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imsi-pseudo
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spec: SIM applet: verify: next IMSI is different 

Suggested by ROS, so it would not be possible for the HLR to send the
same pseudonymous IMSI with an increased counter.

Seems like a good idea to me, if there was a bug in the HLR and it would
send the same pseudo IMSI for that reason, the SIM would not reset the
imsi_pseudo_lu counter.
This commit is contained in:
Oliver Smith 2020-05-08 08:54:27 +02:00
parent 29a79afacc
commit 04ff01ef63
1 changed files with 4 additions and 2 deletions
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6
docs/imsi-pseudo-spec.adoc
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@ -280,8 +280,10 @@ The SIM applet registers to a suitable SMS trigger (3GPP TS 43.019, Section
6.2). When an SMS from the HLR/HSS in the structure of <<sms-structure>> arrives,
the applet must verify that the SMS is not outdated by comparing `imsi_pseudo_i`
from the SMS with the last `imsi_pseudo_i` that was used when changing the IMSI
(initially 1 as in <<hlr-imsi-pseudo-i>>). The new value must be higher,
otherwise the SMS should not be processed further.
(initially 1 as in <<hlr-imsi-pseudo-i>>). The new value must be higher. The
SIM applet must also verify, that the pseudonymous IMSI arriving in the SMS is
different from the currently active IMSI. If any of the checks fail, the SMS
must not be processed further.
The SIM applet registers a timer with `min_sleep_time` from the SMS. When the
timer triggers, EF~IMSI~ of the SIM/USIM is overwritten with the new pseudonymous