<i>Disclaimer:</i> I am a researcher in this space and also CTO of a company (Arwen.io) which builds cross-chain atomic swaps.<p>To me, one of the more powerful properties of blockchain-based cryptocurrencies is that they overcome a long standing impossibility result in cryptography:<p>fair exchange, i.e. atomic swaps, are impossible without a trusted third party [0].<p>Cryptocurrency-backed blockchains do this by modifying the underlying assumptions behind that impossibility result in two ways [1]:<p>1. it adds the assumption that at least one side of the exchange is trading a blockchain asset,<p>2. it the treats the blockchain holding that asset as a trusted party.<p>To someone outside the world of cryptocurrency this may seem like an odd set of assumptions. However if what you want to exchange is a blockchain asset, assumption 1 and 2 is very reasonable. Valuing a blockchain asset already assumes that the blockchain is trustworthy because the value and ownership of the asset requires a trustworthy blockchain.<p>A very cool result is that a party can perform a fair-exchange between a cryptocurrency and the solution to a problem in NP. For instance the ZKCP (Zero Knowledge Contingent Payment) protocol has been used to perform a fair-exchange of bitcoins for the solution to a Sudoku puzzle [2]. SIA coin uses a slightly different model to enable users to prove and collect cryptocurrency for storing another users data [3].<p>Taken to its logical conclusion, this seems like it would allow substituting information or math for currency. Could we build an economic in which hard currency is backed by proof-of-storage or solutions to problems in NP? When I was a teenager I read Richard Brautigan's poem in which a man replaces his plumping with poetry [4]. It was one of reasons I got into cross-chain trading research as it inspired me to think about how to replace cash with computation. Hopefully it works out better than for the protagonist of that poem who ends up living in YMCA. Brautigan, writing 50 years ago, captures both the promise [5] and downsides of information technology ecology projects like cybernetics and cryptocurrency.<p>[0]: On the impossibility of fair exchange without a trusted third party <a href="https://pdfs.semanticscholar.org/208b/22c7a094ada20736593afcc8c759c7d1b79c.pdf" rel="nofollow">https://pdfs.semanticscholar.org/208b/22c7a094ada20736593afc...</a><p>[1]: The Arwen Trading Protocols (Full Version) <a href="https://eprint.iacr.org/2020/024.pdf" rel="nofollow">https://eprint.iacr.org/2020/024.pdf</a><p>[2]: The first successful Zero-Knowledge Contingent Payment <a href="https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-announcement/" rel="nofollow">https://bitcoincore.org/en/2016/02/26/zero-knowledge-conting...</a><p>[3]: sia - about <a href="https://sia.tech/technology" rel="nofollow">https://sia.tech/technology</a><p>[4]: Homage to The San Francisco YMCA by Richard Brautigan <a href="http://www.rewindreduceandrecycle.com/richard-brautigans-homage-to-the-san-francisco-ymca/" rel="nofollow">http://www.rewindreduceandrecycle.com/richard-brautigans-hom...</a><p>[5]: All Watched Over by Machines of Loving Grace by Richard Brautigan <a href="https://en.wikipedia.org/wiki/All_Watched_Over_by_Machines_of_Loving_Grace" rel="nofollow">https://en.wikipedia.org/wiki/All_Watched_Over_by_Machines_o...</a> <a href="https://allpoetry.com/All-Watched-Over-By-Machines-Of-Loving-Grace" rel="nofollow">https://allpoetry.com/All-Watched-Over-By-Machines-Of-Loving...</a>