Just found out that the SME files are NOT encrypted. In fact the 'free versions' (SME) are missing a (fix sized) block of data from address 0008 to 0060 compared to the (payed) .cpf files.
From address 0060 up the .cpf file is identical to the .sme file.

What we have to find out : What data needs to be inserted from address 0008 to 0060?

Now I wonder: Do we all get the same smekey for e.g. SA2 Panflutes? (mine is 6E343A01134ECCAEA45C96ABF1A3****)