Source code of the Decrypter Class
The decrypter class has a Decrypt function which accepts the encrypted file and the password to be used for the decryption process. The filename to be passed has to be a .enc file and the same password that was used for the encryption process is required to be used.
package encdecexample;
import java.awt.Color;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;
/**
*
* @author Me
*/
public class Decrypter {
public static String currentFileWithoutEncExt = "";
public static void Decrypt(File SourceFile, char[] PassWord){
//Accepts a .enc file, creates a decrypted file without extension .enc.
//As the file retains extension while crypting, the original file with original extension is obtained.
//Deletes the .enc file in the end.
FileInputStream inFile = null;
FileOutputStream FileToWrite = null;
try {
int buffer = 4096; // The buffer for read and write FileIO
String SourceFilePath = SourceFile.getPath();
String DestFilePath = SourceFilePath.substring(0, SourceFilePath.length() - 4);//strip .enc
currentFileWithoutEncExt = DestFilePath;
inFile = new FileInputStream(SourceFile);
FileToWrite = new FileOutputStream(DestFilePath);
byte[] keyData = null;;
keyData = new String(PassWord).getBytes();
SecretKeySpec secretKeySpec = new SecretKeySpec(keyData, "BlowFish");
Cipher cipher = null;
cipher = Cipher.getInstance("BlowFish");
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
byte[] input = new byte[buffer];
byte[] output = null;
int bytesRead;
while ((bytesRead = inFile.read(input)) != -1) {
output = cipher.update(input, 0, bytesRead);
if (output != null) {
FileToWrite.write(output);
}
}//end while
output = null;
output = cipher.doFinal();
if (output != null) {
FileToWrite.write(output);
}
inFile.getChannel().close();
inFile.close();
FileToWrite.getChannel().close();
FileToWrite.close();
SourceFile.delete();//delete the enc file
} catch (BadPaddingException | IllegalBlockSizeException | NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IOException ex) {
Logger.getLogger(Decrypter.class.getName()).log(Level.SEVERE, null, ex);
if (ex.toString().contains("IOException") || ex.toString().contains("FileNotFound") || ex.toString().contains("AccessDenied") || ex.toString().contains("FileAlreadyExists")) {
System.out.println("\nERROR : Failure in decrypting : " + SourceFile.getPath() + "\nError details : " + ex.toString());
// An unexpected error has happened , usually file system aaccess permissions,disk full etc
} else {
System.out.println("\nERROR : Failure in decrypting. Please check the algorithm and password.\n" + "Error while decrypting the file : " + SourceFile.getPath() + "\nError details : " + ex.toString());
}
try {
inFile.getChannel().close();
inFile.close();
FileToWrite.getChannel().close();
FileToWrite.close();
File f = new File(currentFileWithoutEncExt);
boolean success = f.delete();
if (success) {
System.out.println("\nSuccessfully deleted the partially decrypted file : " + currentFileWithoutEncExt);
} else {
System.out.println("\nERROR : Error deleting the partially decrypted file : " + currentFileWithoutEncExt);
System.out.println("\nYou must manually delete the file.");
}
return;
} catch (IOException ex1) {
Logger.getLogger(Decrypter.class.getName()).log(Level.SEVERE, null, ex);
return;
}
}
}
}
Usage
Compile and build the jar file.
Copy the jar file in a convenient folder.
Open command prompt
The syntax of the command to run is
java -jar encdec.jar <encrypt|decrypt>
for example
To Encrypt ( assuming desert.jpg and encdec.jar are in the same folder)
java -jar encdec.jar desert.jpg encrypt 12345a
encryption will create the file desert.jpg.enc
To Decrypt ( assuming desert.jpg.enc and encdec.jar are in the same folder)
java -jar encdec.jar desert.jpg.enc decrypt 12345a
decryption will again create the file desert.jpg
That is all.
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