How do Electronic & Mechanical Voting machines work? And how do they provide accurate votes? Is it overly complicated machine, or is it surprisingly simple?

  • So far, none of the articles "how do voting machines work" found on Google actually explain ANY meaningful details, including one from SciAm.
    – user4012
    Commented Mar 2, 2017 at 1:17
  • @user4012 That's why i'm asking, I've looked but I just can't find anything, I want to a build a voting machine (For fun) but I don't know where to start.
    – Person
    Commented Mar 2, 2017 at 1:20
  • This's actually quite broad, a machine has an algorithm that tallies the vote and the machine itself.
    – Panda
    Commented Mar 2, 2017 at 1:58
  • Its kinda hard to answer your questions because the fundamentals are quite simple - scantron or OCR to recognize the tallies, and then just a count to.... count the tallies, plus some bells and whistles to prevent tampering - but the details are complicated and will vary machine to machine. Commented Mar 2, 2017 at 3:56

2 Answers 2


This is a very broad question, so any answers are going to be either very high-level or really long. I'm going to go for the former, but I encourage you to read the links I'm including, and then ask followup questions either here or on Information Security about specifics.

First of all, there are many voting machines in use across the country. Each state sets its own rules, purchases its own machines, and conducts its own elections (even if the day is Federally mandated). This page has a great deal of high-level information about the various voting machines, and you can drill down through the site to read more about each kind. One thing to note is that purely mechanical voting machines have been retired across the country (and I miss them!) - every machine is at least partially digital now.

Fundamentally, though, a voting machine consists of two parts: Voter input, and tallying. Voter input can be any way of inputting data into a computer (keyboard, touch screen, buttons, scantron, etc.). Tallying just means that the computer will keep a record of all the votes it sees. Depending on the state's laws and machine in question, this could be the official record, or simply a preliminary count used for quick election-night reporting.

Given how simple the basic functionality is, anyone with relevant knowledge can theoretically build a voting machine. However, the hard part is getting a state to use it, which usually means getting it certified in whatever manner the state requires. This page goes through a lot of the desired features in a voting machine, the groups that set the (voluntary!) standards that machines should meet, and which states require which levels of testing.

  • Would a state use software for a computer? Or would they totally discard it? If you were to strip down the computer to barebones, and have it run that program, take the and encrypt it in some way, store it so it cannot be accessed by the user, would the state at least consider the program?
    – Person
    Commented Mar 2, 2017 at 5:01
  • @Person - Read the link in the last paragraph, especially the "Testing and Certification of Voting Systems" section. If you can pass the current standards, or convince the government of a state that they should abandon their current standards, then yes it could be considered. But it's just as hard as getting any state law passed.
    – Bobson
    Commented Mar 2, 2017 at 5:15
  • 1
    @Person - friendly advice: the field if information security and cryptography is littered with failed efforts of novices who think they know how to do things. Ideas are easy. Implementations are what's hard. If a simple program running on commodity PC was enough to solve this problem; chances are one of the established players would have already done just that, and cornered the market.
    – user4012
    Commented Mar 2, 2017 at 14:53
  • 1
    @user4012, Re "chances are...": that presumes their customers actually want an inexpensive auditable machine. A corrupt buyer, (let's hypothesize that a dystopian few might exist...), would not prefer those features -- rather they might desire something obscure, expensive, impossible or difficult to audit, that could when required assure victory for a losing party.
    – agc
    Commented Mar 5, 2017 at 18:05

I can think of at least three kinds of voting machines.

  1. Mechanical, with levers. You pull down the lever for the candidate or option that you want. There usually are restrictions keeping you from selecting multiple choices in the same race (unless of course you are allowed to do that). When you finish making your selections, you press a button that records your choices and updates the internal tallies.

  2. Electronic scanner. Feed a paper ballot into a machine which scans the ballot to determine the choices. Usually keeps tallies as it goes.

  3. Touch screen. The modern electronic version of the mechanical voting machine. Often adds a confirmation screen showing the voter's choices. Confirmation clears the screen and updates the internal tallies. May or may not leave a paper trail.

And that's just the machines. Provisional and absentee ballots are often paper based and counted by hand.

Voting machines work in many different ways. How should voting machines work may well be a better question but is more discussion-based than objective. Some of the controversies involve

  1. Should there be a paper trail?
  2. If there is a paper trail, should it be voter verified? I.e. should we show the paper result to the voter and let them confirm or reject it.
  3. If there is a paper trail, how important is it that we not be able to determine who cast the vote?
  4. Should we be able to cancel votes cast by invalid voters?
  5. How important are quick results?
  6. How complicated are the counting systems?
  7. How important are unambiguous results? Florida in 2000 suggested that this was pretty important.
  8. How important is it that voting be intuitive?

These things contradict each other. A paper trail is easier to recount, but it is also easier to determine who cast which vote. Paper ballots are both anonymous and verifiable, but they are harder to count and less intuitive as the counting system gets more complicated. Anonymous votes prevent post-election cancellation if the voter is invalid. Voter drawn paper ballots are not unambiguous. Computer printed paper ballots require voter examination to be sure of casting the votes as intended, but that makes the system more complicated.

This is the general background. If you want something more specific, you'd need to ask a narrower question.

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