Hacker News Reader

Comment by desdenova | Hacker News Reader

Good to see some people are actually solving this problem, unlike all those startups using it as a marketing buzzword.

The first time I can across PIR was via the 2014 blog post from Signal on how Private Contact Discovery was a hard problem and how it required PIR to be solved. https://signal.org/blog/contact-discovery/

Maybe this will help Signal get to a viable solution in a few years.

Note that Signal decided not to use that:

> Unfortunately, for a reasonably large user base, this strategy doesn’t work because the bloom filters themselves are too large to transmit to mobile clients. For 10 million TextSecure users, a bloom filter like this would be ~40MB, requested from the server 116 times a second if every client refreshes it once a day.

They decided to run computations inside a 'secure' hardware environment instead (SGX specifically) so that they can't get access to the computation themselves but it also doesn't need to be run client side. I assume you meant the former thing, but the approach they actually use is fundamentally different from homomorphic encryption / PIR.

How is SGX different from putting a sticker on the server rack door that says "don't open private data"? Just asking.

Unless you have an electron microscope, work at Intel, or manage to find a hardware exploit, you are not getting the private key out of that chip, which, short of breaking the underlying cryptography, is the only way you're getting at that data.

Except, of course, if you put malware in the next build of your mobile app, and grab it before it's encrypted. Which Signal easily could, and it probably wouldn't be spotted for weeks. Fundamentally, it's all about trusting other people.

I assume you're referring to the blockchain industry, but they've advanced cryptography a lot, specifically with zkproofs.

I know of the concept of zero-knowledge proofs, but didn't know that the blockchain industry advanced cryptography a lot in that area. What are the practical applications of those new things? Or which new things are there to begin with? The Wikipedia article on zero-knowledge proof doesn't seem to say

With zk you can prove you own something or sign transactions without people tracking your entire history. It is also used to help scale chains by rolling up multiple transactions into one proof.

One of the applications are ZK-Rollups [1] which allow developers to move heavy computation off a blockchain. The blockchain receives the results and only validates proofs that they are valid. This is especially useful on Ethereum because its computational throughput is pretty low.

There's also ZCash [2], which is a cryptocurrency that lets you make untraceable transactions. This is in stark contrast to Bitcoin or Ethereum, where transaction information is available publicly to everyone. They have a series of blog posts [3] on the math that actually makes it work under the hood.

[1] https://ethereum.org/en/developers/docs/scaling/zk-rollups/

[2] https://z.cash

[3] https://electriccoin.co/blog/snark-explain/

No, I'm referring to the FHE startups that are promising a lot of magic that isn't really feasible, while failing to solve what is feasible.

Reply on news.ycombinator.com