On Tue, Mar 16, 2010 at 12:07 PM, Dieter Spaar spaar@mirider.augusta.dewrote:
Hello Sebastien,
On Tue, 16 Mar 2010 10:04:07 +0100, "=?UTF-8?Q?S=C3=A9bastien_Lorquet?=" < squalyl@gmail.com> wrote:
I know that smart card EEPROMS are rated for 100k writes, but I would not rely on that. In fact, this depends on how often is the EF.Kc file
written,
which was my original question. Every 30 seconds or every day? Every day
is
of course OK.
It is only written if an AUTHENTICATION REQUEST from the network is performed. This usually happens when the phone is turned on and does a location update. The network can also perform an AUTHENTICATION REQUEST when doing a call or similar things, however usually this is not done every time and the previous Kc stored on the SIM is reused as Sylvain explained it. For OpenBSC and OpenBTS the default is that there is no AUTHENTICATION REQUEST at all, so no Kc is written (I am not 100% sure if this is true for OpenBTS, but I guess so).
Additionally, how often are these other files written (LOCI, BCCH) ?
They are written when a location update is done or the cell changes. However it depends on the phone if the data is really written to the SIM every time, sometimes the phone caches those data and writes them to the SIM only when the phone is turned off. For OpenBSC and OpenBTS writing should not happen that often because there is usually only one cell with fixed parameters. And I guess you will probably not actually write to the EEPROM if the same data is already stored (or a least the Card OS should do it this way).
OK, I will neglect this part for the moment and implement them as regular files. If it happens that the update rate is really a danger for the card eeprom, I'll implement a log structured file type.
SmartCardFocus has a ID0 cutting service, that can turn any card into a SIM
sized module:
This is the best option I know so far.
Thanks, I did not know that. It would be interesting to know what tool
they use and if it is available for a reasonable price.
Seems to be 1.20 EUR per card. Two options: either they may have a small punching tool, and do that by themselves, or they may have a subcontractor with a big laser cutter or a CNC or something else... There were impressive machines at the Cartes Salon, I would not be surprised if they had a supplier with a monster to do that.
Sebastien