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36 | Services and Features
Figure 5: Voice and Data End to End Encryption
Data Services
Voice Codec
End-to-End Encryption
PEI
Standard TETRA Air Interface Encryption
and Key Management
The End-to-End Encryption (E2EE) feature resolves this issue by encrypting the voice information before it is packed
into the PDU. This message is also encrypted according to the over-the-air encryption of the TETRA standard. Thus,
when the base station decrypts the PDU containing voice information, the voice part remains protected by encryption
until the called radio receives the voice and decrypts it.
The Universal Crypto Module (UCM), located in the radio, carries out voice encryption. The UCM takes the voice
stream and encrypts this stream using a set of keys. Likewise, the UCM takes encrypted voice stream and using the
same keys decrypts back into clear voice.
The encryption of voice and data can be carried out using a dedicated SIM card reader.
In the end-to-end encryption feature, the radio notifies and informs whether the call, being made or received, is voice-
encrypted.
This feature is relevant for group calls in TMO and DMO.
Radio Disable/Enable
On reception of an appropriate TETRA signaling for subscription disable with the correct SSI and MNI of the radio,
the radio becomes disabled.
When disabled, the radio does not participate in any voice call and ignores all supplementary services sent on the
downlink. All visible and audible indications are disabled, and the radio appears to be turned off. All user inputs (key
presses, knob operation) are ignored, and the PEI interface is closed.
The radio continues to perform mobility management functions, such as roaming, to facilitate subsequent enabling (or
further disabling).
The radio stores the disabled/enabled state in the codeplug, so the unit remains in that state after turning on.
If the radio is in the disabled state, and receives an appropriate TETRA signaling for subscription enablement with the
correct SSI and MNI, it restores to its normal operative state.
The TEI Query feature provides TEI information to the infrastructure during registration. This allows to disable the
radio by sending an appropriate TETRA signaling for equipment disable with the correct TEI for this radio. Replacing
the SIM card does not activate the radio.
If the radio is in the equipment disabled state, and receives an appropriate TETRA signaling with the correct TEI, the
radio restores to its normal operative state (if the subscription is also in the enabled state).
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TETRA System
Boundary
End-to-End Key Management
Short Data Service Type 4
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