Need help creating an exception for wrong password in decrypt method

[liftthis]

The following code works but I am trying to prevent decrypting a file if you have the wrong key.


// Example code showing how to use Java's Password-Based encryption. This
// example is a simplified form of the code in the documentation for the
// java cryptography architecture.
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.GeneralSecurityException;
//import java.security.NoSuchAlgorithmException;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
//import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.imageio.ImageIO;
import javax.crypto.spec.DESKeySpec;


public class sample
{

static String key = "squirrel123";
static String key1 = "squirrel1234";

public static void main(String[] arg) throws Exception
{


encryptFile(key, "c:\\users\\test\\rose.jpg",
"c:\\users\\test\\encrypt.jpg","JPG");

decryptFile(key1, "c:\\users\\test\\encrypt.jpg",
"c:\\users\\test\\decrypted_output.jpg","JPG");


}



public static void encryptFile(String key, String nonEncryptedFile, String EncryptedFile, String typeFile) throws GeneralSecurityException, FileNotFoundException
{


DESKeySpec dks = new DESKeySpec(key.getBytes());
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
Cipher pbeCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");


if((typeFile.equals("JPG"))||
(typeFile.equals("GIF"))||
(typeFile.equals("PNG"))||
(typeFile.equals("BMP")))
{

File inputFile = new File(nonEncryptedFile);

BufferedImage input = null;

pbeCipher.init(Cipher.ENCRYPT_MODE, desKey);

try
{
input = ImageIO.read(inputFile);
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}

FileOutputStream output = null;

try
{
output = new FileOutputStream(EncryptedFile);
}
catch
(FileNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}

CipherOutputStream cos = new CipherOutputStream(output, pbeCipher);

try
{
ImageIO.write(input,typeFile,cos);
}
catch (IOException e1)
{
// TODO Auto-generated catch block
e1.printStackTrace();
}

try
{
cos.close();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}



}


public static void doCopy(InputStream is, OutputStream os) throws IOException
{
byte[] bytes = new byte[64];
int numBytes;
while ((numBytes = is.read(bytes)) != -1) {
os.write(bytes, 0, numBytes);
}
os.flush();
os.close();
is.close();
}

public static void decryptFile(String key, String encryptedFile, String decryptedFile, String typeFile)throws GeneralSecurityException, FileNotFoundException
{

DESKeySpec dks = new DESKeySpec(key1.getBytes());
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
Cipher pbeCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");

try
{
pbeCipher.init(Cipher.DECRYPT_MODE, desKey);

System.out.println("Decrypt mode!");

// Decrypt the ciphertext and then print it out.
FileInputStream output = null;

if((typeFile.equals("JPG"))||
(typeFile.equals("GIF"))||
(typeFile.equals("PNG"))||
(typeFile.equals("BMP")))
{

try {
output = new FileInputStream(encryptedFile);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

CipherInputStream cis = new CipherInputStream(output, pbeCipher);
BufferedImage input = null;
try {
input = ImageIO.read(cis);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
FileOutputStream out = null;
try {
out = new FileOutputStream(decryptedFile);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
ImageIO.write(input,typeFile, out);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
cis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}


} catch (IOException e ){
System.out.println("invalid");
}

}

}

[keang]

Please use code tags when posting code.

The following code works but I am trying to prevent decrypting a file if you have the wrong key

What does your code do now if you enter the wrong key - how can it decrypt the file if the Key is incorrect?