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What kind of data can be stored on sim cards and reactivated on another device?

Is it safer to store data on the device or the sim card?

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  • I.e. Details of a user's contacts
    – KimberleyK
    Commented Nov 9, 2015 at 3:03
  • I assume that you generally leave the SIM card in the phone? If you frequently remove it then physical security will be the biggest concern.
    – Neil Smithline
    Commented Nov 9, 2015 at 3:37
  • I am concerned someone might steal the sim card from the device and use it in their own device to portray data. It is easier to sneak out of an office with someone's simcard than it is with someone's phone / tablet. A person may not even realise something is wrong until they attempt to use the device.
    – KimberleyK
    Commented Nov 9, 2015 at 5:44
  • If someone is fiddling with a phone or tablet to remove a SIM card, I would at least be curious what they are up to... In comparison, grabbing a phone from someone's desk and dropping it in a pocket can be done in a second or two.
    – user
    Commented Nov 9, 2015 at 13:55
  • 1) 12pm midday. Someone steals the device. Victim realises straight away and calls telephone provider to cancel contract and prevent any unauthorised calls. 2) 12pm midday. Someone steals the sim card from a device. Victim does not realise until they try to use their phone ( this could be days! ). User exploits data on the device and uses the sim card to make a number of unauthorised calls.
    – KimberleyK
    Commented Nov 9, 2015 at 22:47

3 Answers 3

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The standard user-accessible data are call history, SMS and contacts, if your phone is set to store these on the SIM. Most smartphones store these in the phone by default (as most SIMs have very limited storage space).

In addition, there could be STK applications that store proprietary data on the SIM. Very few people use these any more and the data stored is probably only relevant to the carrier.

If you want to protect the data on the SIM, simply set a SIM Pin (note this is different from your phone's unlock PIN). The chip in the SIM will not allow any data to be accessed without the PIN. Alternatively, set your phone not to store anything on the SIM and encrypt your phone with a password.

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The SIM card contains number of data items :

  1. Items which are related to the network operations which can be triggered by basic operations of the phone - Kc (encryption key), IMSI (the card id in the network), MSISDN (the phone number - not always).
  2. Items which are related to the network operations which can't be read - Ki (the main key of the card - the Kc derived from it).
  3. Items for basic information - ICCID (the card id - like a MAC address), location info (the info of the last connected BTS).
  4. Numbers and SMS - remember that old phones saved the SMS and the phonebook in the SIM card? Apparently new phones can store as well. In addition, the SIM contains some "operator's" and default numbers like emergency numbers.

There are a lot of data in this tiny card - ETSI TS 11.11

For the second question - It's more secure to store data in the SIM card, as "only" the operator can reach the data inside. It like a safe (SIM card) inside a "locked" room (android or ios or whatever).

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One surprising piece of information retained by the SIM is the Kc encryption key. This is the session key the phone last used in the current cell. If you could capture a call over the air and read the Kc from the SIM then it is trivial to decrypt the recorded call.

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