TETRA. CryptoGateway

Germany is currently building a new digital voice and data radio system for its police forces, fire brigades and rescue services, customs authorities and intelligence services on the basis of the trunked radio technology TETRA (Terrestrial Trunked RAdio). This network allows for faster call setup, an improved audio quality and cross-country availability of a uniform service when comparing to its analogue predecessor. Yet the integrated tap-proof encryption system will provide the much needed confidentiality for e.g. the intra-police communication. As a specialty the German BOS digital radio system (BOS = public authorities and security organizations) will boast the world’s first nation-wide end-to-end encryption.

The Federal Office for Information Security (BSI) has developed a BOS smart card for the individual devices and a multi-channel crypto component (MKK) for the BOS control centers. Various radios with encryption technology on the basis of this BOS technology are available since quite a while there is still a lack of certified, full blown solutions to upgrade existing control center solutions respectively. The unavoidable complexity in developing such solutions requires the combination of very diverse competencies.

Sirrix.LS1 CryptoGateway

The Sirrix-LS1CryptoGateway provides an optimal solution to add support of the new BOS digital radio standard to existing control centers.  The complex cryptography and specific network interface technology will be abstracted to a great extent for control center applications. The MKK component with its up to 64 integrated smart cards is an inherent part of the Sirrix-LS1 CryptoGateway and remains completely hidden from the control center application. The connection to the TETRA switch (DXT) is achieved via a 2 Mb/s primary rate interface with 31 user channels at 64 kb/s each. These user channels as known in traditional ISDN scenarios are further partitioned into 8 TETRA channels such that a total of 248 speech channels become available. The TETRA-ACELP codec provides an audio quality close to the ISDN level despite the small bandwidth. Using standard web service functions (SOAP architecture) the control center application can simply assign ordinary VoIP channels to the TETRA group or single user calls.

Integration in the control center

The Sirrix-LS1CryptoGateway will be connected on the hand via the LS-1 interface with the BOS digital radio system. On the other hand it provides an Ethernet port for the access to its speech channels via standard VoIP protocols like SIP (µLAW- or GSM-coded) and RTP. The CryptoGateway is controlled via SOAP web services.

VoIP is used to talk with the forces in the field via single user or group calls while those channels are configured and set up via SOAP. The virtual actuation of the PTT button is effected with a simple web service call. With another web service call one can invoke an encryption or decryption service for data as received or sent via the LS-2 interface using the Short Data Service (SDS).