Hi Domi, I have attached another trace containing the following: - Location Update + Authentication of the MS that will send the SMS (packets 1-45) - Sending and receiving an SMS (text: “a5/1”) with encryption set to A5/1 (packets 46-140) - works - Sending an SMS (text: “a5/3”) with encryption set to A5/3 (packets 141-730) - the MS tries to send several times until it gives up. No Ciphering Mode Complete is received. - Switching back to A5/1 and resending the SMS with text "a5/3" (packets 731-827) - works I hope that helps. Thanks, Jan

Hi Neels, to switch to A5/3 on-the-fly, but just for curiosity, you could try to detach and re-attach the phone after switching to A5/3. I just tested that. It does not change the behavior. As soon as I switch to A5/3 the BTS never receives a Ciphering Mode Complete, after having sent the Ciphering Mode Command for A5/3 to the MS. This happens for SMS as well as the whole Location Update/Authentication/TMSI-Relocation procedure. Trying to attach the MS after enabling A5/3, the MS is not able to attach successfully and continuously tries to attach until it gives up. Similar to how it keeps trying to send an SMS with A5/3 enabled. I have attached another trace of the attach and detach with A5/0 (works), then A5/1 (works) and finally A5/3 (fails, tried several times). For the A5/3 attach, there is no Authentication Request/Reply. But also in cases where the Authentication is performed the following A5/3 ciphering fails in the same way. use osmo-bsc + osmo-msc + osmo-hlr instead? See: https://osmocom.org/projects/cellular-infrastructure/wiki/Osmocom_Network_In _The_Box I will try to test that setup and let you know if it helps. stable? So it's not your SDR coincidentally clock-unsyncing in the wrong moment by coincidence? I tested it many times, switching between A5/3,1 and 0 and using different phones. A5/1 (and 0 of course) works every single time. A5/3 did not work a single time. I'd say it's safe to assume that it's not the SDR failing in some way. Jan

Hi, I migrated my setup to the new Network In The Box configuration with separated components (from latest, not nightly). I tested whether the described issue with A5/3 is resolved, but it still does not work. Though, the behavior has changed. In the old setup a Ciphering Mode Command for A5/3 was sent, but a Ciphering Mode Complete was never received. Probably, what was happening is the following: In the new setup not even the Ciphering Mode Command is sent to the MS. Instead the BSC sends a Cipher Mode Reject to the MSC, if I am reading the logs correctly: <000a> a_iface_bssap.c:629 Rx MSC DT1 BSSMAP CIPHER MODE REJECT <000a> a_iface_bssap.c:453 BSC sends cipher mode reject (conn_id=65) <000a> a_iface_bssap.c:457 Cause code is missing -- discarding message! <0027> sms_queue.c:156 Sending SMS 13 failed 0 times. The full log is attached to the issue [1]. I am setting the encryption to A5/3 in both the MSC and the BSC. A5/1 continues to work without any problems. Thanks, Jan [1] https://osmocom.org/issues/3043