Authentication; Air Interface Encryption; Clear Radios (Class 1); Table 5: Security Features Required Per Security Class - Motorola MTP850 S Product Information Manual

42 | Services and Features

Authentication

Authentication establishes a level of a trust between a radio and SwMI. It is a challenge-response result protocol
between two parties based on their common knowledge of a secret key (K) to verify each others identity.
The SwMI authentication centre (AuC) provides a single K for authentication, which is shared only with the radio.
Authentication is always initiated by the SwMI, the radio can also authenticate the SwMI (if set by the service
provider).

Air Interface Encryption

The radio supports TETRA Air Interface Encryption (AIE) using the standard TETRA public encryption algorithms,
as defined in TETRA Security ETS 300 392-7, TEA1, TEA2 and TEA3. The focus of cryptography in TETRA is the
encryption key. TETRA AIE provides 12 000 000 000 000 000 000 000 000 key combinations.
TETRA TMO has three classes of encryption:
• Class 1 — clear (none).
• Class 2 — static key encryption (SCK).
• Class 3 — derived key encryption (DCK, sometimes called the dynamic key), the Common Cipher Key (CCK),
and the Group Cipher Key (GCK).
TETRA DMO has two classes of encryption: Class 1 and Class 2.
The security features supported in the radio depend on the security mode.

Table 5: Security Features Required Per Security Class

Security Feature
Radio Initiated Au-
thentication
SwMI Initiated Au-
thentication
Mutual Authentica-
tion
OTAR
SCK AIE
DCK AIE
GCK AIE
Note: In the current release the radio does not support the following security features:
• Radio initiated authentication
• Support for TEA4
• Explicit authentication during DGNA
Enhanced Security, which consists of TMO Air Interface Encryption class 3G and DMO class 2, is a selling feature.

Clear Radios (Class 1)

A radio can be configured as a clear radio. In such case the radio identifies itself in registration as a Security Class 1
radio and does not support encryption. A Security Class 1 radio does not contain any encryption algorithms in its
software.
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Mode
Security Class 1 Security Class 2
Not Allowed Not Allowed
Optional Optional
Optional Optional
N/A Optional
N/A Mandatory
N/A N/A
N/A N/A
Security Class 3 Security Class 3G
Not Allowed Not Allowed
Mandatory Mandatory
Optional Optional
Mandatory Mandatory
N/A N/A
Mandatory Mandatory
N/A Mandatory