There has been a lot of discussion over the past few months about this. The voting machines were created by a private company (MSA). The code was supposedly "open" but it was nowhere to be seen.
The machines basically print an electronic voting bill, that has an RFID chip which is reportedly vulnerable.
Still, this can be considered better than Brazil system: The code cannot be read by the population, the machine itself has secret proprietary components, testing its security is not truly allowed (the government claims to allow testing, but the test has rules to make true testing impossible, and the allowed tests pointless), and... the machine prints nothing, you are supposed to trust whatever it says the vote count is, without even being able to see if there are bugs or not in the vote counter (what if it has a loop with a > instead of >= for example, that causes 1 less vote per machine?)
The machines basically print an electronic voting bill, that has an RFID chip which is reportedly vulnerable.