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I was reading https://reverseengineering.stackexchange.com/questions/15011/how-does-a-sim-card-work and from that, I can say that, really really simply put, a SIM card is sort of an extra memory that allow the phone to hold data that the carrier can use to communicate with.

Now let say the carrier deactivate a SIM (for instance a SIM that was not used for a REALLY long time). I'm asking myself what could be done with that SIM. Sure IMEI for instance in written inside the SIM. But it is not mapped to any carrier phone number anymore. The carrier only know of the existence of the SIM at this point, not its activity.

So what can be done with the SIM to make it work without having to reactivate it from the carrier for instance ? Or what other activities (programming wise) can be performed with the SIM at this point that for instance can make it work with a different carrier, sort of making it a stealth SIM on any carrier ?

I'm not asking for implementation details.... I'm just wondering if at all possible.

For instance when you buy a PC, if you Windows licence does not fit you purpose, you can flush the HDD and install a new OS, Windows, Linux, etc...

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  • \$\begingroup\$ A smart card (SIM/Bank card/...) is not just an extra memory, like a USB flash drive. There is a reason it is called "smart". It's because it only allows the outside world to access its data if the card is OK with that. Which typically means that in order to read/write/use parts of the data, you need to authenticate, either with PINs or cryptographic keys. So unless the carrier did something really dumb, there is no way you can use a SIM card in an unauthorized way. If it was possible, believe me, the phone companies would have gone bankrupt. \$\endgroup\$ – dim Sep 21 '18 at 11:36
  • \$\begingroup\$ @dim ;-) point noted. Thx Dim \$\endgroup\$ – snorlax Sep 21 '18 at 14:30
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The SIM card contains the IMSI (International Mobile Subscriber Identity) number and the associated private key. The IMEI (International Mobile Equipment Identity) is part of the phone.

Basically, the IMSI is the user name, and the private key is used similar to a password here. You can reuse that SIM card only when you find an operator willing to accept your account data.

Commercial operators just give you a new SIM card, as it is way cheaper to give you an envelope than to read the IMSI off your card and reactivate it.

What you can still do is read (and write) the phone book and SMS store on the card.

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  • \$\begingroup\$ 250 to 500 contacts sound like reasonable storage to consider for DIY projects. The question, however, whether or not that memory can be accessed on the deactivated card, potentially without knowing old user's PIN. \$\endgroup\$ – Maple Sep 21 '18 at 11:15
  • \$\begingroup\$ I know my old PIN number.... His answer helped me clarify my idea. Can I connect to a windows network without windows OS ? Yes. Can I use specific Windows features without OS ? It depends but mostly no. Therefore, can I do something with IMSI, IMEI and private key to access differents operators network and seem to be registered ? It seems answer is no... Right ? \$\endgroup\$ – snorlax Sep 21 '18 at 11:26
  • \$\begingroup\$ @snorlax, pretty much so. \$\endgroup\$ – Simon Richter Sep 21 '18 at 11:35
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    \$\begingroup\$ @Maple, the phone book and SMS store can only be accessed after entering the PIN. \$\endgroup\$ – Simon Richter Sep 21 '18 at 11:38
  • \$\begingroup\$ You could use the IMSI as a unique identifier for some kind of private project, although I'm not sure what. You could even use it with your own mobile network, although that's a lot of work: hackaday.com/2016/04/08/… \$\endgroup\$ – pjc50 Sep 21 '18 at 11:55

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