I presume that the main reason phone operators require a SIM card to get access
ID: 655778 • Letter: I
Question
I presume that the main reason phone operators require a SIM card to get access to the network is due to security and/or authentication purposes.
Just wondering why this is? What does a SIM card do that a phone can't? I imagine a SIM card is just data storage right for either some data or some algorithm that generates some data. And at the end of the day, you're just sending the network the right data to authenticate to them you are the owner of the account. Why can't this data just be generated and sent from an app on the phone?
Wouldn't it make more sense? Phone makers won't need to put in a SIM card slot, and phone networks suddenly become much more accessible because users don't need to organize to have a physical thing sent to them for every device they want connected to the network.
Explanation / Answer
The SIM card, initially, is the root for the legal value. The operator wants to bill the user, and does not want users refusing to pay and claiming that they did not made these three-hours calls to Tanzania. Within the legal context of European countries, where GSM was designed, the SIM card was convenient: it could serve as a basis for legal proofs, under the idea that the SIM card cannot be cloned, and thus if the secret key contained in the SIM card was used then the actual card was used, and the owner could then be formally held responsible for the calls, and pay for it (and three hours to Tanzania imply a non-negligible amount of money).
It is plausible that the SIM card concept was pushed by some French lobbying, the "smart card" being a French speciality (and, at that time, was still patented by some French companies).
Another facet of the issue is that in Europe, you can unlock your phone. Operators are legally mandated to send phone owners an "unlock" code, no more than six months after buying the phone, so that users may then reuse the same hardware phone with another operator. There again, the SIM card is convenient. Compare with SIM-less phones in North America: there is no SIM, but the phone is hardwired (through its firmware) to a specific operator, and you cannot easily (or at all) repurpose the phone to another operator.
The SIM card thus incarnates the separation between the phone hardware and the contract with the operator.
So the "why ?" is, as usual, mostly a matter of History; GSM phones need a SIM card because GSM phones have always needed a SIM card. Yet there are at least semi-rational reasons why GSM phones have SIM cards, and SIM-less phones are not necessarily "better" than phones with SIM.