Wouldn’t it be nice to allow the space occupied by the NONCE to be used for other things as well as encryption data?
In the specification, we have the case that if bits 3…4 of the TYPE are set to 0b00 then there is no encryption, and bits 5…6 which are the encryption subtype will be unused. How about extending this so that when their is no encryption, bits 5…6 are used to describe the contents of the NONCE field, which is no longer a NONCE field. For example bits 5…6 with a value of 0b00 would mean unused, 0b01 would mean text (name, locator, etc), 0b10 could be APRS in MIC-E format, leaving 0b11 free for now. That way we would have extra space for data which will be repeated without taking away any bandwidth from the audio. It would mean that the fragment LSF would need constant decoding since it could have multiple data types, and could also include changed APRS data.
Having this data does not preclude encryption, it just means that the encryption data would be sent slightly less often, but presumably that data wouldn’t change during the duration of the transmission anyway. Typically for the initial Link Setup Frame, if encryption is being used, then the NONCE would be used for the encryption data, and the other data would appear un the fragment LSFs during the transmission. If encryption is not being used then the initial Link Setup Frame would contain one of the other data items if used, like the text field.