For simplicity lets assume the first three bytes are. 102 075 & 179

Now I am making few assumptions for a practical implementation of the technique.

PAT() = Units place of sum of all digits. (no claims made,just for an example)

Now I can replace the three bytes with the following values 033 and 036

I have also specially stated the challenges of retrieving this information as as of not there are no built in integrity checks.