Password comparing in Android

Question

So I have stored password as hash in shared preferences, when user puts password I need to make a hash of it and compare with stored one.

Should it be done in AsyncTask or Thread because calculation and comparison could freeze UI? And then do you know a clean way to recieve result (true, false) from asynctask or thread?

public void startGenerateCode(View view) {
    String pinCompare = pin; //pin is class variable obtained from editText
    pinCompare = tools.bin2hex(tools.getHash(pinCompare)); 

    if(pinCompare.compareTo(session.getDetails("Pin"))==0){
        generateCode();
    }
    else
        Toast.makeText(this, "Wrong PIN", Toast.LENGTH_SHORT).show();

}

public void generateCode(){
    Intent i = new Intent(this, GeneratedCode.class);
    startActivity(i);
    overridePendingTransition(R.anim.right_slide_in, R.anim.right_slide_out);
    finish();
}

This is done in activity after button is pressed.

@android_jain so asyncTask is good for this? And can I start new activity in onPost ? When activity is killed earlier then comparison is finished then onPost could start next activity either? — Zolo, Feb 18 '17 at 12:10
you want to compare text stored in shared prefrence and comming from json — android_jain, Feb 18 '17 at 12:18
@android_jain No, comparing entered text transformed to hash with stored one. — Zolo, Feb 18 '17 at 12:30

JonZarate · Accepted Answer · 2017-02-18T12:40:24.877

2

Zolo,

I guess this process is triggered when someone presses a Button, such as login. I don't think you need any extra Thread to process the Hash calculus.

If you then have to connect to a server and send/receive data, then you should use it due to the asynchronous flow.

Response to comments on main post: Yes, you can start an Activity in onPostExecute.

Code example:

public void startGenerateCode(View view) {

    // Disable button         
    Button button = (Butto) view;
    button.setEnabled(false);

    String pinCompare = pin; //pin is class variable obtained from editText
    pinCompare = tools.bin2hex(tools.getHash(pinCompare)); 

    if(pinCompare.compareTo(session.getDetails("Pin"))==0){
        generateCode();
    } else {
        // If the login fails, re-enable the button to try again
        button.setEnabled(true);
        Toast.makeText(this, "Wrong PIN", Toast.LENGTH_SHORT).show();
    }
}

I did it by heart, so there may be mistakes.

edited Feb 18 '17 at 12:40

answered Feb 18 '17 at 12:11

JonZarate

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6
28

Yes, process is triggered after Button press. But I did it like this and once I tried app, and pressed button it started the comparison and new activity has not started I pressed it again and when I was pressing back button I had that activity twice in ActivityStack... I was not able to do it again, but it has happend. – Zolo Feb 18 '17 at 12:15
@Zolo That's another problem. If you want help on that, at least post your code. – JonZarate Feb 18 '17 at 12:17
1

@Zolo I think it's short. If the time it takes is less that 1 second, there is nothing to worry about. You can add some defensive programming, and disable the button after someone presses it so that there are no multiple activities launched. I edited my answer with the example. – JonZarate Feb 18 '17 at 12:37
@Zolo just added the example, check it out. – JonZarate Feb 18 '17 at 12:40

Password comparing in Android

1 Answers1