e.Write);
byte[] bEncFile = new byte[(int)fstf.Lengt h];
fstf.Read(bEncF ile, 0, (int)bEncFile.L ength);
cstf.Write(bEnc File, 0, (int)bEncFile.L ength)
// 4 : closing streams
cstf.Close();
fstef.Close();
fstf.Close();
// Part 2 : encrypting keys
// 1 : create a RSA instance, and
import the public keys
RSACryptoServic eProvider RSA = new
RSACryptoServic eProvider(RSA_K EY_SIZE);
RSA.ImportParam eters(RSAParam) ;
// 2 : encrypt Rijndael keys
byte[] EncKey_byte =
RSA.Encrypt(rij ndaelAlg.Key, false);
byte[] EncIV_byte =
RSA.Encrypt(rij ndaelAlg.IV, false);

encryptedFiles. Enc_Key = "Enc_Key";
encryptedFiles. Enc_IV = "Enc_IV";

ByteToFile(EncK ey_byte, encryptedFiles. Enc_Key);
ByteToFile(EncI V_byte, encryptedFiles. Enc_IV);
return encryptedFiles;
}
catch (Exception e) { Console.WriteLi ne("Error
in encrypt: {0}",
e.Message); }
}
static string decrypt(Encrypt edData encData,
RSAParameters RSAParam)
{
try
{
// 1 : get files' contents
byte[] EncKey_byte =
FileToByte(encD ata.Enc_Key);
byte[] EncIV_byte = FileToByte(encD ata.Enc_IV);
// 2 : decrypt keys with RSA
algorithm
RSACryptoServic eProvider RSA =
RSACryptoServic eProvider();
RSA.ImportParam eters(RSAParam) ;
byte[] Key_byte =
RSA.Decrypt(Enc Key_byte, false);
byte[] IV_byte =
RSA.Decrypt(Enc IV_byte, false);
// 3 : decrypt the file using the
rijndael keys
Rijndael rijndaelAlg =
Rijndael.Create ();
rijndaelAlg.Mod e = CipherMode.CBC;
/* rijndaelAlg.Pad ding = PaddingMode.PKC S7; */
ICryptoTransfor m rijndaelDecrypt or =
rijndaelAlg.Cre ateDecryptor(Ke y_byte, IV_byte);
FileStream fstef =
File.Open(encDa ta.Enc_File, FileMode.Open);
string DecFile = "dec_file";
FileStream fstf = File.Open(DecFi le, FileMode.OpenOr Create);
CryptoStream cstef = new
CryptoStream(fs tef, rijndaelDecrypt or,
CryptoStreamMod e.Write);
byte[] bDecFile = new byte[(int)fstef.Leng th];
fstef.Read(bDec File, 0, (int)bDecFile.L ength];
cstef.Write(bDe cFile, 0, (int)bDecFile.L ength]

// 4 : Closing Streams
cstef.Close(); // Here's where things are bad :(
fstef.Close();
fstf.Close();

return DecFile;
}
catch (Exception e) { Console.WriteLi ne("Error
in decrypt: {0}",
e.Message); }
}

static byte[] FileToByte(stri ng FileName)
{
FileStream fst = new FileStream(File Name, FileMode.Open);
byte[] b_data = new byte[(int)fst.Length];
fst.Read(b_data , 0, (int)b_data.Len gth);
fst.Close();
return b_data;
}

static void ByteToFile(byte[] b_data, string FileName);
{
FileStream fst = new FileStream(File Name, FileMode.OpenOr Create);
fst.Write(b_dat a, 0, (int)b_data.Len gth);
fst.Close();
}
}

[rossum]

On Thu, 19 Jul 2007 03:22:34 -0700, floppyzedolfin
<fl************ @gmail.comwrote :

// 3 : decrypt the file using the rijndael keys
Rijndael rijndaelAlg = Rijndael.Create ();
rijndaelAlg.Mod e = CipherMode.CBC;
/* rijndaelAlg.Pad ding = PaddingMode.PKC S7; */

Assuming you have correctly copied your code, you could try
uncommenting this line.

ICryptoTransfor m rijndaelDecrypt or = rijndaelAlg.Cre ateDecryptor(Ke y_byte, IV_byte);

If that wasn't the problem, then try cutting down your code to a
*minimal* program that exhibits the same problem. Often this process
will show you where the problem is.

rossum

[floppyzedolfin]

On 19 juil, 12:43, rossum <rossu...@coldm ail.comwrote:

On Thu, 19 Jul 2007 03:22:34 -0700, floppyzedolfin

<floppyzedol... @gmail.comwrote :

// 3 : decrypt the file using the rijndael keys
Rijndael rijndaelAlg = Rijndael.Create ();
rijndaelAlg.Mod e = CipherMode.CBC;
/* rijndaelAlg.Pad ding = PaddingMode.PKC S7; */

Assuming you have correctly copied your code, you could try
uncommenting this line.

I've tried it before commenting it - and it was completely
unsuccessful. And it's the same for other padding modes (such as None,
Zeros, ANSIX923 or ISO10126)

There must be something I've got wrong, but I can't see what :(

[rossum]

On Fri, 20 Jul 2007 00:15:37 -0700, floppyzedolfin
<fl************ @gmail.comwrote :

>On 19 juil, 12:43, rossum <rossu...@coldm ail.comwrote:

>On Thu, 19 Jul 2007 03:22:34 -0700, floppyzedolfin

<floppyzedol.. [e-mail] e:

// 3 : decrypt the file using the rijndael keys
Rijndael rijndaelAlg = Rijndael.Create ();
rijndaelAlg.Mod e = CipherMode.CBC;
/* rijndaelAlg.Pad ding = PaddingMode.PKC S7; */

Assuming you have correctly copied your code, you could try
uncommenting this line.

I've tried it before commenting it - and it was completely
unsuccessful . And it's the same for other padding modes (such as None,
Zeros, ANSIX923 or ISO10126)

There must be something I've got wrong, but I can't see what :(

There are lots of things wrong with it, it wouldn't even compile
correctly on my machine.

public string Enc_File
{
get {return enc_file};

Your }; should be ;}

set {enc_file = value};

Ditto.

public string Enc_Key

Same again.

public string Enc_IV

And again.

byte[] bEncFile = new byte[(int)fstf.Lengt h];

Unmatched ]

cstf.Write(bEnc File, 0, (int)bEncFile.L ength)

Missing ;

byte[] bDecFile = new byte[(int)fstef.Leng th];

Unmatched ]

fstef.Read(bDec File, 0, (int)bDecFile.L ength];

Same again.

cstef.Write(bDe cFile, 0, (int)bDecFile.L ength]

And again.

static void ByteToFile(byte[] b_data, string FileName);

Do you *really* want a semicolon at the end of that line?

{
FileStream fst = new FileStream(File Name, FileMode.OpenOr Create);
fst.Write(b_dat a, 0, (int)b_data.Len gth);
fst.Close();
}

If you want us to help, then it is in your interest to post
*compilable* code. We should be able to cut and paste from your
posting into our compilers and get it to compile first time. Your
code fails this test. Compile your code and when it compiles OK cut
and paste it into your posting.

rossum