The cryptography behind e-voting (and why paper ballots are still essential)

48 pointsposted 3 days ago
by acossta
(blog.trailofbits.com)

22 Comments

atoav

2 days ago

I am fascinated by the cryptography behind e-voting. That being said I am still against it for high stakes elections.

My main reason is that the purpose of elections is not just to figure out the preferences of the electorate, the main purpose is to deliver agreeable consent. And that means a big part of elections beyond the technical process of figuring out public sentiment is convincing everybody involved that the process itself is orderly. And it turns out the best way to do that is to make the process simple and understandable and involve people from all parties and from all walks of life as little cogs within the actual system.

Now yes, you can mathematically proof correctness of certain e-voting processes. But that proof does not give you the trust of the general population. We vote because we want to avoid having a civil war every time public sentiment shifts. Trust is everything. While we nerds may think there is nothing better than maths to do that, the relationship normal people have with computers is basically one where some foreign power constantly changes how their computer works. Ir is not a device that inspires incredible trust and transparency. It took me two decades to come close to understanding how computers work and even I would rather trust the paper ballot system than some e-voting system if my life and my countries future depended on it and I have to assume that the very chips on which that system runs may have backdoors. And even if I verified that they didn't, how can I know that I didn't miss anything on election day? No thanks.

darkamaul

3 days ago

I see two main benefits of using paper ballots. The first one is that is easy to explain and everyone understand how it works. Your grandparents, probably your kids of a certain age... When you start talking about electronic voting, the system becomes much more complex, and you need to trust someone else assessment of the system.

The second one is that you can enrol interested people in the process, for instance during the vote counting. In France, any voter can register to participate during the night. This creates a sort of community engagement which is extremely important in my opinion.

tatersolid

3 days ago

Voting officials should be selected by sortition at all levels, similarly to jury pools. Allowing self-selection can allow for collusion or a biased pool of election workers and judges, especially in cities/towns with an established single-party patronage bureaucracy.

franga2000

3 days ago

For election officials, you don't want a representative sample, you want a maximally diverse sample. If a certain party has e.g. 40% support and you randomly draw 6 election workers per polling place, the chance of giving them 50% or more on any polling place is quite high. Include some adjacent parties and you'll get some very one-sided groups.

Of course, you can't do a lottery and then demand the chosen self-identify which party they support, nor can you trust them to be honest. The result is that you can only have people who volunteer.

I think the system we have in Slovenia is quite close to optimal: every party who got at least X % in the last election gets to submit applicants and each polling place gets 6 people, who have to have been referred by different parties, with priority based on the rank of the party in the last election.

tatersolid

2 days ago

> nor can you trust them to be honest

We trust juries with locking people up for life if necessary and settling billion-dollar lawsuits. That’s the beauty of sortition. Most randomly selected people are honest instead of biased party functionaries.

Even if you got 3/4 registered Republicans at one polling location via sortition, the chances of those being people willing to cheat the election is very small as they are random citizens.

Similar to jury selection you would probably keep identity and assigned location secret by law until Election Day to prevent tampering.

gucci-on-fleek

2 days ago

> Voting officials should be selected by sortition at all levels

It's actually a pretty hard job, so I don't think that that's very realistic. I've worked as voting officer a few times in Canada, and it's a ~15 hour shift with maybe an hour of breaks total (or if you're unlucky, zero breaks), you need to be quite organized since there's so much paper, and it's quite stressful due to the volume of voters (some of whom tend to be quite angry).

The actual procedures are fairly simple, but you need to do them ~300 times in a day, without making any mistakes, while being rushed by the long lines. Anybody on HN could probably handle this (it's only a single 3-hour training course), but it's probably beyond what a substantial portion of the population is capable of, so sortition probably wouldn't lead to great results.

> Allowing self-selection can allow for collusion or a biased pool of election workers and judges, especially in cities/towns with an established single-party patronage bureaucracy.

In Canada, any candidate can send up to 2 people to each ballot booth to observe the procedures and ensure that all the rules are correctly followed, and most serious contenders tend to send at least 1 person to each polling place. So this should help to prevent collusion in most cases.

potamic

2 days ago

It's also a distributed system. To compromise the system you have to compromise multiple nodes which is more difficult. An electronic system can be compromised by a powerful entity if they wield influence over the individuals managing the tech.

gremlinunderway

3 days ago

I mean, electronic voting is just as easy to explain too. You push a button, it records your vote.

The complex part comes with answering how the system maintains the integrity of the ballot rather than just "how it works". In both cases when you simplify it, its equally understandable.

How exactly do we guarantee that paper ballots prevent fraud? Explain that in a simplified way, and it gets just as complex when you look into the bureaucracies that manage this in different countries.

franga2000

3 days ago

I can (and regularly do) explain the security of our elections in a few sentences that everyone has understood so far. I almost have a masters in CS and I can only understand like half of what Helios Voting does.

- committees are made up of 6 people that have to be nominated by 6 different parties - 3 of them must be on the polling place at all times - 2 of them must have eyes on the ballot box at all times - all 6 are present for the counting - the higher-level comission (chosen by the same system) double-checks uncounted ballots - everyone checks that their partial result is correct on the website - anyone can check that the published partial results are summed correctly

Boltgolt

3 days ago

"there are never fewer than 4 eyes on the ballot box" doesn't seem too complex to me

waterTanuki

3 days ago

> I mean, electronic voting is just as easy to explain too. You push a button, it records your vote.

It's never that simple. The beauty of pen & paper is that nothing can possibly go wrong short of having a stroke or seizure in the voting booth that will cause your vote to be miscounted or go to the wrong candidate.

A button has many things that can go wrong. Short circuit? Software bug? Neutrinos going through the earth happen to hit the circuit in such a way that your vote switches?

Electronic voting WITH paper ballot verification is a good middle ground, but no voting process should ever omit paper ballots for confirmation and hand-recounts.

Spivak

2 days ago

Right but mail in voting kind of disproved the need for all of this ceremony. You can cast your vote remotely and it works just fine. States even hold elections entirely by mail. It would be annoying but you could exactly replicate the mail in voting system in all aspects with email. You would for free get an even better confirmation that your vote was received because they would send you back the hash of your sealed ballot attachment and you could check it against yours. It's not exactly practical or accessible but it would be exactly as secure and hand recountable after the fact.

Okay now take the exact annoying system and replace only the sending an email with uploading your sealed ballot to a web form. Changing nothing except removing a 3rd party from the delivery mechanism—even more secure. Congrats you just invented e-voting.

theluketaylor

2 days ago

There is still tons of ceremony for mail in ballots, it just happens asynchronously to the voter making selections. That's true of paper ballots as well, as significant parts of the ceremony happens after the poll closes during the count.

The biggest problem is that email and online voting suffer from a lack of anonymity.

In person: voter eligibility is confirmed and marked executed, voter makes selections, ballot securely placed in box without being read.

Mail: voter eligibility is confirmed, ballot sent, voter makes selections, voter mails ballot back secured against tampering, voter eligibility is re-confirmed and marked executed, ballot securely placed in box without ever being read.

In both cases all the poll worker steps are overseen by election scrutineers who can confirm all legal requirements were adhered to, in particular that no one knows who anyone voted for, just that the vote was collected.

Email cannot replicate the separation of the voter eligibility verification with the ballot counting. No matter what you do there will always be pathways to link a specific voter to the ballot they cast.

Spivak

2 days ago

> Email cannot replicate the separation of the voter eligibility verification with the ballot counting

Yes it can, that's what I was on about with the whole "sealed" ballot thing but didn't feel like harping with the details. Once you fill out your ballot you encrypt it with your state election official's election specific public key and the attach it to the email—the digital "put it in the inner envelope." Poll worker confirms eligibility and puts just the encrypted ballot in the drop box. At this point in the process they couldn't look at the vote even if they wanted to. Then when it's time for counting they decrypt each one and count it.

Again is it practical or accessible to your grandma? No but it's exactly the same as mail in voting.

theluketaylor

2 days ago

There is absolutely no way to guarantee the process of detaching the outer ballot from the inner one doesn't retain a link to the voter. There are problems on 2 levels: the math proofs behind cryptography involved (which is being worked on, but not currently solved) and the building a verifiable implementation that honours all the requirements in a provable way. That's currently easier, but fails hard on the public trust front due to the overwhelming complexity.

Moving mail ballots to email is not currently possible or even very viable.

Spivak

14 hours ago

Well yeah the poll worker could just write the voter's name on the inner envelope but that isn't a deal breaker. There's no need for math proofs or whatever nonsense. The cryptography is just to provide a light barrier to the poll worker who's being observed detaching the two things just the same as mail in ballots like the glue on the inner envelope. It doesn't need to be verifiable or perfectly secure because again mail in ballots aren't. Someone could steam the glue off, look at the ballot, and reseal it (or replace it entirely) but that doesn't happen because they're being observed.

The point of this exercise isn't to say we actually do email in voting but to demonstrate that you can absolutely build a system that's exactly as understandable and trustworthy as the mail in ballot system but digital because it is the mail in ballot system just s/USPS/a series of tubes.

theluketaylor

13 hours ago

The poll worker executing mail in ballots can be completely observed without any special skills or tools.

Even a fully trustworthy poll worker executing an email workflow can’t be fully observed. The code they are running can betray the vote.

XKCD 2030 remains fully accurate. Electric voting: run away.

Spivak

10 hours ago

I get wanting to be wary of bespoke voting software but in this hypothetical it's a human watching the screen of a boring Windows workstation provided by the state's IT department as the poll worker uses Microsoft Outlook and puts ballots in a folder. At what point is the threat vector remote enough with these devices we're fine trusting literally everything else in our lives to that it's paranoia rather than a legitimate threat? I mean even if you are that paranoid let anyone who cares analyze the machine afterward I guess. And in this system recounts are trivial, you still have all the original data.

user

3 days ago

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