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docs/spec: SMS structure

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Oliver Smith 2020-04-08 10:33:52 +02:00
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docs/imsi-pseudo-spec.adoc
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@ -174,9 +174,9 @@ the next pseudonymous IMSI arrives from the HLR. A reference implementation is
provided in <<reference-src>>.
The SIM applet registers to a suitable SMS trigger (3GPP TS 03.19, Section
6.2). When an SMS from the HLR in the format of <<sms-format>> 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applet must verify that the SMS is not outdated by comparing imsi_pseudo_i from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
6.2). When an SMS from the HLR 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the applet must verify that the SMS is not outdated by comparing imsi_pseudo_i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.
@ -280,12 +280,40 @@ An SMS is sent to the SMS - Service Centre (SMS-SC) with the newer pseudonymous
IMSI (higher imsi_pseudo_i, see <<hlr-imsi-pseudo-i>>) and related
imsi_pseudo_i value.
[[sms-format]]
==== SMS Format
[[sms-structure]]
==== Next Pseudonymous IMSI SMS Structure
* min_sleep_time
* imsi_pseudo
* imsi_pseudo_i
// FIXME
IMPORTANT: This is a draft. The structure is likely to change after the
reference implementation phase.
.Next pseudonymous IMSI SMS structure
[packetdiag]
----
{
colwidth = 32
0-31: IMSI_PSEUDO_I
32-63: MIN_SLEEP_TIME
64-119: IMSI_PSEUDO
120-127: PAD
}
----
IMSI_PSEUDO_I: 32 bits::
See <<hlr-imsi-pseudo-i>>.
MIN_SLEEP_TIME: 32 bits::
Amount of seconds, which the SIM applet should wait before changing to the new
pseudonymous IMSI. Since it is unclear when the SMS will arrive (ME might be
turned off), this is a minimum amount.
IMSI_PSEUDO: 60 bits::
Telephony Binary Coded Decimal (TBCD, 3GPP TS 29.002) version of the next
pseudonymous IMSI.
PAD: 8 bits::
Padding at the end, should be filled with 1111 as in the TBCD specification.
== Error Scenarios
=== Next Pseudonymous IMSI SMS is Lost