How to reverse MD5 to get the original string

Question

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 amp 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

User · Accepted Answer

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

User · Answer

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 lt String gt  characters   new ArrayList lt  gt         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                                                      amp                         -                                                                           lt                gt                        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  lt   maxLength  i                  possibilities     long  Math pow characters size    i                     return possibilities             public void addExtendedSet             for  char c    char  0  c  lt    char  31  c                  characters add String valueOf c                         public void addStandardCharacterSet             for  char c    char  32  c  lt    char  127  c                  characters add String valueOf c                         public void addLowerCaseLetters             for  char c    a   c  lt    z   c                  characters add String valueOf c                         public void addDigits             for  int c   0  c  lt   9  c                  characters add String valueOf c                         public void addUpperCaseLetters             for  char c    A   c  lt    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  gt  60                minutes    int   seconds   60               if  minutes   60  gt  seconds                    minutes   minutes - 1                             if  minutes  gt  60                    hours    int  minutes   60                  if  hours   60  gt  minutes                        hours   hours - 1                                               if  hours  gt  24                    days    int  hours   24                  if  days   24  gt  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  lt  arrayChars length  i                  characters remove arrayChars i                           if  characters size    lt  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  lt   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    lt  length                    for  int n   0  n  lt  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  amp  0xf0   gt  gt  4           int low    b  amp  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  lt  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  gt  gt  gt  8    table  crc   b   amp  0xff                      return Integer toHexString crc                                                                                                 Copyright  c  2009  2012 Mountainminds GmbH  amp  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          lt ul gt      lt li gt http   en wikipedia org wiki Cyclic redundancy check lt  li gt      lt li gt http   www geocities com SiliconValley Pines 8659 crc htm lt  li gt      lt  ul gt          private static final long POLY64REV   0xd800000000000000L       private static final long   LOOKUPTABLE       static           LOOKUPTABLE   new long 0x100           for  int i   0  i  lt  0x100  i                  long v   i              for  int j   0  j  lt  8  j                      if   v  amp  1     1                        v    v  gt  gt  gt  1    POLY64REV                    else                       v    v  gt  gt  gt  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  lt  data length  i                  final int lookupidx     int  sum   data i    amp  0xff              sum    sum  gt  gt  gt  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

[md5] How to reverse MD5 to get the original string?

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