byte[] from CryptoStream

M

Mister E

Centurion
Joined
Jul 23, 2004
Messages
136
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:
Code: 
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:
Code: 
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...
 
Last edited:
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:

Code: 
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;
}
 
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