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annotate doc/Formatting-thoughts @ 93:6041c601304d

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fcsim1-mkprov: revert OTA key addition It appears that GrcardSIM2 cards (which is what we got for FCSIM1) do not support OTA after all, contrary to what we were previously led to believe by some tech support emails from Grcard - apparently those support emails and OTA descriptions referred to some other card model(s).
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 21 Apr 2021 05:38:39 +0000
parents 7c9a3130fb66
children
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1 Thoughts on card (re)formatting
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2 ===============================
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4 ETSI and 3GPP specs give many more degrees of freedom to SIM card issuers than
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5 just the content of various EFs: the card issuer gets to decide which DFs and
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6 EFs will be present vs. which ones won't be present at all, and for many EFs
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7 the size (allocated space) is variable per the specs and up to the card issuer.
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8 In the case of record-based EFs, both the record size and the number of records
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9 are often left up to card issuers to tune as desired.
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11 In the Mother's opinion, a truly programmable SIM would be one where every
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12 downstream owner of each card (not just the initial factory or the party putting
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13 up big bucks for a large custom production run) can do a full reformat: erase
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14 the file system and then create whatever tree of DFs and EFs she desires, with
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15 full control over each file's allocated size, structure and access conditions.
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17 The problem, however, is that the people who work with big bucks and who control
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18 SIM card manufacturing have taken away our community's ability to freely
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19 reformat our programmable SIMs downstream of the factory. To the best of our
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20 knowledge, there has only ever been one SIM card model in the entire history of
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21 Osmocom community that supported downstream reformatting, and this model was
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22 sysmoSIM-GR1:
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24 https://osmocom.org/projects/cellular-infrastructure/wiki/GrcardSIM
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26 But Grcard company no longer sells that original card model, and for their new
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27 card model (GrcardSIM2, branded sysmoSIM-GR2 or FCSIM1) there is no published
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28 documentation for how to erase the card file system and recreate it differently.
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29 We can only guess that this ability probably exists, but Grcard people are
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30 refusing to disclose the secret knowledge of how to do it unless we pay them
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31 some ginormous sum of money.
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33 The current offering from Sysmocom (sysmoISIM-SJA2) does not fare any better in
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Mychaela Falconia <falcon@freecalypso.org>
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34 this regard. These cards are natively UICC, and in the world of UICC there
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35 exist partially standardized commands for creating and deleting files, defined
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36 in ETSI TS 102 222. However, these commands are only partially standardized:
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37 the ETSI spec gives the general principles and the command structure, but many
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38 of the details as to exactly what needs to be put into the TLV structure fed to
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39 the CREATE FILE command in order for that command to succeed constitute
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40 proprietary knowledge. Our experiments with this CREATE FILE command on
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41 sysmoISIM-SJA2 were unsuccessful. The only way how the file structure of
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42 Sysmocom cards would become truly editable by end users would be if Sysmocom
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43 were to publish at least one fully worked-out example of a real CREATE FILE
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44 command that creates some dummy non-standard file just to prove it working,
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45 followed by a working example of a DELETE FILE command that deletes this newly
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46 created file, restoring the card to its original state. However, we reason that
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47 Sysmocom would probably be willing to do this support work only if someone paid
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48 them for it on an hourly support basis, or ordered a large custom batch of cards
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49 from them and required this support knowledge as part of that deal - and we
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50 (FreeCalypso) are not currently in a position to pursue either of those two
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51 routes.