Java IO.pdf - Nguyen Dang Binh

import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
public class FileEncryptor {
public static void main(String[] args) {
if (args.length != 2) {
System.err.println("Usage: java FileEncryptor filename password");
return;
}
String filename = args[0];
String password = args[1];
if (password.length() < 8 ) {
System.err.println("Password must be at least eight characters
long");
}
try {
FileInputStream fin = new FileInputStream(args[0]);
FileOutputStream fout = new FileOutputStream(args[0] + ".des");
// Create a key.
byte[] desKeyData = password.getBytes();
DESKeySpec desKeySpec = new DESKeySpec(desKeyData);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey desKey = keyFactory.generateSecret(desKeySpec);
// Use Data Encryption Standard.
Cipher des = Cipher.getInstance("DES/CBC/PKCS5Padding");
des.init(Cipher.ENCRYPT_MODE, desKey);
// Write the initialization vector onto the output.
byte[] iv = des.getIV();
DataOutputStream dout = new DataOutputStream(fout);
dout.writeInt(iv.length);
dout.write(iv);
byte[] input = new byte[64];
while (true) {
int bytesRead = fin.read(input);
if (bytesRead == -1) break;
byte[] output = des.update(input, 0, bytesRead);
if (output != null) dout.write(output);
}
byte[] output = des.doFinal();
if (output != null) dout.write(output);
fin.close();
dout.flush();
dout.close();
}
catch (InvalidKeySpecException e) {System.err.println(e);}
catch (InvalidKeyException e) {System.err.println(e);}
Java I/O
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