byte[] from CryptoStream

[Mister E]

I have this method, with takes in path to a file on the system, encrypts it, and then writes the encrypted file to disk using the file path as a name and ".enc" extension. It works fine, and I am able to decrypt the file later with a different function:

public void Encrypt(string fileName)
{
FileStream fsCrypt=new FileStream(fileName + ".enc", FileMode.Create);

RijndaelManaged RMCrypto = new RijndaelManaged();

CryptoStream cs = new CryptoStream(fsCrypt,
	RMCrypto.CreateEncryptor(key,iv),   
	CryptoStreamMode.Write);

FileStream fsIn=new FileStream(fileName,FileMode.Open);

int data;
while ((data=fsIn.ReadByte())!=-1)
	cs.WriteByte((byte) data);

fsIn.Close();
cs.Close();
fsCrypt.Close();
}

Here's the problem. Instead of writing to disk, I want to get the encrypted stream directly into a byte[] array. I'm trying to do this as follows:

public byte[] Encrypt(byte[] plainFile)
{

MemoryStream cryptoStream = new MemoryStream();
Stream fsCrypt = (Stream)cryptoStream;

RijndaelManaged RMCrypto = new RijndaelManaged();

CryptoStream cs = new CryptoStream(fsCrypt,
	RMCrypto.CreateEncryptor(this.key,this.iv),   
	CryptoStreamMode.Write);

Stream fsIn = (Stream)new MemoryStream( plainFile );

int data;
while ((data=fsIn.ReadByte())!=-1)
	cs.WriteByte((byte) data);



byte[] temp = new byte[ cryptoStream.Length ];

int count = 0;
while ((data=cryptoStream.ReadByte())!=-1)
{
	temp[count++] = (byte)data;
}

fsIn.Close();
cs.Close();
fsCrypt.Close();

return temp;
}

This seems to work, but the returned byte[] does not appear to be the correct size -- even though I am using the exact same key (this.key) and initialization vector (this.iv) in both methods.

 

Unencrypted file: 327,286 bytes

Encrypted file #1: 327,296 bytes (first method)

Encrypted file #2: 327,280 bytes (second method)

 

When I try to decyrpt the #2 file, I get the following exception:

 

PKCS7 padding is invalid and cannot be removed

 

I'm obviously not doing something right in method #2. The byte[] in #2 is exactly 16 bytes smaller. I don't know if this is a conicidence, but that is the size of the Key and IV in the Rijndael class. Any help is appreciated. Thanks...

Edited August 14, 2004 by Mister E

[Joe Mamma]

did you look at this?

 

 

http://support.microsoft.com/default.aspx?scid=kb;en-us;842791

[Mister E]

Hmmm... no, I didn't. But that is interesting. It really doesn't apply to me though, as I KNOW that I'm using the same IV. Thanks anyway.

 

I found a better way to do it:

 

public byte[] Encrypt(byte[] plainFile)
{
RijndaelManaged myRijndael = new RijndaelManaged();

ICryptoTransform encryptor = myRijndael.CreateEncryptor( this.key, this.iv );
   
MemoryStream msEncrypt = new MemoryStream();

CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);

csEncrypt.Write(plainFile, 0, plainFile.Length);

csEncrypt.FlushFinalBlock();

return msEncrypt.ToArray();
}

public byte[] Decrypt(byte[] encryptedFile)
{
RijndaelManaged myRijndael = new RijndaelManaged();

ICryptoTransform decryptor = myRijndael.CreateDecryptor(this.key,this.iv);

MemoryStream msDecrypt = new MemoryStream(encryptedFile);

CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);

byte[] fromEncrypt = new byte[encryptedFile.Length];

csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);

return fromEncrypt;
}

[Khallaf]

You can check my solution to this problem and more here...

 

http://www.codeproject.com/KB/IP/2WRCS.aspx