Is it legal? I thought the DMCA protects flimsy security of this kind by making it illegal to check if its flimsy.
I'm not sure what laws apply to you where you live so you'd have to check, but you could also do this on pen and paper if that helps :)
No idea what the DMCA says. It doesn't apply in most parts of the world, and also not where I live. So it's for sure legal somewhere.