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> With the recent introduction of zk rollups on Ethereum, it's now possible to have the best of both worlds, in my opinion (see https://aztec.network/index.html

> With the recent introduction of zk rollups on Ethereum, it's now possible to have the best of both worlds, in my opinion (see https://aztec.network/index.html https://aztec.network/index.html). Transactions that need to be private will be conducted on zero-knowledge rollups built for privacy. Mastercard is working on this with Consensys for Ethereum (https://www.coindesk.com/business/2021/12/16/consensys-colla https://www.coindesk.com/business/2021/12/16/consensys-colla...). I can’t find any real technical documentation on this system but from what I understand about ethereum, this kind of use case effectively needs to be run off the main ethereum blockchain? I just don’t understand what the purpose of the blockchain really is when most of the interesting ways to scale add features rely on processing transactions OFF the chain.

anchpop 5y ago
This is a misunderstanding. The goal of cryptocurrencies is not to process transactions. The goal is to order transactions. The order is the hard part. (Notice that if I have one ETH, and I submit a transaction to send alice an ETH and to send Bob an ETH, alice and bob are both very interested in the order - only one transaction can go through, and which one is determined by which one comes first in the chain). Fundamentally the order doesn’t really matter, as long as it doesn’t change retroactively. Once you have agreement on the order, anyone can process the transactions and know they’ll get the same final result as anyone else. I’m not sure about this specific one, but most “rollup”s use the main chain for agreement on the order, and then outsource the actual processing to someone outside the chain. Some use cryptography from verifiable computing, so the off-chain person can also submit a proof that their processing is right and there’s no possibility of fraud. (the proof can then be verified extremely quickly.)

anchpop 5y ago

This is a misunderstanding. The goal of cryptocurrencies is not to process transactions. The goal is to order transactions. The order is the hard part. (Notice that if I have one ETH, and I submit a transaction to send alice an ETH and to send Bob an ETH, alice and bob are both very interested in the order - only one transaction can go through, and which one is determined by which one comes first in the chain). Fundamentally the order doesn’t really matter, as long as it doesn’t change retroactively. Once you have agreement on the order, anyone can process the transactions and know they’ll get the same final result as anyone else. I’m not sure about this specific one, but most “rollup”s use the main chain for agreement on the order, and then outsource the actual processing to someone outside the chain. Some use cryptography from verifiable computing, so the off-chain person can also submit a proof that their processing is right and there’s no possibility of fraud. (the proof can then be verified extremely quickly.)