md5 - sellos - solucion factible ejemplos

¿Cómo revertir MD5 para obtener la cadena original?

Question

Posible duplicado:
¿Es posible descifrar hash md5?

¿Es posible obtener una cadena de MD5 en Java?

En primer lugar, una cadena se convierte en suma de comprobación MD5. ¿Es posible volver a colocar esta suma de comprobación MD5 en el texto original?

Supongo que utiliza MessageDigest, cualquier ayuda es muy apreciada, incluso otras bibliotecas de Java.

Solo quiero señalar si no es posible cómo puede esta aplicación: https://play.google.com/store/apps/details?id=com.fab.md5&hl=en

Incluso convertí algo de texto a la suma de comprobación MD5 utilizando otra aplicación y usé esta suma de comprobación para ver si la aplicación podía convertirla de nuevo a texto y así fue.

Answer 1

No es posible que eso sea todo el punto de hash. Sin embargo, puede utilizar la fuerza bruta recorriendo todas las posibilidades (utilizando todos los caracteres de dígitos posibles en cada orden posible) y mezclándolos y verificando una colisión.

Para obtener más información sobre hashing y MD5, etc., visite: MD5 , http://en.wikipedia.org/wiki/Hash_function , http://en.wikipedia.org/wiki/Cryptographic_hash_function y http://onin.com/hhh/hhhexpl.html

Yo mismo creé mi propia aplicación para hacer esto, su código abierto puede consultar el enlace: http://sourceforge.net/projects/jpassrecovery/ y, por supuesto, la fuente. Aquí está la fuente para un fácil acceso, tiene una implementación básica en los comentarios:

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);
}
}

Lo usarías como:

 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());

Answer 2

No, eso no es realmente posible, como

• Puede haber más de una cadena dando el mismo MD5
• Fue diseñado para ser difícil de "revertir"

El objetivo del MD5 y su familia de funciones de hash es

• para obtener "extractos" cortos de cadena larga
• para que sea difícil adivinar de dónde vienen
• para dificultar la búsqueda de colisiones, es decir, otras palabras que tienen el mismo hash (que es una exigencia muy similar a la del segundo)

Piensa que puedes obtener el MD5 de cualquier cuerda, incluso muy larga. Y el MD5 solo tiene 16 bytes de largo (32 si lo escribes en hexa para almacenarlo o distribuirlo más fácilmente). Si pudieras revertirlos, tendrías un esquema de compactación mágica.

Dicho esto, ya que no se utilizan tantas cadenas cortas (contraseñas ...) en el mundo, puede probarlas desde un diccionario (que se denomina "ataque de fuerza bruta") o incluso buscar en Google su MD5. Si la palabra es común y no estaba salada, tiene una posibilidad razonable de tener éxito ...