When Satoshi published the Bitcoin whitepaper in 2008, it emerged directly from the cypherpunk tradition. Bitcoin solved the double-spend problem without a central authority. For the first time, people could transfer value over the internet without banks, intermediaries, or permission.

But there was a glaring problem: Bitcoin wasn’t private.

The blockchain is entirely public. Every transaction, every address, every balance is visible to anyone who cares to look. Satoshi acknowledged this limitation, suggesting users could preserve some privacy by generating new addresses for each transaction. That was a weak mitigation then. It’s nonexistent now, given the sophistication of chain analysis.

Satoshi also acknowledged something more telling. In a 2010 Bitcointalk post, he wrote: “If a solution was found, a much better, easier, more convenient implementation of Bitcoin would be possible.” He was talking specifically about privacy. The cryptography to solve it ...