Cryptography Problem (BadPaddingException)

Hello there,

I´ve got a prblem to encrypt and decrypt a String.
I always get a BadPaddingException.

Where is the failure I probably made?

Thanks for your help.

Code:

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public class KryptTest2 {
 
    byte[] salt = {
              (byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
              (byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
              };
    int count=20;
 
 
//....main and some stuff
 
// Schlüssel erzeugen (create key from password)
    private SecretKey makeKeyFromPassword(String passwort) {
       
        PBEKeySpec pbeKeySpec = new PBEKeySpec(passwort.toCharArray());
        try{
            SecretKeyFactory keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
            SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
            return pbeKey;
        }
        catch(NoSuchAlgorithmException e){
            return null;}
        catch(InvalidKeySpecException e1){
            return null;
                    }
    }
 
    // Verschluesselung und Entschluesselung (encrypt and decrypt)
    private String verschlüsseln(String nachricht, SecretKey secretKey) {
        try{
            PBEParameterSpec pbeParamSpec= new PBEParameterSpec(salt, count);
            Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
            pbeCipher.init(Cipher.ENCRYPT_MODE, secretKey, pbeParamSpec);
            byte[] ciphertext= pbeCipher.doFinal(nachricht.getBytes());
            return new String(ciphertext); 
        }
        catch (Exception e){
            return null;
        }
           
    }
    private String entschlüsseln(String nachricht, SecretKey secretKey) {
        try{
            PBEParameterSpec pbeParamSpec= new PBEParameterSpec(salt, count);
            Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
            pbeCipher.init(Cipher.DECRYPT_MODE, secretKey, pbeParamSpec);
            byte[] ciphertext= pbeCipher.doFinal(nachricht.getBytes());
          return new String(ciphertext);
    }
    catch (Exception e){
        return null;
        }
    }

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Well you have to dig into security API if you don't want to change your code
but if you can do it i can recommend using sample code from this link :

Source Code File Structure

and maybe you need this:

http://sce.uhcl.edu/yang/teaching/pr...leExample.java

hope that will help

cheers

Make sure your key is 24 characters long.

Thank you FON and .
I will take a closer look at my code.

Quote:

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Make sure your key is 24 characters long.

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I will try this next.

Sorry, but this does not work properly.
I think it has somesthing with the input string to do.

If I put one more character to the input string I have a not correct decrypted message, if I remove it, I get a BadPaddingException.

I show you what I mean:
Look at the white-space between the full stop sign (.) and the word "Hallo" .
1. Two white-space
2. One white-spaces
3. zero white-spaces

1.

Quote:

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message: Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein. Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.

encrypted: ËkâÂÎÝu«ý»S[ýO¨U¡`e³¹‘ŒzÞIñI`D:Õ¤Íûš=q¥´+ÙW‘Òàdž´îb©Þ *ž¬:!|OœàÐÌ’›Pè`iÈ1*Y?wߙԸªÈÁ‡°µRkAJ¯?f¼Æì‘ÕY* *>m§q8rý5,5sµ°TdÞH1!yÅ@ŽãCjMbö´rÝi

decrypted: Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein. Hallo,êÕ¾HÈsi
eine TÊstnachriËY4Êvn? s’Nachricht darf auch länger sein.

---

But:
2.

Quote:

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message: Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein. Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.

-->
javax.crypto.BadPaddingException: Given final block not properly padded

---

3.

Quote:

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message: Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.

encrpted: ËkâÂÎÝu«ý»S[ýO¨U¡`e³¹‘ŒzÞIñI`D:Õ¤Íûš=q¥´+ÙW‘Òàdž´îb©Þ *ž¬
:!|®küz–j”íß(Ü'OdZ!dØ|Êî±Ìbµ8…j¶ãô±
}¾ùZºk¹Z Ê
(Ö04Ž#8§™è\Âç©·¦qåƼoÇán5ë"Šÿ,÷

decrypted: Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.

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I guess my problem remains to the input string.

I think I have to use pbeCipher.update() and then pbeCipher.doFinal().
But I don't know how to use the update function properly. I haven't found any example how to use it.

Good evening,

just for completion. A member of the German Java-Forum found a solution.

Thx for your help.

Code:

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import java.io.UnsupportedEncodingException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

import org.marre.sms.SmsPduUtil;
 
public class Encrypt {
 
    final String PBEWithMD5AndDES = "PBEWithMD5AndDES";
    final int iterations = 8;
    final byte[] salt = {
        (byte) 0xc7, (byte) 0x73, (byte) 0x21, (byte) 0x8c,
        (byte) 0x7e, (byte) 0xc8, (byte) 0xee, (byte) 0x99
    };
 
    public SecretKey makeKeyFromPassword(String passwort) throws NoSuchAlgorithmException, InvalidKeySpecException {
 
        final KeySpec pbeKeySpec = new PBEKeySpec(passwort.toCharArray());
        return SecretKeyFactory.getInstance(PBEWithMD5AndDES).generateSecret(pbeKeySpec);
    }
 
    private byte[] doCrypt(final byte[] cipher, final SecretKey secretKey, int mode) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
 
        final AlgorithmParameterSpec pbeParamSpec = new PBEParameterSpec(salt, iterations);
        final Cipher pbeCipher = Cipher.getInstance(PBEWithMD5AndDES);
 
        pbeCipher.init(mode, secretKey, pbeParamSpec);
        return pbeCipher.doFinal(cipher);
    }
 
    public byte[] encrypt(final String nachricht, final SecretKey secretKey) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException {
       
           
            return doCrypt(nachricht.getBytes(), secretKey, Cipher.ENCRYPT_MODE);
    }
 
    public String decrypt(final byte[] nachricht, final SecretKey secretKey) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
        return new String(doCrypt(nachricht, secretKey, Cipher.DECRYPT_MODE));
    }
 
//    public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, InvalidKeySpecException {
//
//        //final String plainText = "Hallo Welt1234xyz578zyx";
//        final String plainText = "Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.  Hallo, ich bin eine Testnachricht. Dies Nachricht darf auch länger sein.";
//        final String password = "secret";
//
//        final Encrypt encrypt = new Encrypt();
//        final SecretKey secretKey = encrypt.makeKeyFromPassword(password);
//
//        final byte[] cipher = encrypt.encrypt(plainText, secretKey);
//        final String decrypted = encrypt.decrypt(cipher, secretKey);
//
//        System.out.println(plainText.equals(decrypted) ? decrypted : "failed!");
//       
//        System.out.println();
//        System.out.println(new String(cipher));
//        System.out.println();
//        System.out.println(decrypted);
//    }
}

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