Codan 2110 series Reference Manual page 314

AES-256 digital voice encryptor option
To create a secure key for another secure index:
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1
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If the selected secure index is between 0 and 99, the index is shown
NOTE
as a 2-digit number.
Hold SEC, then scroll to Edit Key.
Press .
NOTE The currently selected secure index is highlighted.
Scroll to the secure index in which you want to create a new key.
Press .
Manpack Transceiver 2110 series Reference Manual