Seasons Greetings to all.

If you get bored with relatives and feasting today perhaps you might cast your eye over the below.

I have an electronic gadget that has a challenge response going on.

It sends me two bytes.
I have to respond with two bytes somehow derived from the ones it sent me.

I have a few examples below of correct challenges and responses.
Any ideas on how it is working and generating the response?

Challenge $E3 $C5
Response $82 $CB

Challenge $79 $71
Response $04 $35

Challenge $84 $15
Response $ED $85

Challenge $9B $B6
Response $6F $C9

Challenge $C7 $B0
Response $1A $DD

Challenge $AB $19
Response $9A $69

Many thanks and best wishes for the new year.