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  MD5 on same file gives different hash  (Read 899 times)
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Offline roland
« Posted 2012-01-02 08:33:08 »

Can someone tell me what is wrong with this code? Each time I use it on the same file, it gives a different hash code :/
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   public static byte[] generateHash(String file)
   {
      InputStream is;
      try
      {
         MessageDigest algorithm = MessageDigest.getInstance("MD5");
         algorithm.reset();
         is = new FileInputStream(file);
         is = new DigestInputStream(is, algorithm);
         is.close();
         return algorithm.digest();
      }
      catch (Exception e)
      {
         e.printStackTrace();
         return null;
      }
   }
Offline Riven
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« Reply #1 - Posted 2012-01-02 08:36:57 »

Where do you read the contents of the file?

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Offline roland
« Reply #2 - Posted 2012-01-02 08:59:23 »

hmm... you are right.
What about this? the same thing is still happening.

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   public static byte[] GenerateHash(String file)
   {
      InputStream is;
      try
      {
         MessageDigest algorithm = MessageDigest.getInstance("MD5");
         algorithm.reset();
         is = new FileInputStream(new File(file));
         
         byte[] bytes = new byte[1024];
         
          int read = 0;
          while ((read = is.read(bytes)) != -1) {
             algorithm.update(bytes, 0, read);
          };
          is.close();
         
          byte[] digest = algorithm.digest();
         
         return digest;
      }
      catch (Exception e)
      {
         e.printStackTrace();
         return null;
      }
   }
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Offline roland
« Reply #3 - Posted 2012-01-02 09:04:58 »

Oops  Grin  the second version does work. I was printing out the hash wrong System.out.println(bytes) instead of System.out.println(new String(bytes))
Thanks Smiley
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