2-38 Services and Feature Description
6866537D87-F Chapter 2 - MTM800 Product Information Manual September 2008
Benefits:
❏ Increased security, better protection of sensitive voice, data, identities and signalling
information.
❏ Regularly changing the keys makes the TETRA services more difficult to crack by potential
attackers.
❏ DCK is a new Key at each Authentication (Logon), and is never send “over air”.
❏ CCK is known to all Group members, and is changed daily.
❏ GCK is known to dedicated Group members, and is changed every 3 months by default.
11.3.4 Encryption Mobility
A Class 2 or Class 3 terminal will also be able to operate on a lower class SwMI if it is provisioned to
allow this. A terminal that is provisioned to not allow operation on a lower class SwMI, will not
register on such a cell.
A Class 2 or Class 3 terminal upon camping on a cell that supports an SCK/CCK/GCK that the
terminal possesses, will apply AI Encryption to the registration PDU. If no acknowledgement is
received, the terminal will then send the registration in clear.
11.3.5 Encryption MMI
A Class 2 or Class 3 terminal that is involved in a clear call, will provide a visual as well as an
audible indication to the user that the call is not encrypted.
11.3.6 AIE Key Storage
The terminal stores all the keys, SCK/CCK/DCK/GCK, in a sealed manner in non-volatile memory of
the terminal - but not in the codeplug.
The terminal supports loading of the keys via a Key Variable Loader (KVL) tool.
By using a special secret key combination it is possible for a user to delete the cipher keys in the
terminal. This can be provisioned to erase either all keys or only the long-term keys.
11.3.7 User Key Deletion
User can delete Encryption & / or Authentication keys by a special sequence from the keypad.
Benefits:
❏ This allows user to clear the keys e.g. for transit.
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