No electronic system is deemed impossible to hack. That said, the system we have in Brazil relies on way more than just technical measures to ensure the securit

No electronic system is deemed impossible to hack. That said, the system we have in Brazil relies on way more than just technical measures to ensure the security. There are statistical controls, processes are transparent and follow standards. Parties officials and technicians are involved in all steps. But back to tech, since this is HN, parties can ask for the actual source code, tool chain (regular GCC) and binaries used; and verify the compilation themselves against published hashes. The individual machines do the tally and print public results at the end of the day before any kind of central connection. All the central office does is sum those results. Thus any successful attack must happen at machine level, prior to Election Day. There are hundreds of thousands of machines from many different HW generations being used in a given election; all of them air gaped. Loading rogue software without cooperation requires tampering undetected with trusted execution modules that validate binaries twice, before and after election to avoid scrutiny. If you assume cooperation, you have to assume the collusion of way too many civil servants, from high court judges that oversees the processes appointed by parties of different colors, to low level tech folks who operates and validate much of the process. All in all, pulling an undetected fraud here would be a massive, Hollywood-level hacking feat. And in almost 30y no major election came close to being suspect of fraud.