Question/Idea about the Sim Card

I am a programmer, but have never messed with unlocking phones. My question however is this.

If you take a IPhone sim card, and put it in an unlocked or AT&T locked phone, it works. but going the other way does not.

So at some level the sim cards are identical. Is it possible that a simple header is being written with a common number? because one iphone card works in another without a problem.

I do not have a SIM Card reader, but If it is as simple as a header, can someone try and read an iphone SIM, and then a regular SIM, and post the header changes? also if you clone an iPhone sim it works.

I guess what I am saying is that if it is a simple header change, then you could do that change to a T-Mobile, or other SIM card, and see if it now works.

Just my $.02 cents and I wish that i had a SIM card reader to try it myself.

If this idea worked, along with the free activation now, then we would be set.

i am thinking along the same line too, cstxmedic82

i am getting a sim reader/writer, hopefully we could "trick" the iphone that the AT&T sim is being used...

First a SIM reader is usually limited to phone book and SMS entries so unless you have special software adapted to your reader your unlikely to be able to do anything to the SIM card. Second - if it was that easy I think people would be doing that rather than (in the xda-developers forums at least) developing a sim unlock tool for each and every htc phone released.

Not trying to put you off - I'm just putting the realistic point of view up.

The difference here, is that if I have t-mobile, and I take a t-mobile sim card from a wing, and put it in a razr, it works, so the phone is simply locked to the carrier. However, with an iphone, if you take another AT&T sim, and put it in the IPHONE, it does not work, you cannot make calls. So that is why I believe that the lock is that the phone is looking for something special in the SIM card. Also, since this phone has NO carrier branding, it is not like HTC selling the phones and the carriers customizing the updates, OS, etc...

All updates come straight from apple, and would it not be easier to simply look for a specific SIM header/code, rather than apple compiling and releasing an update for CINGULAR, and then whoever gets the phone in europe, VODAFONE, T-Mobile, etc...

I just think that maybe we are overthinking this, and it could be that simple. I think apple thought they had everyone with ITunes activation, so the sim thing did not need to be that comnplicated. Now that DVDJon has broken that, it might be just "that simple"

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Originally Posted by cstxmedic82

I am a programmer, but have never messed with unlocking phones. My question however is this.

If you take a IPhone sim card, and put it in an unlocked or AT&T locked phone, it works. but going the other way does not.

So at some level the sim cards are identical. Is it possible that a simple header is being written with a common number? because one iphone card works in another without a problem.

I do not have a SIM Card reader, but If it is as simple as a header, can someone try and read an iphone SIM, and then a regular SIM, and post the header changes? also if you clone an iPhone sim it works.

I guess what I am saying is that if it is a simple header change, then you could do that change to a T-Mobile, or other SIM card, and see if it now works.

Just my $.02 cents and I wish that i had a SIM card reader to try it myself.

If this idea worked, along with the free activation now, then we would be set.

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good thinking, but unfortunately it is not that simple... the actual sim card is really a small microprocessor with memory as opposed to a simple storage device. the card itself has a file system with a whole slew of files that tell the phone everything from what network it is supposed to use to how to identify itself to innocuous things like what number to call for SMS service. besides this the microprocessor on the sim card has the ability to send and receive data in encrypted form. the real trick is to determine what data is being used by the phone to determine when to allow a sim as valid and when not to.

the majority of manufacturers use similar methods for their phones but with the iphone it could really be a number of different ways: it could be something as simple as the iphone only accepts sim cards with an identifier (ICCID) that is within a certain range. we just dont know yet...

fortunately i do have a sim reader... :) quite a few actually...

The history of unlocking phones has shown that the unlock code is generated based on the IMEI number and the actual phone number. This has been the case for all of Nokia's phones and most others.

Hi
A few years ago I did a program for a i-cafe to read/write smart cards. When we bought the smart card readers we also saw on sale some SIM card readers/writers from the same company ( www.towitoko.de ).
Just my 2 cents

i guess if the phone works on one sim only and not any other AT&T sim this means that the sim provides a 'unique' code or instruction or signal to the phone and the itunes server to proceed...any comments?

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Originally Posted by rob13572468

good thinking, but unfortunately it is not that simple... the actual sim card is really a small microprocessor with memory as opposed to a simple storage device. the card itself has a file system with a whole slew of files that tell the phone everything from what network it is supposed to use to how to identify itself to innocuous things like what number to call for SMS service. besides this the microprocessor on the sim card has the ability to send and receive data in encrypted form. the real trick is to determine what data is being used by the phone to determine when to allow a sim as valid and when not to.

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Do you have a link to any reading material that discusses a SIM being a micro processor? I always though it was simple storage and that's all.

I've got a lot of SIMs and have never seen a CPU on any of them. My understanding (and every source I've read on it) is that it stores data and that's all, it doesn't manipulate or receive information. Thanks.

Quote:

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Originally Posted by exNavy

Do you have a link to any reading material that discusses a SIM being a micro processor? I always though it was simple storage and that's all.

I've got a lot of SIMs and have never seen a CPU on any of them. My understanding (and every source I've read on it) is that it stores data and that's all, it doesn't manipulate or receive information. Thanks.

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http://www.gsmworld.com/using/algorithms/index.shtml

http://www.environmental-studies.de/.../sim-card.html

especially this one:

http://www.gemplus.com/techno/sim/


the microprocessor on a sim card is abstracted form the user... you dont know that its there as the reared program (a la cardinal) just shows you files and a file system. in reality the microprocessor is in the background sitting between the reader and the internal card memory acting as arbitrator and deciding which data is allowed to be released for a given privelege level. additionally the processor handles all the crypto operations for data that cannot be sent out of the card in plaintext.

but this is elementary.. all of this is detailed in the gsm standard.