Based on blockchain technology, most cryptocurrencies have an open and public ledger. While this is required for these systems to work, it comes with a significant downside: Privacy is often quite limited. Government agencies, analytics companies and other interested parties — let’s call them “spies” — have ways to analyze the public blockchains and peer‐to‐peer networks of cryptocurrencies like Bitcoin, to cluster addresses and tie them to IP addresses or other identifying information.Unsatisfied with Bitcoin’s privacy features, several cryptocurrency projects have, over the years, launched with the specific goal to improve on them. And not without success. Several of these privacycoins are among the most popular cryptocurrencies on the market today.