1. Ronald L. Rivest MIT ShafiFest January 13, 2019
Voting and ZK
Ronald L. Rivest
MIT
ShafiFest
January 13, 2019

2. Voting and Zero Knowledge
Over the next decade or so, zero knowledge protocols (Goldwasser, Micali, and Rackoff (1985)) may have major impact on how we vote
Cryptography supporting democracy!

3. How do we vote today?

4. 80% on paper ballots

6. 20% on ???
And Who Do You Hope You Voted For?

7. How might we vote in the future?

8. National Academies study
Report on ”Securing the Vote” issued September 2018
(159 pages; free pdf)
41 recommendations

9. Recommendations Use voter verifiable paper ballots everywhere by 2020
Audit election outcomes!
No Internet voting!
Conduct and assess pilots of end-to-end verifiable (E2E-V) voting systems.

10. E2E-V Voting Systems Pioneered by Chaum (2004) and Neff (2004)
Voter gets and submits encrypted ballot
Voter gets receipt (encrypted ballot)
Election web site posts all encrypted ballots (with voter names or voter IDs).
Election officials determine and post winner.
Tested in Takoma Park MD (2009; 2011); Designed into Travis County STAR-VOTE (2013)

11. ZK is everywhere
Voting machine proves to voter that her ballot encrypts her actual choices. To prevent vote-selling, voter doesn’t get encryption randomization.
Voting machines post proofs that posted ballots are encryptions of valid ballots (NIZKs).
Election officials post proof that announced winner is correct (NIZKs). Voter privacy ensured by use of homomorphic encryption or by use of mix-nets.

12. Thank you Shafi
for inventing ZK!