Why do i get an "IllegalBlockSizeException"?

Question

I have a piece of code which encrypts a string and stores it into a txt file. But when i come to decrypt the file i get the following error
Exception in thread "main" javax.crypto.IllegalBlockSizeException: Input length
(with padding) not multiple of 8 bytes
at com.sun.crypto.provider.DESCipher.a(DashoA6275)
at com.sun.crypto.provider.DESCipher.engineDoFinal(DashoA6275)
at com.sun.crypto.provider.DESCipher.engineDoFinal(DashoA6275)
at javax.crypto.Cipher.doFinal(DashoA6275)
at javamailerprogram.DES.decrypt(DES.java:110)
at javamailerprogram.DES.main(DES.java:120)
This is my code
package javamailerprogram;
import java.security.*;
import java.security.*;
import javax.crypto.*;
import java.io.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
import javax.crypto.spec.SecretKeySpec;
import java.util.*;
import java.security.interfaces.*;
public class DES {
static SecretKey newKey;
static String ENCRYPTION_TYPE = "DES";
static int KEY_SIZE = 56;
static SecretKeySpec skeySpec;
static SecretKeySpec spec;
static Cipher fileCipher;
public DES(){
Provider sunJce = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunJce);
try {
Security.addProvider(new com.sun.crypto.provider.SunJCE());
KeyGenerator keyGen = KeyGenerator.getInstance(ENCRYPTION_TYPE);
keyGen.init(KEY_SIZE);
ObjectInputStream in = new ObjectInputStream(new FileInputStream("c:/des.key"));
SecretKey bfSKey = (SecretKey)in.readObject();
byte[] raw = bfSKey.getEncoded();
skeySpec = new SecretKeySpec(raw, ENCRYPTION_TYPE);
} catch (Exception e) {
e.printStackTrace();
public void encrypt(String fileName, String fileNameTo) throws Exception {
byte[] encryptedText;
BufferedReader d
= new BufferedReader(new InputStreamReader(new FileInputStream(fileName)));
StringBuffer line = new StringBuffer("");
String lines = "";
while((lines = d.readLine()) !=null){
     line.append(lines);
fileCipher = Cipher.getInstance(ENCRYPTION_TYPE);
fileCipher.init(Cipher.ENCRYPT_MODE, skeySpec);
encryptedText = fileCipher.doFinal(line.toString().getBytes());
FileOutputStream out = new FileOutputStream(fileNameTo);
out.write(encryptedText);
System.out.println("Done");
public String encryptMessage(String textToEncrypt, String fileNameTo) throws Exception {
byte[] encryptedText;
fileCipher = Cipher.getInstance(ENCRYPTION_TYPE);
fileCipher.init(Cipher.ENCRYPT_MODE, skeySpec);
encryptedText = fileCipher.doFinal(textToEncrypt.getBytes());
FileOutputStream out = new FileOutputStream(fileNameTo);
out.write(encryptedText);
System.out.println("Done");
return fileNameTo;
public String encryptMessage(String textToEncrypt) throws Exception {
byte[] encryptedText;
fileCipher = Cipher.getInstance(ENCRYPTION_TYPE);
fileCipher.init(Cipher.ENCRYPT_MODE, skeySpec);
encryptedText = fileCipher.doFinal(textToEncrypt.getBytes());
System.out.println("Done");
return new String(encryptedText);
public String decrypt(String fileName) throws Exception {
byte[] decryptedText;
fileCipher = Cipher.getInstance(ENCRYPTION_TYPE);
BufferedReader d
= new BufferedReader(new InputStreamReader(new FileInputStream(fileName)));
StringBuffer line = new StringBuffer("");
String lines = "";
while((lines = d.readLine()) !=null){
     line.append(lines);
System.out.println(line.length());
byte[] theDecryptedText = line.toString().getBytes();
fileCipher.init(Cipher.DECRYPT_MODE, skeySpec);
decryptedText = fileCipher.doFinal(theDecryptedText);
return new String(decryptedText);
public static void main(String[] args) throws Exception {
new DES();
//new DES().encrypt("c:\\encr.txt", "C:\\Encr2.txt");
new DES().encryptMessage("dsgfkdsfdsfudsagifugsadfuigsalidguflasgdfulagsdgfldsagfldsu", "C:\\Encr3.txt");
System.out.println(new DES().decrypt("C:\\Encr3.txt"));
} // end main
} // end SourceViewer2

Answer 1

That's because this byte[] encryptedText;
encryptedText = fileCipher.doFinal(textToEncrypt.getBytes());
return new String(encryptedText); is illegal. You cannot create a String out of any random binary array. Take a look at the API documentation of the String(byte[]) constructor. The only byte arrays you can construct a String out of are ones that conform to a supported encoding scheme, such as ASCII, UTF-8, etc. Cipher.doFinal() returns a byte array that does not conform to any encoding scheme. If you absolutely have to turn your encrypted byte array into a String, then you will need to use Base64 encoding. There is a Base64 encoding package to be found here: http://ostermiller.org/utils/Base64.html .
HTH
- Daniel