SDR# TETRA Demodulator Trunk Tracking Demonstration

[thewraith2008]

I found the follow quote in the standards in relation to the encryption of the SSI (element of the Layer 2 MAC) for encrypted PDUs.
The following would seem to indicate that the SSI is always encrypted for encrypted PDUs.

4.2.6 Encrypted Short Identity (ESI) mechanism

The ESI mechanism shall provide a means of protection of identities transmitted over the air interface. It operates in
addition to, or as a replacement for, the Alias Short Subscriber Identity (ASSI) mechanism described in ETSI
EN 300 392-1 [1], clause 7.

NOTE 1: In standard TETRA addressing no alias addresses are associated with a group address in the home system.
The ESI mechanism provides such an alias within a location area for all address types.

NOTE 2: The broadcast address as defined in ETSI EN 300 392-1 [1] is a reserved value of the group address so
ESI applies to it.

This clause describes a mechanism that allows the encryption of the SSI segment of addresses used by layer 2. The
event label and usage marker shall not be encrypted by this mechanism. USSI and SMI shall not be encrypted by this
mechanism. The mechanism is valid only for networks with air interface encryption applied. The mechanism shall be
integrated with the use of CCK within a location area in cells of security class 3, or with SCK for cells of security
class 2. Whenever encrypted signalling is used, the ESI shall be sent instead of the true identity. The mechanism uses
algorithm TA61 as shown in Figure 4.15.

xSSI are all short addresses valid for the MS (ISSI, GSSI, ASSI, V-ASSI, V-GSSI). The output xESI (IESI, GESI,
AESI, V-AESI, V-GESI) shall be a cryptographic address. Only MSs in a location area with the correct values of CCK
or SCK shall be able to identify messages addressed for their attention.
If the PDU is encrypted ESI shall be used in that PDU The use of signalling for AI encryption management is more
fully described in clause 6.5

Latest version (v1.7.0.0) can be found here: Release post

 

[LA6FRA]

I can not run anymore v.1.7.0.0 because McAfee antivirus recognize it as a virus, but it has been working perfectly before and for a while now.

 

[ScanHen]

I was asked to report this error

 

[thewraith2008]

I was asked to report this error

Was this error from the latest release (v1.7.0.0) of the plug-in?



Latest version (v1.7.0.0) can be found here: Release post

 

[ScanHen]

Was this error from the latest release (v1.7.0.0) of the plug-in?



Latest version (v1.7.0.0) can be found here: Release post

Yes

 

[hamradionl]

TETRA_error_LLC_2019-12-13_12-45-59.4712_burst.txt

CurrTimeSlot, 2
MAC_PDU_Type, 0
Fill_bit, 1
Position_of_grant, 1
Encryption_mode, 0
Random_access_flag, 0
Length_indication, 27
Address_type, 3
USSI, 11512921
Capacity_Allocation, 1
Granting_delay, 10
MacPduRealSize, 123
PduStartOffset, 0
LLC_Pdu_Type, 13
LLC_Pdu_SubType, 2
Flow_control, 0
Advanced_link_number, 3
Link_feedback_information_flag, 1
CRC_check: 15322

BURST[124]: 0011000011011011101011111010110001011001010001101001101100110010000001110111001111010010001001100111110000011000111110010111

 

[thewraith2008]

TETRA_error_LLC_2019-12-13_12-45-59.4712_burst.txt

CurrTimeSlot, 2
MAC_PDU_Type, 0
Fill_bit, 1
Position_of_grant, 1
Encryption_mode, 0
Random_access_flag, 0
Length_indication, 27
Address_type, 3
USSI, 11512921
Capacity_Allocation, 1
Granting_delay, 10
MacPduRealSize, 123
PduStartOffset, 0
LLC_Pdu_Type, 13
LLC_Pdu_SubType, 2
Flow_control, 0
Advanced_link_number, 3
Link_feedback_information_flag, 1
CRC_check: 15322

BURST[124]: 0011000011011011101011111010110001011001010001101001101100110010000001110111001111010010001001100111110000011000111110010111

Your posting something you have already sent to me and has been dealt with.

I might add that you sent it 3 months after it occurred and failed to send the screenshot which also shows additional information to debug the error.



Latest version (v1.7.0.0) can be found here: Release post

 

[RevWil]

Hey,

first of all, thanks for keeping the project alive.
I have a question for the wishlist:

Would it be possible in the future to create a function where you can use a custom sound for every new MS registration that is happening?
I'm talking about the actual "MS Registration" tab.



I'm not into coding at all so I'm asking with a lot of reservation.

Thank you and greetings

 

[syscodec]

I found the follow quote in the standards in relation to the encryption of the SSI (element of the Layer 2 MAC) for encrypted PDUs.
The following would seem to indicate that the SSI is always encrypted for encrypted PDUs.






Latest version (v1.7.0.0) can be found here: Release post

I have noticed (encrypted network) that SSIs (encrypted) remain same for a long time (many months MS has same encrypted SSI) before they are changed .... Also it could be possible (it is possible here where I live) to call to SSI from GSM network (it requires prefix + SSI) and if someone answers then the SSI probably is not encrypted

 

[hamradionl]

@RevWil,
ask the same

 

[hamradionl]

Your posting something you have already sent to me and has been dealt with.

never responded as received and solved, so 2 times better than none

 

[thewraith2008]

I have noticed (encrypted network) that SSIs (encrypted) remain same for a long time (many months MS has same encrypted SSI) before they are changed .... Also it could be possible (it is possible here where I live) to call to SSI from GSM network (it requires prefix + SSI) and if someone answers then the SSI probably is not encrypted

Yes calls to phones can occur via the E.164 Gateway. I've seen these on occasions.
These are private calls but you will only hear one side of call.
When used, the ISSI is 16777184. The other number should also be shown.

@ScanHen
Not sure why that error occurs.
I can see where it fails and there seems to be a issue with the length and elements repeating which they shouldn't be.
May something with it been a reconstructed PDU.

If you see that error again please send the error again so I can compare to what you already sent.



Latest version (v1.7.0.0) can be found here: Release post

 

[hamradionl]

Yes calls to phones can occur via the E.164 Gateway. I've seen these on occasions.

Local network use this function very often, what look like sort of group or conversation call, with 2 or more users same time.

 

[Ubbe]

Everything that can communicate in tetra systems has an issi. So each telephone patch will have it's own issi. Each console has it's own unique issi. Each server that can send or receive SDS messages has it's own issi.

/Ubbe

 

[hamradionl]

Is this possible ?
1 unit connect both to tetra and gsm the other units call in to this tetra-gsm is possible use the tetra-gsm as gateway from GSM to Tetra?

 

[Ubbe]

Tetra usually use a PBX inteface, that is like a phone exchange with trunked lines to the telephone company. It has one common phone number that people call from gsm or landline and that also will be displayed when tetra users call out using the phone interface but it will act as 16-32-64 normal phone lines that can have that many simultanious ongoing phone calls. It doesn't matter if calls go to/from gsm or landlines.

Usually when people call to the tetra system they get a connect tone and then dial the issi number. Some PBX setup have the phone company set up a whole number serie 555-5xxx-xxxx that the x's are the issi or perhaps just the last 5 digits in the issi.

If gsm/landline would like to speak to a talk group it is usually done by having a mobile tetra radio connected by a EM interface to the system that then use a voice activated transmit function and that tetra radio have an issi and are set to one specific TG.

/Ubbe

 

[Marco192]

Under MS Registrations on a encrypted network I sometimes see lines like this:

MS request for registration/authentication ACCEPTED for SSI: xxxxxx GSSI:xxxxx - Roaming location updating
BS result to MS authentication: Authentication successful or no authentication currently in progress SSI: xxxxxx - Authentication successful or no authentication currently in progress
MS request for registration/authentication ACCEPTED for SSI: xxxxxx GSSI:xxxxx - Attachment for next ITSI attach required - ITSI attach

Are those stations and groups that are being used unencrypted on a encrypted network or is the TTT showing some ISSI and GSSI info encrypted stations?

 

[Ubbe]

All radioterminals in a tetra system are registred in a database. The text only show that the ISSI is valid and it is accepted to be used with that TG according to the database. It has nothing to do with encryption. The database can validate an ISSI to be used with certain TG's and to use specific sites.

/Ubbe

 

[Marco192]

All radioterminals in a tetra system are registred in a database. The text only show that the ISSI is valid and it is accepted to be used with that TG according to the database. It has nothing to do with encryption. The database can validate an ISSI to be used with certain TG's and to use specific sites.

/Ubbe

I understand the part about registration and authentication of terminals, but my understanding was that all the traffic/network info was encrypted so that you can not see any ISSI and GSSI numbers.

 

[ET-NL]

According to the Tetra documentation this traffic can be encrypted, but on some networks they are in the clear.