[ETH_start]

>>Why couldn't we have a private crypto currency backed by dollars or euros?

Yes, you can utilize dollar backed and dollar pegged stablecoins, like USDC and DAI, respectively, in privacy-shielding protocols like https://zk.money and https://tornado.cash.

The problem at the moment is that Ethereum has very limited scalability, and privacy-shielded transactions are about five to ten times more compute-intensive than vanilla transactions, making them prohibitively expensive to conduct for most applications.

Ethereum layer 2 solutions that preserve the base layer's decentralization hold the promise to make such transactions viable at scale, but they are still quite immature in their feature set. For example, all of the general computation L2s still rely on a centralized coordinator.