[Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Java crypto

Posted on 2011-02-13
8
Medium Priority
?
381 Views
Last Modified: 2012-05-11
String hashPassword = md5(arg4);

byte[] hPassword = AES.getAESKey(hashPassword, "888");
response = AES.encrypt(hPassword, "challenge");

//---------------------------------------------------------------------------------------

String driverHash = hashPassword;

byte[] driver_hash = AES.getAESKey(driverHash, "888");
String checkResponse = AES.decrypt(driver_hash, "challenge");

I compiled the codes. no error. Tried running the codes, I got a java.lang.NumberFormatException: For input string: "ch"

When I changed "challenge" to a single digit "1", it can run fine. Im stuck. What can be the problem??
0
Comment
Question by:moombaz
  • 4
  • 4
8 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 34883763
Sorry, I was trying to find this method getAESKey in Java Crypto API, and
somehow, I could not. What is the type of this AES in your code, or
is it a static method. But could not find class AES in Java Crypto either.

Most obvious general point is that it expects String which should be possible to be evaluated
as integer (so "1" will work and "challenge" would not, did you try some other number?),
 but this is certainly not too helpful.

Perhaps someone with experience in Crypto would advise.

Still if you elaborate a little bit on the context, maybe it will help.
0
 
LVL 1

Author Comment

by:moombaz
ID: 34884896
hi for_yan,

im using all of this

import java.io.*;
import java.net.*;
import java.util.*;
import java.text.*;
import cryptosystem.*;
import java.security.*;
0
 
LVL 47

Expert Comment

by:for_yan
ID: 34884914
So is AES a class within these packages or it is an instance
of some class? If the latter, then what is the class name?
I was looking for a method getAESKey in Java crypto
but it for some reason escapes me.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 47

Expert Comment

by:for_yan
ID: 34884944

Do you have a link to the API documentation for these classes?
Those which I see for Java crypto don't seem to contain this stuff.
Is getAESKey method something which is part of your program, not some method from API?
0
 
LVL 1

Author Comment

by:moombaz
ID: 34885037
No I just call it directly. Im not calling from another class or method
0
 
LVL 1

Author Comment

by:moombaz
ID: 34885043
ouh.. my bad.. it is from this class.

package cryptosystem;

import java.security.MessageDigest;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.KeyGenerator;

import java.security.NoSuchAlgorithmException;

public class AES {
	
	public static String asHex (byte buf[]){
		StringBuffer strbuf = new StringBuffer(buf.length*2);
		int i;
		
		for(i=0; i<buf.length;i++){
			if(((int) buf[i] & 0xff) < 0x10)
				strbuf.append("0");
			
			strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
		}
		return strbuf.toString();
	}
	
	public static byte[] asByte (String hex){
		byte[] bts = new byte[hex.length()/2];
		for(int i=0;i<bts.length;i++){
			bts[i] = (byte) Integer.parseInt(hex.substring(2*i, 2*i+2), 16);
		}
		
		return bts;
	}
	
	/* returns a 128 bit key */
	public static byte[] getAESKey(String password, String salt) 
													throws Exception{
		int IC = 2;
		byte[] keyBytes = null;
		
		MessageDigest md = MessageDigest.getInstance("MD5");
		md.update(password.getBytes("CP1252"));
		md.update(salt.getBytes("CP1252"));
		for(int i=1; i<IC; i++){
			md.update(md.digest());
		}
		
		keyBytes = md.digest();
		
		return keyBytes;
	}
	
	public static byte[] generateKey(){
		byte[] raw = null;
		try {
			KeyGenerator kgen = KeyGenerator.getInstance("AES");
			kgen.init(128);
			
			SecretKey skey = kgen.generateKey();
			raw = skey.getEncoded();
			
		}catch (NoSuchAlgorithmException e){
			System.out.println(e);
		}
		
		return raw;
	}
	
	public static String encrypt(byte[] key, String plainText) 
													throws Exception{
		byte[] encrypted = null;
		
		SecretKeySpec sKeySpec = new SecretKeySpec(key, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		
		cipher.init(Cipher.ENCRYPT_MODE, sKeySpec);
		
		encrypted = cipher.doFinal(plainText.getBytes());
		
		return asHex(encrypted);
	}
	
	public static String decrypt(byte[] key, String cipherText) 
													throws Exception{
		byte[] decrypted = null;
		
		SecretKeySpec sKeySpec = new SecretKeySpec(key, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		
		cipher.init(Cipher.DECRYPT_MODE, sKeySpec);
		
		decrypted = cipher.doFinal(asByte(cipherText));
		
		return new String(decrypted);
	}
	
	public static void main(String[] args) throws Exception {
		String message="This is just an example";
		String password = "apple1";
		String salt = "47BCE5C74F589F4867DBD57E9CA9F808";
		
		// Create a key
		byte[] key = getAESKey(password, salt);
		
		String hex = asHex(key);
		System.out.println("hex: "+hex+" Len:"+hex.getBytes().length);
		
		String hash = "48c27a623063a286358e0bf65bd5afbd";
		byte[] hashBytes = asByte(hash);
		
		boolean expected = java.util.Arrays.equals(hashBytes, key);
		System.out.println("Test " + (expected ? "SUCCEEDED!" : "FAILED!"));
		
		String encrypted = encrypt(key, message);
		System.out.println("encrypted: "+encrypted);
		
		String original = decrypt(hashBytes, encrypted);
		System.out.println("original: "+original);
	}
}

Open in new window

0
 
LVL 47

Accepted Solution

by:
for_yan earned 2000 total points
ID: 34885185
Is "challenge" - is something that you yourself specify?
As you understand I'm no specialist in this stuff, but looking at this code
it seems to me that it expects in this place the string which has only Hex number,
which means this string is a key which should be made up of digits and letters "a" through "f",
that's why "challenge"  which contains "h" and "l" and "g" causes problems.
If this is something you select yourself - try to select the key following this rule,
say 3a4b2345e should be fine, but 1t34s - is not good as "s" and "t" has no meaning in Hex number.
0
 
LVL 1

Author Comment

by:moombaz
ID: 34885663
I've tried and it doesnt work. "challenge" i replaced to "3a4b2345e". Error message that I got is javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16.

Still doesnt work. anw, i have been encrypting and decrypting using the same key. all of them works except for this one.
0

Featured Post

VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
In this post we will learn different types of Android Layout and some basics of an Android App.
Viewers learn about the scanner class in this video and are introduced to receiving user input for their programs. Additionally, objects, conditional statements, and loops are used to help reinforce the concepts. Introduce Scanner class: Importing…
Viewers learn how to read error messages and identify possible mistakes that could cause hours of frustration. Coding is as much about debugging your code as it is about writing it. Define Error Message: Line Numbers: Type of Error: Break Down…
Suggested Courses
Course of the Month20 days, 14 hours left to enroll

810 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question