Nym's Plan to Boost Internet Privacy Through 'Mixnets'

Harry Halpin helped create uniform cryptography standards for the World Wide Web Consortium, reports Quanta magazine — but 'he also wanted to protect the lower, foundational level: the network through which the information is transmitted.

'In 2018, he started Nym Technologies to take on this problem.... Halpin spoke with Quanta from Nym's headquarters in Neuchâtel, Switzerland.'

Halpin: The trickier problem is this: How do I communicate with you so that no one else knows I'm communicating with you, even if our messages are encrypted? You can get a sense of what people are saying from the pattern of communication: Who are you talking with, when are your conversations, how long do they last...?

There are two key elements: One is the 'mixnet,' a technology invented by David Chaum in 1979 that my team has improved. It relies on the premise that you can't be anonymous by yourself; you can only be anonymous in a crowd. You start with a message and break it into smaller units, communications packets, that you can think of as playing cards. Next, you encrypt each card and randomly send it to a 'mixnode' — a computer where it will be mixed with cards from other senders. This happens three separate times and at three separate mixnodes. Then each card is delivered to the intended recipient, where all the cards from the original message are decrypted and put back into the proper order. No person who oversees mixing at a single mixnode can know both the card's origin and its destination. In other words, no one can know who you are talking to.

Q: That was the original mixnet, so what improvements have you made?

Halpin: For one thing, we make use of the notion of entropy, a measure of randomness that was invented for this application by Claudia Diaz, a computer privacy professor at KU Leuven and Nym's chief scientist. Each packet you receive on the Nym network has a probability attached to it that tells you, for instance, the odds that it came from any given individual.... Our system uses a statistical process that allows you both to measure entropy and to maximize it — the greater the entropy, the greater the anonymity. There are no other systems out there today that can let users know how private their communications are.

Q: What's the second key element you referred to?

Halpin: Mixnets, as I said, have been around a long time. The reason they've never taken off has a lot to do with economics. Where do the people who are going to do the mixing come from, and how do you pay them? We think we have an answer. And the kernel of that idea came from a conversation I had in 2017 with Adam Back, a cryptographer who developed bitcoin's central 'proof of work' algorithm. I asked him what he would do if he were to redesign bitcoin. He said it would be great if all the computer processing done to verify cryptocurrency transactions — by solving so-called Merkle puzzles that have no practical value outside of bitcoin — could instead be used to ensure privacy.

The computationally expensive part of privacy is the mixing, so it occurred to me that we could use a bitcoin-inspired system to incentivize people to do the mixing. We built our company around that idea.... A new paper that came out in June shows that this approach can lead to an economically sustainable mixnet....

We are not building a currency system or trying to replace the dollar. We just want to provide privacy to ordinary people.

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