Schneier on Security
A blog covering security and security technology.
April 14, 2005
Hacking the Papal Election
As the College of Cardinals prepares to elect a new pope, people like me wonder about the election process. How does it work, and just how hard is it to hack the vote?
Of course I'm not advocating voter fraud in the papal election. Nor am I insinuating that a cardinal might perpetrate fraud. But people who work in security can't look at a system without trying to figure out how to break it; it's an occupational hazard.
The rules for papal elections are steeped in tradition, and were last codified on 22 Feb 1996: "Universi Dominici Gregis on the Vacancy of the Apostolic See and the Election of the Roman Pontiff." The document is well-thought-out, and filled with details.
The election takes place in the Sistine Chapel, directed by the Church Chamberlain. The ballot is entirely paper-based, and all ballot counting is done by hand. Votes are secret, but everything else is done in public.
First there's the "pre-scrutiny" phase. "At least two or three" paper ballots are given to each cardinal (115 will be voting), presumably so that a cardinal has extras in case he makes a mistake. Then nine election officials are randomly selected: three "Scrutineers" who count the votes, three "Revisers," who verify the results of the Scrutineers, and three "Infirmarii" who collect the votes from those too sick to be in the room. (These officials are chosen randomly for each ballot.)
Each cardinal writes his selection for Pope on a rectangular ballot paper "as far as possible in handwriting that cannot be identified as his." He then folds the paper lengthwise and holds it aloft for everyone to see.
When everyone is done voting, the "scrutiny" phase of the election begins. The cardinals proceed to the altar one by one. On the altar is a large chalice with a paten (the shallow metal plate used to hold communion wafers during mass) resting on top of it. Each cardinal places his folded ballot on the paten. Then he picks up the paten and slides his ballot into the chalice.
If a cardinal cannot walk to the altar, one of the Scrutineers -- in full view of everyone -- does this for him. If any cardinals are too sick to be in the chapel, the Scrutineers give the Infirmarii a locked empty box with a slot, and the three Infirmarii together collect those votes. (If a cardinal is too sick to write, he asks one of the Infirmarii to do it for him) The box is opened and the ballots are placed onto the paten and into the chalice, one at a time.
When all the ballots are in the chalice, the first Scrutineer shakes it several times in order to mix them. Then the third Scrutineer transfers the ballots, one by one, from one chalice to another, counting them in the process. If the total number of ballots is not correct, the ballots are burned and everyone votes again.
To count the votes, each ballot is opened and the vote is read by each Scrutineer in turn, the third one aloud. Each Scrutineer writes the vote on a tally sheet. This is all done in full view of the cardinals. The total number of votes cast for each person is written on a separate sheet of paper.
Then there's the "post-scrutiny" phase. The Scrutineers tally the votes and determine if there's a winner. Then the Revisers verify the entire process: ballots, tallies, everything. And then the ballots are burned. (That's where the smoke comes from: white if a Pope has been elected, black if not.)
How hard is this to hack? The first observation is that the system is entirely manual, making it immune to the sorts of technological attacks that make modern voting systems so risky. The second observation is that the small group of voters -- all of whom know each other -- makes it impossible for an outsider to affect the voting in any way. The chapel is cleared and locked before voting. No one is going to dress up as a cardinal and sneak into the Sistine Chapel. In effect, the voter verification process is about as perfect as you're ever going to find.
Eavesdropping on the process is certainly possible, although the rules explicitly state that the chapel is to be checked for recording and transmission devices "with the help of trustworthy individuals of proven technical ability." I read that the Vatican is worried about laser microphones, as there are windows near the chapel's roof.
That leaves us with insider attacks. Can a cardinal influence the election? Certainly the Scrutineers could potentially modify votes, but it's difficult. The counting is conducted in public, and there are multiple people checking every step. It's possible for the first Scrutineer, if he's good at sleight of hand, to swap one ballot paper for another before recording it. Or for the third Scrutineer to swap ballots during the counting process.
A cardinal can't stuff ballots when he votes. The complicated paten-and-chalice ritual ensures that each cardinal votes once -- his ballot is visible -- and also keeps his hand out of the chalice holding the other votes.
Making the ballots large would make these attacks harder. So would controlling the blank ballots better, and only distributing one to each cardinal per vote. Presumably cardinals change their mind more often during the voting process, so distributing extra blank ballots makes sense.
Ballots from previous votes are burned, which makes it harder to use one to stuff the ballot box. But there's one wrinkle: "If however a second vote is to take place immediately, the ballots from the first vote will be burned only at the end, together with those from the second vote." I assume that's done so there's only one plume of smoke for the two elections, but it would be more secure to burn each set of ballots before the next round of voting.
And lastly, the cardinals are in "choir dress" during the voting, which has translucent lace sleeves under a short red cape; much harder for sleight-of-hand tricks.
It's possible for one Scrutineer to misrecord the votes, but with three Scrutineers, the discrepancy would be quickly detected. I presume a recount would take place, and the correct tally would be verified. Two or three Scrutineers in cahoots with each other could do more mischief, but since the Scrutineers are chosen randomly, the probability of a cabal being selected is very low. And then the Revisers check everything.
More interesting is to try and attack the system of selecting Scrutineers, which isn't well-defined in the document. Influencing the selection of Scrutineers and Revisers seems a necessary first step towards influencing the election.
Ballots with more than one name (overvotes) are void, and I assume the same is true for ballots with no name written on them (undervotes). Illegible or ambiguous ballots are much more likely, and I presume they are discarded. The rules do have a provision for multiple ballots by the same cardinal: "If during the opening of the ballots the Scrutineers should discover two ballots folded in such a way that they appear to have been completed by one elector, if these ballots bear the same name they are counted as one vote; if however they bear two different names, neither vote will be valid; however, in neither of the two cases is the voting session annulled." This surprises me, although I suppose it has happened by accident.
If there's a weak step, it's the counting of the ballots. There's no real reason to do a pre-count, and it gives the Scrutineer doing the transfer a chance to swap legitimate ballots with others he previously stuffed up his sleeve. I like the idea of randomizing the ballots, but putting the ballots in a wire cage and spinning it around would accomplish the same thing more securely, albeit with less reverence.
And if I were improving the process, I would add some kind of white-glove treatment to prevent a Scrutineer from hiding a pencil lead or pen tip under his fingernails. Although the requirement to write out the candidate's name in full gives more resistance against this sort of attack.
The recent change in the process that lets the cardinals go back and forth from the chapel into their dorm rooms -- instead of being locked in the chapel the whole time as was done previously -- makes the process slightly less secure. But I'm sure it makes it a lot more comfortable.
Lastly, there's the potential for one of the Infirmarii to do what he wants when transcribing the vote of an infirm cardinal, but there's no way to prevent that. If the cardinal is concerned, he could ask all three Infirmarii to witness the ballot.
There's also enormous social -- religious, actually -- disincentives to hacking the vote. The election takes place in a chapel, and at an altar. They also swear an oath as they are casting their ballot -- further discouragement. And the Scrutineers are explicitly exhorted not to form any sort of cabal or make any plans to sway the election under pain of excommunication: "The Cardinal electors shall further abstain from any form of pact, agreement, promise or other commitment of any kind which could oblige them to give or deny their vote to a person or persons."
I'm sure there are negotiations and deals and influencing -- cardinals are mortal men, after all, and such things are part of how humans come to agreement.
What are the lessons here? First, open systems conducted within a known group make voting fraud much harder. Every step of the election process is observed by everyone, and everyone knows everyone, which makes it harder for someone to get away with anything. Second, small and simple elections are easier to secure. This kind of process works to elect a Pope or a club president, but quickly becomes unwieldy for a large-scale election. The only way manual systems work is through a pyramid-like scheme, with small groups reporting their manually obtained results up the chain to more central tabulating authorities.
And a third and final lesson: when an election process is left to develop over the course of a couple thousand years, you end up with something surprisingly good.
Rules for a papal election
There's a picture of choir dress on this page
Edited to add: The stack of used ballots are pierced with a needle and thread and tied together, which 1) marks them as used, and 2) makes them harder to reuse.
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