-science fiction, young adult
-main character was a male
-someone had made some kind of system where everyone had their own personal code - could be a bank password, savings code, etc. - but it was extremely private and considered unhackable. I think it was based on polynomials or factorials
-The conflict is that someone figures out how to hack everyone’s password, data is exposed
-main character has some kind of relationship to either the person that created the code or the person that hacked it. I think there’s a rivalry between the main character and another male
-there’s a really big twist in the middle of the book!
-might turn into a heist book? but also maybe not
-I *think* the original hardcover is blue/green, has overlayed code in the background, one modern-looking symbol. Possibly a key
-read in 2013/2014, and I had at least 2 books in the series out at the time, I’m only describing the first one. I was in 8th grade - 12 or 13 at the time. The book was age-appropriate
Could it be Artemis Fowl the Eternity Code? I haven’t reas it but the cover is just as you’ve described.
I think this could be Evil Genius, the first Genius Squad book by Catherine Jinks.