Non-human readable file handling

Hi,

I want to store a password (which the user has chosen to login to my program) in an external file.
However i don't want the external file to be readable in anyway, e.g. when opening the file in windows notepad it should not display the password text. I have tried binary files (FileOutputStream and DataOutputStream classes), although the text editor can't read the file properly it still displays the password text i have written to it.

Is there any way in java i can save a password in an external file and be 100% sure that the password cannot be retrieved unless read by my program. I was thinking along the lines of just saving it using some sort of java class rather than having to write some sort of complex algorithm which i write the password with then read it back by reversing the algorithm (not sure if that would make sense to experts!) but i hope you get the idea of what im trying to do.

Thanks !
LVL 18
Ravi SinghSenior Software EngineerAsked:
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CEHJConnect With a Mentor Commented:
You can play with this: put it in a main method:

            String enteredPassword = args[0];
            java.security.MessageDigest md5 = java.security.MessageDigest.getInstance("MD5");
            // Just an example - all you'd be storing is 'digestedPassword' in a file
            String password = "abracadabra";
            byte[] digestedPassword = md5.digest(password.getBytes("UTF8"));
            byte[] enteredPasswordDigested = md5.digest(enteredPassword.getBytes("UTF8"));
            System.out.println(new sun.misc.HexDumpEncoder().encode(digestedPassword));
            System.out.println(new sun.misc.HexDumpEncoder().encode(enteredPasswordDigested));
            System.out.println(md5.isEqual(enteredPasswordDigested, digestedPassword)? "You're in!" : "No dice!");
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CEHJCommented:
You should store the password in the file as an MD5 hash and then compare that to the MD5 hashed value of the input. The MD5 hash is unreadable and 'uncrackable'
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Ravi SinghSenior Software EngineerAuthor Commented:
Hi CEHJ where can I learn more about MD5? Is there any online tutorials? Thanks!
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CEHJCommented:
See

http://javaalmanac.com/egs/java.security/Digest.html

You can write the byte buffer into the file
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CEHJCommented:
8-)
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