Bad Padding exception when trying to decrypt the file

Question

Hi i am trying to decypt a file in java which is encrypted in c++ but i get the pad padding exception
javax.crypto.BadPaddingException: Given final block not properly padded
     at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
     at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
public byte[] decrypt(byte[] str) {
try {
// Decrypt
     System.out.println("beforedecrypt-->"+str.length);
     byte[] input = new byte[64];
          while(true) {
                    int bytesRead = fin.read(input);
                    if (bytesRead == -1) break;
                    byte[] output = dcipher.update(input, 0, bytesRead);
               byte[] output = dcipher.doFinal();
     // byte[] utf8 = dcipher.doFinal(str);
     System.out.println("afterdecrypt-->");
// Decode using utf-8
return output;
} catch (javax.crypto.BadPaddingException e) {e.printStackTrace();}
catch (IllegalBlockSizeException e) {e.printStackTrace();}
catch (Exception e){e.printStackTrace();}
return null;
}

Answer 1

MuppidiJava wrote:
Sorry man..i got the same key in java..which you got i followed everything was mentioned... but i did not get the same key using C++ But did you compensate in your Java for the C++ bug I highlighted involving the creation of the bytes from the password? I bet you didn't. Did you even talk to your C++ guys about the bug? I bet you didn't.
as i said i was not good at it..but your sample cpp code would have fixed it easily. Did you look at the Microsoft Crypto documentation? I bet you didn't. Did you try to learn enough C++ to add in the few lines of code needed to export and print out the generated key? I bet you didn't. Did you try to get the C++ guys to help you on this?
I runing short of timeSorry but your time management problem is your problem.
..thanks for your support..The BadPaddingException problem you have is almost certainly as a result of you not generating the same key bytes in your Java as are being generated by the C++. Since you get the same bytes as I do when not compensating for the C++ bug it is almost certain that the C++ bug is the root cause of your problem. If I compensate for the C++ bug I get a match between my C++ key bytes and my Java key bytes. If you don't spend effort in understanding the C++ bug and how to correct for it in your Java you are stuffed. If you don't spend time learning enough C++ to be able to export the C++ key then you will have great difficulty in proving that you C++ key bytes actually match your Java key bytes. I have explained what the bug is - the Java code to compensate for the bug is actually trivial. I have explained how to export the C++ key - the C++ code for this is small and straightforward. I'm not going to provide the C++ code nor the Java compensation code. This is a 'forum' and not a programming service.
P.S. You still have a problem with the '.' key on your keyboard.