This document summarizes a presentation about Helios, a web-based verifiable voting system. It discusses how Helios aims to improve the auditability of online elections using probabilistic encryption, homomorphic tallying, and other technical concepts. The presentation provides examples of Helios being used for university elections at Université catholique de Louvain and Princeton University. Open problems mentioned include supporting other programming languages like Java and ensuring voters can prove their votes were tallied correctly.

1. Helios
web-based
truly verifiable voting
Ben Adida
Harvard University
MSR Voting Technology Workshop
19 March 2010

2. “Web Based????”
- many elections are happening
on the web already, whether we like it or not.
- online elections are the least auditable of all:
you can’t even watch the ballot box.
- opportunity for a clear win:
improve auditability of elections that will
happen online no matter what.
- risk: people will think web-based voting
is okay for all eelections.

3. Low-Coercion
- web-based elections assume
low coercion already.
- If the voting public is a subset of the population,
there may be inherent limits to coercion.
- e.g. university voting

4. Technical Concepts
- Probabilistic Encryption & Threshold Decryption.
posting ciphertexts safely on a web site
- Homomorphic Tallying.
no write-ins, proofs of correct plaintext
- Benaloh Challenge.
cast or audit, authenticate only upon cast
- In-Browser Encryption.
plaintext only in user’s browser

5. "Obama"
Encrypted
Ballot
Alice
"AUDIT" "CAST"
Decrypted Signed
Ballot Encrypted
Ballot
Alice Alice
Encrypted Decrypted
Ballot Ballot
Signed
Encrypted
Ballot
VERIFICATION
Alice
http://en.wikipedia.org/wiki/Image:Barcode-scanner.jpg

6. Helios System Details
- Python & JavaScript logic & crypto
- Free/Open-Source stack
- Deployed on Google App Engine
- Deployed on Apache/Python/PostgreSQL
- Customizable
authentication, look-and-feel, translations

7. So, does it work?
- Université catholique de Louvain
25,000 eligible voters - 5000 votes
University president election
Helios 2.0, optimized
customized for UCL (French, improved UI)
- Princeton University undergraduate government
5000 eligible voters - 1500 votes
authentication integration with CAS
Helios 3.0a

8. Université catholique
de Louvain
[de Marneffe, Pereira, Quisquater]
8

9. 9

10. 10

11. 11

12. 12

13. most fun tidbit
in the first round,
the leader was
short of winning
by 2 votes out of 5000.

14. most interesting lesson
spurious claims
are easily countered

15. Princeton
15

16. Princeton Winter 2009 Runoff Election, # votes cast per class per hour
80
60
40
2010 2011 2012 2013
20
0
16

17. most interesting lesson
voting is error-prone ;
true verifiability can help recover

18. vote here
http://tinyurl.com/mshelios

19. Open Problems
- Java!
- additional ways of ensuring that the
same booth code is run by all.
- giving a choice to voters to do a true
interactive proof of the vote they actually cast.
- STV?
- Deep Issue: is enforced privacy over?

20. Questions?
ben_adida@harvard.edu
http://heliosvoting.org/