Figure 5: Sds End-To-End Encryption - Motorola MTP850 S Product Information Manual

40 | Services and Features
In air interface encryption, the receiving base station decrypts data which travels clear within the system domain. For
E2EE, the transmitting radio encrypts the data and the receiving radio or an E2E terminator located in the
infrastructure decrypts the data.
E2EE protects the SDS/SDS-TL data services both in TMO and DMO. The following TETRA data types are
protected.
• SDS type 4 with SDS-TL.
• SDS type 4 without TL.
For short data applications, the source data may come from an external application or from a task internal to the radio,
such as text messages or GPS. The radio passes only the internal text messages and GPS data for encryption by its
crypto engine.
The encrypted short data service is established between two end points. One end point is terminated in the radio, and
the other end point is terminated in a Short Data Encryption Gateway (SDEG) or another radio. The destination
address specifies the encryption type, that is, whether the packets are transmitted as encrypted, clear or dropped.

Figure 5: SDS End-to-End Encryption

Data Services
Message Display Service
and Other Embedded
Aplications
PEI
End-to-End SDS Encryption
Short Data Transport Layer
(with or without SDS-TL)
Short Data Service Type 4
Note: Key Management Facility (KMF) can manage and support only one short data association and a key
at the same time.
The radio selects the E2EE mode for the outgoing text message in accordance to the address association and
requirements for the E2EE High Security Mode. Depending on codeplug settings you can override the address
association and select using the MMI menu whether an SDS is sent to clear or encrypted contact (Group or Private
Number).
The radios support the high security mode configurable using the CPS. In this mode the association that binds the
address to a given cryptogroup is always mandatory.
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Standard TETRA Air Interface Encryption
and Key Management
TETRA System
Boundary
End-to-End Key Management