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I have an old cell phone that I forgot the password to. You can have unlimited tries to unlock the phone. It has the basic 0-9 input system with 4 characters unlocking the phone. I was wondering if there would be any way I could brute force attack this?

I have the Samsung Instinct and the chord to connect from the phone to the PC.

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closed as off-topic by Tom Wijsman, CharlieRB, Daniel Beck Aug 23 '13 at 19:42

  • This question does not appear to be about computer software or computer hardware within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

This question appears to be off-topic because it is about an electronic device for which there is no way to do it through the interface that connects to the computer. – Tom Wijsman Aug 23 '13 at 19:14
up vote 0 down vote accepted

I suggest you first sit down and think about what passwords you might have chosen:

  • PINs you use elsewhere
  • Any significant 4-digit number you can think of, like important years in your life
  • Did you maybe map a 4 character word to 4 digits?

Then write out variations on them, like reversing or changing one digit.

First you try these.

Then you 'walk across' the keypad in patterns, like all 2x2 blocks with 4 starting points in two directions. Don't forget 2580 and 0852 ;-)

Then you do a Google search for analyses on what PIN codes people often use and try those.

Only after that do you start the brute force.

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Well, by definition, a brute force attack would mean to try out all possible passwords.

You have unlimited tries, so that's a great start. Only numbers (0-9) are allowed, and a fixed length of 4 characters? That's excellent. Now you only need 10,000 tries.

While this is an extremely easy password, it is unfortunately on an old device, so you could not automate the cracking process.

You will need to manually try passwords like so: 0000, 0001, 0002, 0003, ... until the password is accepted.

In the worst case, it will take you 10,000 tries.

Now, let's say it takes about 10 seconds to try one password because you need 3 seconds to enter the digits, and the phone says "wrong" and freezes for like 7 seconds or something. So that is 100,000 seconds to try all the possibilities, which is about 27 hours. You can perhaps split this task into 10 days, so each day you'll spend 10,000 (a little under 3 hours) seconds to try the password. It's probably a good idea to turn on some radio or watch some TV while trying in case you get really bored of it.

Good luck!

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So there is no way I can persay connect it to my computer and initiate a brute force attack? – Chase Ernst Aug 23 '13 at 18:59
Without knowing the exact model of the phone or anything like that, I would say, mostly no. However, if you do manage to connect it to a PC and could automate the "cracking", I'm sure you'd also be able to just reset the password from PC somehow. – user1032613 Aug 23 '13 at 19:01
I know the make and model. It is a Samsung Instinct, and I have the cord to connect to the PC. How would I go about trying to automate the cracking? – Chase Ernst Aug 23 '13 at 19:05
Sorry but I really don't think you could. Again, if you could, then you could probably also just erase the password altogether. The PIN punching robot is not bad if you think 27 hours of punching by yourself is a bit too much, although it might take more effort to build/acquire the robot, and it might longer than 27 hours. – user1032613 Aug 23 '13 at 19:08
Oh, well that is unfortunate. Well thank you for your help anyways! – Chase Ernst Aug 23 '13 at 19:09

You could build a PIN-punching robot, similar to this one demonstrated at Def Con.

It's highly unlikely, though not fundamentally impossible, to use your computer to crack the PIN. You don't mention which phone you have so there's no way to tell for sure.

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