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currently the program is listing the planets in a solar system. each planet entered to the solarsystem has a position counter adding position++
after all the planets are listed I want to SystemPrintln a statement saying, There are this many planets in your solar system. Should I not be able to just return position; for this?
At this point the result is in a toString so to add this final line stating the number of planets how would I do this?
Could I add a second method "position" to the toString?
can I just return position in a system.out.println statement from the drive class?
class Planet:
package planets;
public class Planet {
String name;
int moons;
public Planet(String name, int moons)
{
this.moons = moons;
this.name = name;
}
public String toString() {
return "The Planet " + name + " Has " + moons + " Moon(s) \r\n ";
}
}
Class SolarSystem:
package planets;
public class SolarSystem {
private Planet[]planets;
private int position = 0;
public SolarSystem(int size) {
planets = new Planet[size];
}
public void add(Planet planet) {
planets[position] = planet;
position++;
}
public String toString(){
String result = "";
for(int i = 0; i < planets.length; i++){
result += planets[i].toString();
}
return result;
}
}
Class Driver:
package planets;
public class Driver {
public static void main(String[]args) {
Planet mercury = new Planet ("Mercury", 0);
Planet venus = new Planet ("Venus", 0);
Planet earth = new Planet ("Earth", 1);
Planet mars = new Planet ("Mars", 2);
Planet jupiter = new Planet ("Jupiter", 67);
Planet saturn = new Planet ("Saturn", 62);
Planet uranus = new Planet ("Uranus", 27);
Planet neptune = new Planet ("Neptune", 14);
Planet pluto = new Planet ("Pluto", 5);
SolarSystem solarSystem = new SolarSystem(9);
solarSystem.add(mercury);
solarSystem.add(venus);
solarSystem.add(earth);
solarSystem.add(mars);
solarSystem.add(jupiter);
solarSystem.add(saturn);
solarSystem.add(uranus);
solarSystem.add(neptune);
solarSystem.add(pluto);
System.out.println(solarSystem);
}
}
For your class you have to return the position variabel.
public int sumPlanets(){
return position;
}
and in your method toString use :
public String toString(){
return Integer.toString(sumPlanets());
}
but i recommend only use the position for return the total elements
public String toString(){
return position;
}
In your in your code :
package planets;
public class SolarSystem {
private Planet[]planets;
private int position = 0;
public SolarSystem(int size) {
planets = new Planet[size];
}
public void add(Planet planet) {
planets[position] = planet;
position++;
}
public String toString(){
return Integer.toString(sumPlanets());
}
public int sumPlanets(){
return position;
}
}
In order to print out the total number of planets I used the position variable which adds one each time a planets object is made.
position++
so to print this I added
System.out.println("You Have " + position + " Planets In Your Solar System");
Directly after the loop so It would be printed out one time with the total amount.
The full class ended up like this.
package planets;
public class SolarSystem {
private Planet[]planets;
private int position = 0;
public SolarSystem(int size) {
planets = new Planet[size];
}
public void add(Planet planet) {
planets[position] = planet;
position++;
}
public String toString(){
String result = "";
for(int i = 0; i < planets.length; i++){
result += planets[i].toString();
}
System.out.println("You Have " + position + " Planets In Your Solar System");
return result;
}
}
I am planning to make an airline system. I have initialized the array using initSeats but it still throws back the NPE error. It happens when i call the seatChecker() from bookMenu.
public void initSeats(){
for(int b = 0; b < seatList.length; b++)
{
initC.setName("null");
initC.setEmail("null");
initC.setCreditNo(0);
initC.setAddress("null");
initC.setPassportNo("null");
seatList[b] = new Seat('A', 0, "null", 0.0, "Available", initC);
}
for(int d = 0; d <= 24; d++)
{
seatList[d].setSeatLetter('A');
seatList[d].setSeatNo(d);
}
for(int n = 25; n <= 48; n++)
{
seatList[n].setSeatLetter('B');
seatList[n].setSeatNo(n);
}
for(int m = 49; m <= 72; m++)
{
seatList[m].setSeatLetter('C');
seatList[m].setSeatNo(m);
}
for(int t = 73; t <= 96; t++)
{
seatList[t].setSeatLetter('D');
seatList[t].setSeatNo(t);
}
for(int q = 97; q <= 120; q++)
{
seatList[q].setSeatLetter('E');
seatList[q].setSeatNo(q);
}
for(int v = 121; v < 144; v++)
{
seatList[v].setSeatLetter('F');
seatList[v].setSeatNo(v);
}
for(int x = 0; x <= 48; x++)
{
seatList[x].setSection("Front");
seatList[x].setPrice(500);
}
for(int j = 49; j <= 96; j++)
{
seatList[j].setSection("Middle");
seatList[j].setPrice(250);
}
for(int u = 97; u < 144; u++)
{
seatList[u].setSection("Back");
seatList[u].setPrice(100);
}
}
public void seatChecker(int index)
{
String status = seatList[index].getStatus();
if(status.equalsIgnoreCase("Available")){
System.out.println("Seat is Available.");
}else{
System.out.println("Seat is not Available. Please Pick Another Seat.");
bookMenu();
}
}
public void bookMenu()
{
int choice1 = 0;
int index;
System.out.println("Where do you want to be seated?");
System.out.println("[1] Front");
System.out.println("[2] Middle");
System.out.println("[3] Back");
choice1 = sc.nextInt();
sc.nextLine();
if(choice1 == 1){
System.out.print("Choose a seat number (0 - 48): ");
index = sc.nextInt();
sc.nextLine();
seatChecker(index);
}else if(choice1 == 2){
System.out.println("Choose a seat number (49 - 96): ");
index = sc.nextInt();
sc.nextLine();
seatChecker(index);
}else if(choice1 == 3){
System.out.println("Choose a seat number (97 - 144): ");
index = sc.nextInt();
sc.nextLine();
seatChecker(index);
}else
{
System.out.println("Invalid Choice. Going back to Menu.");
MainMenu();
}
}
Null Pointer Exception Code
Exception in thread "main" java.lang.NullPointerException
at pkg.Airlines.AirlineUI.seatChecker(AirlineUI.java:132)
Seat Class
public class Seat{
private char seatLetter;
private int seatNo;
private String section;
private double price;
private String status;
private Customer customerDetails;
public Seat(char seatLetter, int seatNo, String section, double price, String status, Customer details)
{
this.seatLetter = seatLetter;
this.seatNo = seatNo;
this.section = section;
this.price = price;
this.status = status;
this.customerDetails = details;
}
public Customer getCustomerDetails() {
return customerDetails;
}
public void setCustomerDetails(Customer customerDetails) {
this.customerDetails = customerDetails;
}
public char getSeatLetter() {
return seatLetter;
}
public void setSeatLetter(char seatLetter) {
this.seatLetter = seatLetter;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public int getSeatNo() {
return seatNo;
}
public void setSeatNo(int seatNo) {
this.seatNo = seatNo;
}
public String getSection() {
return section;
}
public void setSection(String section) {
this.section = section;
}
}
Probably the problems are this two line :
String status = seatList[index].getStatus();
if(status.equalsIgnoreCase("Available"))
First thing could be seatList[index] is not initialized . Once you declare an array of references as :
Seat[] array = new Seat[10];
The array contains 10 null references for Seat object . You need to instantiate them before using them :
Seat[0] = new Seat();
Second potential problem will be, this check :
if(status.equalsIgnoreCase("Available"))
Replace it to :
if("Available".equalsIgnoreCase(status))
to avoid any NullPointerException in case status is null.
P.S. Please show us the Seat class to understand your problem better.
Well is quite simple resolve a Null Pointer Exception.
Probably in one of the index of seatList there isn't a value.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Is it possible to decrypt md5 hashes?
Is it possible to get a string from MD5 in Java?
Firstly a string is converted to MD5 checksum, is it possible to get this MD5 checksum back to the original text?
I'm assuming you use MessageDigest, any help is greatly appreciated, even other java libraries.
Just want to also point out on if it not possible how this app is able to it: https://play.google.com/store/apps/details?id=com.fab.md5&hl=en
I even converted some text to MD5 checksum using another application and used this checksum to see if the app was able to convert it back to text and it did.
No, that's not really possible, as
there can be more than one string giving the same MD5
it was designed to be hard to "reverse"
The goal of the MD5 and its family of hashing functions is
to get short "extracts" from long string
to make it hard to guess where they come from
to make it hard to find collisions, that is other words having the same hash (which is a very similar exigence as the second one)
Think that you can get the MD5 of any string, even very long. And the MD5 is only 16 bytes long (32 if you write it in hexa to store or distribute it more easily). If you could reverse them, you'd have a magical compacting scheme.
This being said, as there aren't so many short strings (passwords...) used in the world, you can test them from a dictionary (that's called "brute force attack") or even google for your MD5. If the word is common and wasn't salted, you have a reasonable chance to succeed...
Its not possible thats the whole point of hashing. You can however bruteforce by going through all possibilities (using all possible digits characters in every possible order) and hashing them and checking for a collision.
for more information on hashing and MD5 etc see: http://en.wikipedia.org/wiki/MD5 , http://en.wikipedia.org/wiki/Hash_function , http://en.wikipedia.org/wiki/Cryptographic_hash_function and http://onin.com/hhh/hhhexpl.html
I myself created my own app to do this, its open source you can check the link: http://sourceforge.net/projects/jpassrecovery/ and of course the source. Here is the source for easy access it has a basic implementation in the comments:
Bruter.java:
import java.util.ArrayList;
public class Bruter {
public ArrayList<String> characters = new ArrayList<>();
public boolean found = false;
public int maxLength;
public int minLength;
public int count;
long starttime, endtime;
public int minutes, seconds, hours, days;
public char[] specialCharacters = {'~', '`', '!', '#', '#', '$', '%', '^',
'&', '*', '(', ')', '_', '-', '+', '=', '{', '}', '[', ']', '|', '\\',
';', ':', '\'', '"', '<', '.', ',', '>', '/', '?', ' '};
public boolean done = false;
public boolean paused = false;
public boolean isFound() {
return found;
}
public void setPaused(boolean paused) {
this.paused = paused;
}
public boolean isPaused() {
return paused;
}
public void setFound(boolean found) {
this.found = found;
}
public synchronized void setEndtime(long endtime) {
this.endtime = endtime;
}
public int getCounter() {
return count;
}
public long getRemainder() {
return getNumberOfPossibilities() - count;
}
public long getNumberOfPossibilities() {
long possibilities = 0;
for (int i = minLength; i <= maxLength; i++) {
possibilities += (long) Math.pow(characters.size(), i);
}
return possibilities;
}
public void addExtendedSet() {
for (char c = (char) 0; c <= (char) 31; c++) {
characters.add(String.valueOf(c));
}
}
public void addStandardCharacterSet() {
for (char c = (char) 32; c <= (char) 127; c++) {
characters.add(String.valueOf(c));
}
}
public void addLowerCaseLetters() {
for (char c = 'a'; c <= 'z'; c++) {
characters.add(String.valueOf(c));
}
}
public void addDigits() {
for (int c = 0; c <= 9; c++) {
characters.add(String.valueOf(c));
}
}
public void addUpperCaseLetters() {
for (char c = 'A'; c <= 'Z'; c++) {
characters.add(String.valueOf(c));
}
}
public void addSpecialCharacters() {
for (char c : specialCharacters) {
characters.add(String.valueOf(c));
}
}
public void setMaxLength(int i) {
maxLength = i;
}
public void setMinLength(int i) {
minLength = i;
}
public int getPerSecond() {
int i;
try {
i = (int) (getCounter() / calculateTimeDifference());
} catch (Exception ex) {
return 0;
}
return i;
}
public String calculateTimeElapsed() {
long timeTaken = calculateTimeDifference();
seconds = (int) timeTaken;
if (seconds > 60) {
minutes = (int) (seconds / 60);
if (minutes * 60 > seconds) {
minutes = minutes - 1;
}
if (minutes > 60) {
hours = (int) minutes / 60;
if (hours * 60 > minutes) {
hours = hours - 1;
}
}
if (hours > 24) {
days = (int) hours / 24;
if (days * 24 > hours) {
days = days - 1;
}
}
seconds -= (minutes * 60);
minutes -= (hours * 60);
hours -= (days * 24);
days -= (hours * 24);
}
return "Time elapsed: " + days + "days " + hours + "h " + minutes + "min " + seconds + "s";
}
private long calculateTimeDifference() {
long timeTaken = (long) ((endtime - starttime) * (1 * Math.pow(10, -9)));
return timeTaken;
}
public boolean excludeChars(String s) {
char[] arrayChars = s.toCharArray();
for (int i = 0; i < arrayChars.length; i++) {
characters.remove(arrayChars[i] + "");
}
if (characters.size() < maxLength) {
return false;
} else {
return true;
}
}
public int getMaxLength() {
return maxLength;
}
public int getMinLength() {
return minLength;
}
public void setIsDone(Boolean b) {
done = b;
}
public boolean isDone() {
return done;
}
}
HashBruter.java:
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.zip.Adler32;
import java.util.zip.CRC32;
import java.util.zip.Checksum;
import javax.swing.JOptionPane;
public class HashBruter extends Bruter {
/*
* public static void main(String[] args) {
*
* final HashBruter hb = new HashBruter();
*
* hb.setMaxLength(5); hb.setMinLength(1);
*
* hb.addSpecialCharacters(); hb.addUpperCaseLetters();
* hb.addLowerCaseLetters(); hb.addDigits();
*
* hb.setType("sha-512");
*
* hb.setHash("282154720ABD4FA76AD7CD5F8806AA8A19AEFB6D10042B0D57A311B86087DE4DE3186A92019D6EE51035106EE088DC6007BEB7BE46994D1463999968FBE9760E");
*
* Thread thread = new Thread(new Runnable() {
*
* #Override public void run() { hb.tryBruteForce(); } });
*
* thread.start();
*
* while (!hb.isFound()) { System.out.println("Hash: " +
* hb.getGeneratedHash()); System.out.println("Number of Possibilities: " +
* hb.getNumberOfPossibilities()); System.out.println("Checked hashes: " +
* hb.getCounter()); System.out.println("Estimated hashes left: " +
* hb.getRemainder()); }
*
* System.out.println("Found " + hb.getType() + " hash collision: " +
* hb.getGeneratedHash() + " password is: " + hb.getPassword());
*
* }
*/
public String hash, generatedHash, password;
public String type;
public String getType() {
return type;
}
public String getPassword() {
return password;
}
public void setHash(String p) {
hash = p;
}
public void setType(String digestType) {
type = digestType;
}
public String getGeneratedHash() {
return generatedHash;
}
public void tryBruteForce() {
starttime = System.nanoTime();
for (int size = minLength; size <= maxLength; size++) {
if (found == true || done == true) {
break;
} else {
while (paused) {
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
generateAllPossibleCombinations("", size);
}
}
done = true;
}
private void generateAllPossibleCombinations(String baseString, int length) {
while (paused) {
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
if (found == false || done == false) {
if (baseString.length() == length) {
if(type.equalsIgnoreCase("crc32")) {
generatedHash = generateCRC32(baseString);
} else if(type.equalsIgnoreCase("adler32")) {
generatedHash = generateAdler32(baseString);
} else if(type.equalsIgnoreCase("crc16")) {
generatedHash=generateCRC16(baseString);
} else if(type.equalsIgnoreCase("crc64")) {
generatedHash=generateCRC64(baseString.getBytes());
}
else {
generatedHash = generateHash(baseString.toCharArray());
}
password = baseString;
if (hash.equals(generatedHash)) {
password = baseString;
found = true;
done = true;
}
count++;
} else if (baseString.length() < length) {
for (int n = 0; n < characters.size(); n++) {
generateAllPossibleCombinations(baseString + characters.get(n), length);
}
}
}
}
private String generateHash(char[] passwordChar) {
MessageDigest md = null;
try {
md = MessageDigest.getInstance(type);
} catch (NoSuchAlgorithmException e1) {
JOptionPane.showMessageDialog(null, "No such algorithm for hashes exists", "Error", JOptionPane.ERROR_MESSAGE);
}
String passwordString = new String(passwordChar);
byte[] passwordByte = passwordString.getBytes();
md.update(passwordByte, 0, passwordByte.length);
byte[] encodedPassword = md.digest();
String encodedPasswordInString = toHexString(encodedPassword);
return encodedPasswordInString;
}
private void byte2hex(byte b, StringBuffer buf) {
char[] hexChars = {'0', '1', '2', '3', '4', '5', '6', '7', '8',
'9', 'A', 'B', 'C', 'D', 'E', 'F'};
int high = ((b & 0xf0) >> 4);
int low = (b & 0x0f);
buf.append(hexChars[high]);
buf.append(hexChars[low]);
}
private String toHexString(byte[] block) {
StringBuffer buf = new StringBuffer();
int len = block.length;
for (int i = 0; i < len; i++) {
byte2hex(block[i], buf);
}
return buf.toString();
}
private String generateCRC32(String baseString) {
//Convert string to bytes
byte bytes[] = baseString.getBytes();
Checksum checksum = new CRC32();
/*
* To compute the CRC32 checksum for byte array, use
*
* void update(bytes[] b, int start, int length)
* method of CRC32 class.
*/
checksum.update(bytes,0,bytes.length);
/*
* Get the generated checksum using
* getValue method of CRC32 class.
*/
return String.valueOf(checksum.getValue());
}
private String generateAdler32(String baseString) {
//Convert string to bytes
byte bytes[] = baseString.getBytes();
Checksum checksum = new Adler32();
/*
* To compute the CRC32 checksum for byte array, use
*
* void update(bytes[] b, int start, int length)
* method of CRC32 class.
*/
checksum.update(bytes,0,bytes.length);
/*
* Get the generated checksum using
* getValue method of CRC32 class.
*/
return String.valueOf(checksum.getValue());
}
/*************************************************************************
* Compilation: javac CRC16.java
* Execution: java CRC16 s
*
* Reads in a string s as a command-line argument, and prints out
* its 16-bit Cyclic Redundancy Check (CRC16). Uses a lookup table.
*
* Reference: http://www.gelato.unsw.edu.au/lxr/source/lib/crc16.c
*
* % java CRC16 123456789
* CRC16 = bb3d
*
* Uses irreducible polynomial: 1 + x^2 + x^15 + x^16
*
*
*************************************************************************/
private String generateCRC16(String baseString) {
int[] table = {
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
};
byte[] bytes = baseString.getBytes();
int crc = 0x0000;
for (byte b : bytes) {
crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
}
return Integer.toHexString(crc);
}
/*******************************************************************************
* Copyright (c) 2009, 2012 Mountainminds GmbH & Co. KG and Contributors
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Marc R. Hoffmann - initial API and implementation
*
*******************************************************************************/
/**
* CRC64 checksum calculator based on the polynom specified in ISO 3309. The
* implementation is based on the following publications:
*
* <ul>
* <li>http://en.wikipedia.org/wiki/Cyclic_redundancy_check</li>
* <li>http://www.geocities.com/SiliconValley/Pines/8659/crc.htm</li>
* </ul>
*/
private static final long POLY64REV = 0xd800000000000000L;
private static final long[] LOOKUPTABLE;
static {
LOOKUPTABLE = new long[0x100];
for (int i = 0; i < 0x100; i++) {
long v = i;
for (int j = 0; j < 8; j++) {
if ((v & 1) == 1) {
v = (v >>> 1) ^ POLY64REV;
} else {
v = (v >>> 1);
}
}
LOOKUPTABLE[i] = v;
}
}
/**
* Calculates the CRC64 checksum for the given data array.
*
* #param data
* data to calculate checksum for
* #return checksum value
*/
public static String generateCRC64(final byte[] data) {
long sum = 0;
for (int i = 0; i < data.length; i++) {
final int lookupidx = ((int) sum ^ data[i]) & 0xff;
sum = (sum >>> 8) ^ LOOKUPTABLE[lookupidx];
}
return String.valueOf(sum);
}
}
you would use it like:
final HashBruter hb = new HashBruter();
hb.setMaxLength(5); hb.setMinLength(1);
hb.addSpecialCharacters(); hb.addUpperCaseLetters();
hb.addLowerCaseLetters(); hb.addDigits();
hb.setType("sha-512");
hb.setHash("282154720ABD4FA76AD7CD5F8806AA8A19AEFB6D10042B0D57A311B86087DE4DE3186A92019D6EE51035106EE088DC6007BEB7BE46994D1463999968FBE9760E");
Thread thread = new Thread(new Runnable() {
#Override public void run() { hb.tryBruteForce(); } });
thread.start();
while (!hb.isFound()) { System.out.println("Hash: " +
hb.getGeneratedHash()); System.out.println("Number of Possibilities: " +
hb.getNumberOfPossibilities()); System.out.println("Checked hashes: " +
hb.getCounter()); System.out.println("Estimated hashes left: " +
hb.getRemainder()); }
System.out.println("Found " + hb.getType() + " hash collision: " +
hb.getGeneratedHash() + " password is: " + hb.getPassword());
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Is it possible to decrypt md5 hashes?
Is it possible to get a string from MD5 in Java?
Firstly a string is converted to MD5 checksum, is it possible to get this MD5 checksum back to the original text?
I'm assuming you use MessageDigest, any help is greatly appreciated, even other java libraries.
Just want to also point out on if it not possible how this app is able to it: https://play.google.com/store/apps/details?id=com.fab.md5&hl=en
I even converted some text to MD5 checksum using another application and used this checksum to see if the app was able to convert it back to text and it did.
No, that's not really possible, as
there can be more than one string giving the same MD5
it was designed to be hard to "reverse"
The goal of the MD5 and its family of hashing functions is
to get short "extracts" from long string
to make it hard to guess where they come from
to make it hard to find collisions, that is other words having the same hash (which is a very similar exigence as the second one)
Think that you can get the MD5 of any string, even very long. And the MD5 is only 16 bytes long (32 if you write it in hexa to store or distribute it more easily). If you could reverse them, you'd have a magical compacting scheme.
This being said, as there aren't so many short strings (passwords...) used in the world, you can test them from a dictionary (that's called "brute force attack") or even google for your MD5. If the word is common and wasn't salted, you have a reasonable chance to succeed...
Its not possible thats the whole point of hashing. You can however bruteforce by going through all possibilities (using all possible digits characters in every possible order) and hashing them and checking for a collision.
for more information on hashing and MD5 etc see: http://en.wikipedia.org/wiki/MD5 , http://en.wikipedia.org/wiki/Hash_function , http://en.wikipedia.org/wiki/Cryptographic_hash_function and http://onin.com/hhh/hhhexpl.html
I myself created my own app to do this, its open source you can check the link: http://sourceforge.net/projects/jpassrecovery/ and of course the source. Here is the source for easy access it has a basic implementation in the comments:
Bruter.java:
import java.util.ArrayList;
public class Bruter {
public ArrayList<String> characters = new ArrayList<>();
public boolean found = false;
public int maxLength;
public int minLength;
public int count;
long starttime, endtime;
public int minutes, seconds, hours, days;
public char[] specialCharacters = {'~', '`', '!', '#', '#', '$', '%', '^',
'&', '*', '(', ')', '_', '-', '+', '=', '{', '}', '[', ']', '|', '\\',
';', ':', '\'', '"', '<', '.', ',', '>', '/', '?', ' '};
public boolean done = false;
public boolean paused = false;
public boolean isFound() {
return found;
}
public void setPaused(boolean paused) {
this.paused = paused;
}
public boolean isPaused() {
return paused;
}
public void setFound(boolean found) {
this.found = found;
}
public synchronized void setEndtime(long endtime) {
this.endtime = endtime;
}
public int getCounter() {
return count;
}
public long getRemainder() {
return getNumberOfPossibilities() - count;
}
public long getNumberOfPossibilities() {
long possibilities = 0;
for (int i = minLength; i <= maxLength; i++) {
possibilities += (long) Math.pow(characters.size(), i);
}
return possibilities;
}
public void addExtendedSet() {
for (char c = (char) 0; c <= (char) 31; c++) {
characters.add(String.valueOf(c));
}
}
public void addStandardCharacterSet() {
for (char c = (char) 32; c <= (char) 127; c++) {
characters.add(String.valueOf(c));
}
}
public void addLowerCaseLetters() {
for (char c = 'a'; c <= 'z'; c++) {
characters.add(String.valueOf(c));
}
}
public void addDigits() {
for (int c = 0; c <= 9; c++) {
characters.add(String.valueOf(c));
}
}
public void addUpperCaseLetters() {
for (char c = 'A'; c <= 'Z'; c++) {
characters.add(String.valueOf(c));
}
}
public void addSpecialCharacters() {
for (char c : specialCharacters) {
characters.add(String.valueOf(c));
}
}
public void setMaxLength(int i) {
maxLength = i;
}
public void setMinLength(int i) {
minLength = i;
}
public int getPerSecond() {
int i;
try {
i = (int) (getCounter() / calculateTimeDifference());
} catch (Exception ex) {
return 0;
}
return i;
}
public String calculateTimeElapsed() {
long timeTaken = calculateTimeDifference();
seconds = (int) timeTaken;
if (seconds > 60) {
minutes = (int) (seconds / 60);
if (minutes * 60 > seconds) {
minutes = minutes - 1;
}
if (minutes > 60) {
hours = (int) minutes / 60;
if (hours * 60 > minutes) {
hours = hours - 1;
}
}
if (hours > 24) {
days = (int) hours / 24;
if (days * 24 > hours) {
days = days - 1;
}
}
seconds -= (minutes * 60);
minutes -= (hours * 60);
hours -= (days * 24);
days -= (hours * 24);
}
return "Time elapsed: " + days + "days " + hours + "h " + minutes + "min " + seconds + "s";
}
private long calculateTimeDifference() {
long timeTaken = (long) ((endtime - starttime) * (1 * Math.pow(10, -9)));
return timeTaken;
}
public boolean excludeChars(String s) {
char[] arrayChars = s.toCharArray();
for (int i = 0; i < arrayChars.length; i++) {
characters.remove(arrayChars[i] + "");
}
if (characters.size() < maxLength) {
return false;
} else {
return true;
}
}
public int getMaxLength() {
return maxLength;
}
public int getMinLength() {
return minLength;
}
public void setIsDone(Boolean b) {
done = b;
}
public boolean isDone() {
return done;
}
}
HashBruter.java:
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.zip.Adler32;
import java.util.zip.CRC32;
import java.util.zip.Checksum;
import javax.swing.JOptionPane;
public class HashBruter extends Bruter {
/*
* public static void main(String[] args) {
*
* final HashBruter hb = new HashBruter();
*
* hb.setMaxLength(5); hb.setMinLength(1);
*
* hb.addSpecialCharacters(); hb.addUpperCaseLetters();
* hb.addLowerCaseLetters(); hb.addDigits();
*
* hb.setType("sha-512");
*
* hb.setHash("282154720ABD4FA76AD7CD5F8806AA8A19AEFB6D10042B0D57A311B86087DE4DE3186A92019D6EE51035106EE088DC6007BEB7BE46994D1463999968FBE9760E");
*
* Thread thread = new Thread(new Runnable() {
*
* #Override public void run() { hb.tryBruteForce(); } });
*
* thread.start();
*
* while (!hb.isFound()) { System.out.println("Hash: " +
* hb.getGeneratedHash()); System.out.println("Number of Possibilities: " +
* hb.getNumberOfPossibilities()); System.out.println("Checked hashes: " +
* hb.getCounter()); System.out.println("Estimated hashes left: " +
* hb.getRemainder()); }
*
* System.out.println("Found " + hb.getType() + " hash collision: " +
* hb.getGeneratedHash() + " password is: " + hb.getPassword());
*
* }
*/
public String hash, generatedHash, password;
public String type;
public String getType() {
return type;
}
public String getPassword() {
return password;
}
public void setHash(String p) {
hash = p;
}
public void setType(String digestType) {
type = digestType;
}
public String getGeneratedHash() {
return generatedHash;
}
public void tryBruteForce() {
starttime = System.nanoTime();
for (int size = minLength; size <= maxLength; size++) {
if (found == true || done == true) {
break;
} else {
while (paused) {
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
generateAllPossibleCombinations("", size);
}
}
done = true;
}
private void generateAllPossibleCombinations(String baseString, int length) {
while (paused) {
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
if (found == false || done == false) {
if (baseString.length() == length) {
if(type.equalsIgnoreCase("crc32")) {
generatedHash = generateCRC32(baseString);
} else if(type.equalsIgnoreCase("adler32")) {
generatedHash = generateAdler32(baseString);
} else if(type.equalsIgnoreCase("crc16")) {
generatedHash=generateCRC16(baseString);
} else if(type.equalsIgnoreCase("crc64")) {
generatedHash=generateCRC64(baseString.getBytes());
}
else {
generatedHash = generateHash(baseString.toCharArray());
}
password = baseString;
if (hash.equals(generatedHash)) {
password = baseString;
found = true;
done = true;
}
count++;
} else if (baseString.length() < length) {
for (int n = 0; n < characters.size(); n++) {
generateAllPossibleCombinations(baseString + characters.get(n), length);
}
}
}
}
private String generateHash(char[] passwordChar) {
MessageDigest md = null;
try {
md = MessageDigest.getInstance(type);
} catch (NoSuchAlgorithmException e1) {
JOptionPane.showMessageDialog(null, "No such algorithm for hashes exists", "Error", JOptionPane.ERROR_MESSAGE);
}
String passwordString = new String(passwordChar);
byte[] passwordByte = passwordString.getBytes();
md.update(passwordByte, 0, passwordByte.length);
byte[] encodedPassword = md.digest();
String encodedPasswordInString = toHexString(encodedPassword);
return encodedPasswordInString;
}
private void byte2hex(byte b, StringBuffer buf) {
char[] hexChars = {'0', '1', '2', '3', '4', '5', '6', '7', '8',
'9', 'A', 'B', 'C', 'D', 'E', 'F'};
int high = ((b & 0xf0) >> 4);
int low = (b & 0x0f);
buf.append(hexChars[high]);
buf.append(hexChars[low]);
}
private String toHexString(byte[] block) {
StringBuffer buf = new StringBuffer();
int len = block.length;
for (int i = 0; i < len; i++) {
byte2hex(block[i], buf);
}
return buf.toString();
}
private String generateCRC32(String baseString) {
//Convert string to bytes
byte bytes[] = baseString.getBytes();
Checksum checksum = new CRC32();
/*
* To compute the CRC32 checksum for byte array, use
*
* void update(bytes[] b, int start, int length)
* method of CRC32 class.
*/
checksum.update(bytes,0,bytes.length);
/*
* Get the generated checksum using
* getValue method of CRC32 class.
*/
return String.valueOf(checksum.getValue());
}
private String generateAdler32(String baseString) {
//Convert string to bytes
byte bytes[] = baseString.getBytes();
Checksum checksum = new Adler32();
/*
* To compute the CRC32 checksum for byte array, use
*
* void update(bytes[] b, int start, int length)
* method of CRC32 class.
*/
checksum.update(bytes,0,bytes.length);
/*
* Get the generated checksum using
* getValue method of CRC32 class.
*/
return String.valueOf(checksum.getValue());
}
/*************************************************************************
* Compilation: javac CRC16.java
* Execution: java CRC16 s
*
* Reads in a string s as a command-line argument, and prints out
* its 16-bit Cyclic Redundancy Check (CRC16). Uses a lookup table.
*
* Reference: http://www.gelato.unsw.edu.au/lxr/source/lib/crc16.c
*
* % java CRC16 123456789
* CRC16 = bb3d
*
* Uses irreducible polynomial: 1 + x^2 + x^15 + x^16
*
*
*************************************************************************/
private String generateCRC16(String baseString) {
int[] table = {
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
};
byte[] bytes = baseString.getBytes();
int crc = 0x0000;
for (byte b : bytes) {
crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
}
return Integer.toHexString(crc);
}
/*******************************************************************************
* Copyright (c) 2009, 2012 Mountainminds GmbH & Co. KG and Contributors
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Marc R. Hoffmann - initial API and implementation
*
*******************************************************************************/
/**
* CRC64 checksum calculator based on the polynom specified in ISO 3309. The
* implementation is based on the following publications:
*
* <ul>
* <li>http://en.wikipedia.org/wiki/Cyclic_redundancy_check</li>
* <li>http://www.geocities.com/SiliconValley/Pines/8659/crc.htm</li>
* </ul>
*/
private static final long POLY64REV = 0xd800000000000000L;
private static final long[] LOOKUPTABLE;
static {
LOOKUPTABLE = new long[0x100];
for (int i = 0; i < 0x100; i++) {
long v = i;
for (int j = 0; j < 8; j++) {
if ((v & 1) == 1) {
v = (v >>> 1) ^ POLY64REV;
} else {
v = (v >>> 1);
}
}
LOOKUPTABLE[i] = v;
}
}
/**
* Calculates the CRC64 checksum for the given data array.
*
* #param data
* data to calculate checksum for
* #return checksum value
*/
public static String generateCRC64(final byte[] data) {
long sum = 0;
for (int i = 0; i < data.length; i++) {
final int lookupidx = ((int) sum ^ data[i]) & 0xff;
sum = (sum >>> 8) ^ LOOKUPTABLE[lookupidx];
}
return String.valueOf(sum);
}
}
you would use it like:
final HashBruter hb = new HashBruter();
hb.setMaxLength(5); hb.setMinLength(1);
hb.addSpecialCharacters(); hb.addUpperCaseLetters();
hb.addLowerCaseLetters(); hb.addDigits();
hb.setType("sha-512");
hb.setHash("282154720ABD4FA76AD7CD5F8806AA8A19AEFB6D10042B0D57A311B86087DE4DE3186A92019D6EE51035106EE088DC6007BEB7BE46994D1463999968FBE9760E");
Thread thread = new Thread(new Runnable() {
#Override public void run() { hb.tryBruteForce(); } });
thread.start();
while (!hb.isFound()) { System.out.println("Hash: " +
hb.getGeneratedHash()); System.out.println("Number of Possibilities: " +
hb.getNumberOfPossibilities()); System.out.println("Checked hashes: " +
hb.getCounter()); System.out.println("Estimated hashes left: " +
hb.getRemainder()); }
System.out.println("Found " + hb.getType() + " hash collision: " +
hb.getGeneratedHash() + " password is: " + hb.getPassword());
I am trying to modify the merge sort algorithm to sort an array of strings in lexicographic order, I am not really advanced so I may be making some newbie mistakes. This is the main and the tester and the mergesorter.
public class MergeSorter
{
private int[] a;
private int[] left_side;
private int[] right_side;
public MergeSorter(int[] anArray)
{
a = anArray;
}
public void sort()
{
int size = 1;
int from = 0;
int to = a.length - 1;
while (size < to - from)
{
int offset = 0;
while(offset < to)
{
merge(from, to, offset);
offset = offset + (2 * size);
}
}
size = 2 * size;
}
public void merge(int from, int mid, int to)
{
System.out.println("Merging " + from + "..." + mid
+ " and " + (mid + 1) + "..." + to);
}
}
And ...
import java.util.Arrays;
public class MergeSortDemo
{
public static void main(String[] args)
{
String[] array = new String[]{"Jenny","Rob","Dereck","Mike","Dan"};
System.out.println(Arrays.toString(array));
MergeSorter sorter = new MergeSorter(array);
sorter.sort();
System.out.println(Arrays.toString(array));
}
}