AES256 prior to R2.4

Prior to R2.4 the method for AES 256bit encryption was not clearly defined in the DMR standard. As a result, Motorola used their own implementation of AES which would not work with other vendors radios (the same could probably also be said about other vendors).

Shortly before the release of R2.4, the standards relevent to AES encryption in DMR were finalised and some changes were made in the software to allow AES256 in MOTOTRBO radio to work with AES256 in other makes of radios. This also meant that radios, with firmware older than R2.4, would not work with radios that have firmware newer than R2.4.

There are two ways to resolve this:

1. Upgrade the firmware in all radios to something newer than R2.4 .
2. In radios with AES enabled, there is a tick box to allow legacy (Motorola) AES support.

If all your radios have firmware newer than R2.4, you dont need to do anything.