On my Samsung Galaxy SIII, one can go to Settings -> More -> Security -> SIM card lock -> Set up SIM card lock -> Change SIM PIN to change the default PIN that came with the SIM card. But what about the PUK (the 8-digit number that comes with the SIM card to unlock the card after 3 failed 4-digit PIN number attempts)? Can the PUK also be changed from within the Android GUI, or is it a fixed number stored on the SIM card which cannot be changed?


3 Answers 3


The PUC (PUK) is a SIM-specific code assigned by the service provider. - Personal Unblocking Code (Wikipedia)

That means you cannot change it with help of your android device.

If you want to crack it you must watch this video

Video is about 'Rooting The Sim' by Karsten Nohl at BlackHat 2013.

In this video Nohl showed vulnerability that almost every sim have which was manufactured before 2013(Also Some cards after that whoes providers have not fixed this security hole)

Procedure -Send binary sms with OTA command to card requesting response

-Crack DES signing key that sign Java virus and sent through binary sms

-Leverage gaps in Java VM memory separation to access arbitrary sim card data

Results -Card may response with DES signed error message

-Card install and execute signed Java applet

-Malicious applet extract ki,banking applet etc. and send ti attacker via sms

Once an attacker cracks the key, he can commit premium SMS fraud, circumvent caller-ID checks, manipulate voice-mails, redirect incoming calls and text messages, abuse USSD payments, track and phish users, install malware on their devices, or perform any other browser-based attack. With data access enabled, Nohl claims an attacker can clone SIM cards, decrypt 2G, 3G, and 4G traffic, clone NFC takers and future SIM applications, and alter the operating system to prevent future patching.

Nohl also claims to have been able to break out of the SIMs Java sandbox and get access to this personal unblocking key

  • I guess it's a read-only piece of information on the SIM card. Dec 15, 2014 at 18:23
  • 1
    Yes. They both are synonymous. If you want to change it you have to contact your service provider and ask for PUK. If you can prove that you are owner of sim they can give you the PUK.
    – Ash Ishh
    Dec 16, 2014 at 5:26
  • 1
    In this talk (@22:40) he mentioned that binary sms can also be sent through some phones (he used specific reprogrammed motorola device)
    – Ash Ishh
    Dec 18, 2014 at 12:36
  • 1
    Yeah, I've seen that, the Motorola device he had must be something wonderful for hackers to have to experiment with. Anyways, I thought putting the device in Airplane Mode would cut off all communication to the device, including binary SMS messages sent by the network operator, but what the speaker in the talk said is true, this is not the case. I guess I will be turning my phone completely off while in airplanes from now on. Thanks. Dec 19, 2014 at 11:44
  • 1
    As a minor update, I would like to add that upon logging in to the network operator's website with my phone number and password I was also able to view my PUK on such website. Dec 20, 2014 at 21:24

I realize this is an older thread, but to provide useful into to others reading the page now I thought I'd still reply.

This doesn't always work with every phone, but if it doesn't work it wouldn't cause any harm. It also requires that you know what the current PUK number is. This can often be found on the credit card size card that your SIM card came attached to (if you still have it) or it can usually be obtained from your wireless provider fairly easily so long as you can verify that it is your account.

All you have to do is dial this code into your phone replacing "old PUK" with the PUK provided by your wireless provider, and "new PUK" with any 8-digit code of your choosing. Note you don't use any spaces when you enter the code.

** 05 * old PUK * new PUK * new PUK #

  • I believe this answer is misleading. It should be "new PIN" rather than "new PUK". Hence that dial code is used for changing PIN instead of changing PUK. Jun 15, 2020 at 9:15

You should write new pin new pin, there is no way to change puk code. Your topic explains how to make blocked pin code active.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .