One day in 2017-2018 I was lurking a cryptocurrency forum. Any specific information wasn’t being searched. Then the widely known in crypto circles Esperanto word appeared on my screen. I saw it many times, but this time was different. Suddenly, I got an insight into how to move forward the Black project that was started in 2014. A lot of thought was given to it, resulting in names Blacknet, BlackCash and BlackGateway.
A financial privacy is desirable, but it’s not necessarily tied to a core of a blockchain. Blacknet provides a transparent blockchain, and BlackCash is implemented as an application that operates on its own fungible token. An efficiency of privacy-preseving technologies is a worry. One approach is to deal with a chosen anonymity subset. In this case transaction data can be hidden as follows: a sender by a ring signature, an amount by a range proof, a reciever by a stealth address. While it’s possible in our environment, in practice end users are likely to send transactions in a privacy-leaking way. Second approach is to deal with an anonymity set of all users. In this case transaction data can be hidden by commitments and zero-knowledge proofs. ZK-STARK is seen as a most promising solution despite proof sizes because it doesn’t require a trusted setup.
Blacknet works well, albeit without blockchain applications. So I’ve resumed the exploration of BlackCash. The zero-knowledge technology progressed, and modern zk-SNARKs don’t require the trusted setup. It was discovered that the privacy may actually enhance the securiry of the asynchronous proof of stake. A possibility and implications of moving BlackCash into the base layer of Blacknet are being investigated.