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spec: ATT = 0

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Oliver Smith 2020-04-08 15:26:59 +02:00
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commit 18bf9bb185
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docs/imsi-pseudo-spec.adoc
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@ -359,7 +359,18 @@ and related branches for IMSI pseudonymization can be found at the above URL as
well.
== Recommendations for Real-World Implementations
=== ATT = 0
=== BCCH SI3: ATT = 0
When changing from one pseudonymous IMSI to the next, it is important that the
ME does not detach from the network. Otherwise it would be trivial for an
attacker to correlate the detach with the attach of the same ME with the next
pseudonymous IMSI.
This is controlled with the ATT flag in the SYSTEM INFORMATION TYPE 3 (SI3)
message on the Broadcast Control Channel (BCCH), see 3GPP TS 44.018 Section
10.5.2.11. It must be set to 0.
// FIXME: verify how it set with operators in germany (OS#4404)
=== End to End Encryption of SMS
[[warn-no-imsi-change]]
=== Warning the User if the IMSI Does Not Change