Post

The International Association for Cryptologic Research has used heliosvoting.org – my online voting system – for a number of years. This year, a trustee lost their secret key. The election has to be re-run. Below, a few thoughts that didn't fit in the NYT piece. www.nytimes.com/2025/11/21/w...

First, this is really unfortunate, and I feel really bad. Sure, you can say "the trustee should have saved their secret key", but ultimately, as a system designer, I want my systems to be resilient to human mistakes. To be human is to err. Although, it's really hard to strike the right balance.

And then you need to manage how the decryption of the tally is performed, and the only way we know how to do that reasonably well is by having a set of trustees where no single individual can go rogue and break privacy. But there's a very specific design tradeoff here.

Do you require all trustees to be present for decryption, or do you tolerate a minority of trustees to be absent? For resilience, it seems clear you should tolerate some trustees being absent. But that complicates the setup process: all trustees need to log in once, then a second time.

And of course this is where designing Helios for different audiences is really tricky. Some users, like the IACR, are super expert and they can go through the complex setup process. Other users don't even understand what a key is.