Exception in thread "main" java.lang.NullPointerException

[yvprashant]

Am trying a program to encrypt a string using 3DES.

Source code of the program -

import java.util.*;
import javax.crypto.*;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import java.security.*;
public class TripleDESTest {
public static void main(String[] args) throws Exception {
String text = "kyle boon";
byte[] codedtext = new TripleDESTest().encrypt(text);
String decodedtext = new TripleDESTest().decrypt(codedtext);
System.out.println(codedtext);
System.out.println(decodedtext); // This correctly shows "kyle boon"

}
public byte[] encrypt(String message) throws Exception {
MessageDigest md = null;
final byte[] digestOfPassword = md.digest("HG58YZ3CR9"
.getBytes("utf-8"));
final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
for (int j = 0, k = 16; j < 8;) {
keyBytes[k++] = keyBytes[j++];
}
final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
final Cipher cipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key, iv);
final byte[] plainTextBytes = message.getBytes("utf-8");
final byte[] cipherText = cipher.doFinal(plainTextBytes);
// final String encodedCipherText = new sun.misc.BASE64Encoder()
// .encode(cipherText);
return cipherText;
}
public String decrypt(byte[] message) throws Exception {
final MessageDigest md = MessageDigest.getInstance("md5");
final byte[] digestOfPassword = md.digest("HG58YZ3CR9"
.getBytes("utf-8"));
final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
for (int j = 0, k = 16; j < 8;) {
keyBytes[k++] = keyBytes[j++];
}
final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
final Cipher decipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
decipher.init(Cipher.DECRYPT_MODE, key, iv);
// final byte[] encData = new
// sun.misc.BASE64Decoder().decodeBuffer(message);
final byte[] plainText = decipher.doFinal(message);
return new String(plainText, "UTF-8");
}
}

Error details -
Exception in thread "main" java.lang.NullPointerException
at TripleDESTest.encrypt(TripleDESTest.java:18)
at TripleDESTest.main(TripleDESTest.java:10)

Any help would be greatly appreciated. Thank you. :)

[eRaaaa]

MessageDigest md = null;
final byte[] digestOfPassword = md.digest("HG58YZ3CR9".getBytes("utf-8"));

md is null and in the nex tline you are calling a method on it --> NPE!

MessageDigest md = MessageDigest.getInstance("...."); <---

[yvprashant]

ah! right!

Am a beginner in java programming.
Can you tell me how do i correct this?

[eRaaaa]

I already have?
MessageDigest md = MessageDigest.getInstance(algorithm HERE, such as "SHA");

Take a look at:
MessageDigest (Java Platform SE 6)

[yvprashant]

Thanks!
But now am getting this error -

Exception in thread "main" javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.DESedeCipher.engineDoFinal (DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)
at TripleDESTest.decrypt(TripleDESTest.java:47)
at TripleDESTest.main(TripleDESTest.java:11)

[Jhovarie]

java.lang.NullPointerException reason is that you are accessing object that is not exist or your code cant access the object.

example

YourObjectClass MyVar = null; //<- null pointers
then you are invoking "var" //then this will cause "java.lang.NullPointerException"

the code bellow is not null.
YourObjectClass MyVar = new YourObjectClass() //<- this is not null.

[yvprashant]

Thanks! :)
Got it :)