Proving eligibility without revealing identity

Zero-knowledge proofs enable genuinely new kinds of privacy: proving you're over 18 without revealing your exact birthdate, proving you're a verified human without revealing which human, or proving you hold enough funds for a transaction without revealing your total balance. Each of these reveals only the single true-or-false fact required, nothing more.

This is a meaningfully different privacy model than 'hiding everything,' it's selective disclosure: you choose exactly what gets proven and nothing else leaks, which is closer to how privacy actually works in everyday life than an all-or-nothing approach.