Anyone who operates their own GSM network typically needs to program
and issue their own SIM cards — the alternative approach of letting
alien SIMs onto your network in guest roaming
mode with authentication
and ciphering disabled is generally unattractive.
And if you are a small community or lab operator, issuing your own SIMs
practically means being able to obtain (buy in small quantity) what are
called programmable SIMs: cards that allow you to program your own identities
(IMSI, possibly ICCID too) and keys (Ki and A3+A8 algorithm selection)
via some documented mechanism, typically using a special ADM PIN.
We are not the first vendor to offer programmable SIM cards — far
from it.
The most famous and most popular (at least in the Osmocom community from
which we offshoot) brand of programmable SIM cards are those sold by
Sysmocom in their webshop — and we (FreeCalypso) used them too
before we had our own.
However, these most common varieties of programmable SIM cards
(Sysmocom and other vendors we heard of over the years) are oriented
toward modern
users: those who operate newer G
networks
beyond pure GSM,
and those who are going to insert their SIMs into modern
phones.
From the perspective of someone who operates a pure GSM/2G network
for the sole purpose of providing service to vintage mobile phones,
these modern taste
programmable SIMs are rather unpleasant:
All
modern
programmable SIMs, from both Sysmocom and other vendors we heard of, are made in triple-cut physical form factor, i.e., the only fully solid form factor is 4FF (nano), with 3FF (micro) and 2FF (classic) provided in the form of additional plastic shells around that 4FF piece. However, when you move that SIM around a lot between different sockets, and even during initial breakout from the ID-1 carrier, those 2FF and 3FF shells keep separating from the 4FF inner piece, making the whole structure very weak.Current Sysmocom SIMs (and the same situation likely holds for other vendors) are not pure GSM 11.11 SIMs, instead they are UICC-native cards with USIM and ISIM applications, plus a GSM 11.11 SIM application only for backward compatbility. From the viewpoint of a pure GSM network operator, having to understand and program all those ADF.USIM and ADF.ISIM files creates a significant additional cognitive load that is totally undesired — or you can leave them unprogrammed and then end up in troubleshooting nightmare land if the phone you inserted the SIM into does understand those USIM and ISIM files, and is trying to do something with them that you don't even understand.
Fortunately, we as in FreeCalypso were able to find an older programmable SIM card model that is GSM 11.11 SIM only, without USIM or ISIM applications (and furthermore, no UICC at all!), these cards were still freely orderable at least as of 2021 (when we got our batch), and we were able to get them made for us in a 2FF-only cut, meaning that the 2FF piece is fully solid!
The card model we got is one that was previously used and sold by Sysmocom (apparently some time around 2013), known in the Osmocom community as GrcardSIM2, made by Grcard in China. We got a new batch of these cards made for us in 2021, in a 2FF-only cut with our own color scheme and with FreeCalypso artwork on the plastic, and our version is called FreeCalypso Community SIM, model FCSIM1. We opted to not provide any programming data to Grcard factory at the time of batch production, instead our model is that every downstream user needs to program their own card(s) as needed for their unique environment using our fc-simtool utility, which is the official programming tool for FCSIM1.