Conversation

1\ A thought experiment: The year is 2277. You're the bartender at a spaceport in a faraway Earth colony on a planet orbiting α-Centauri: a distance of ~4 light years. Guy walks into your bar, slams down a credit chit, and asks for a drink. How do you know his money is any good?
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2\ If the credit chit were guaranteed by a bank or a blockchain or something local to α-Centauri it'd be easy, just like it is here on Earth in 2018. But say this guy is fresh-thawed after his long journey from Earth aboard a lighthugger. What kind of wealth could he even have?
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3\ He's unlikely to be carrying base metals. Like natural resources, they'd still be valuable, but too heavy to transport from Earth. Physical fiat (bank notes) wouldn't be accepted either: too easy to 3D-print forgeries. So what form of wealth survives interstellar voyages?
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4\ Information! Wealth transfer between stars must be digital. So the guy could present a statement from Bank of Orion or sign some blockchain transaction with his private keys to prove to you he is solvent. "One Corellian Ale, coming right up sir..."
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5\ But what if, just before arriving, the guy beamed a transaction back at Earth spending all his funds? It would take 4 years to get to Earth and 4 years for Earth to relay acknowledgement back to α-Centauri. During those 8 years, he could double-spend freely on α-Centauri!
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7\ Another problem: say two ships leave Earth and α-Centauri at the same time, each bound for the other. Later, both Earth and α-Centauri broadcast spends. Due to the relativity of simultaneity, the two ships will receive the spends in *the opposite order*! What should they do?
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8\ These examples are not pathologies. They are fundamental problems of interstellar commerce. I read a lot of sci-fi but I don't know of many authors who write about interstellar distributed consensus. Everyone writes about the engines, but the money is just as vital...
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Replying to
You're the second person in these responses to recommend that book. Is it any good? The ad copy for it suggests it's basically about exactly the scenarios I outline above... Damn, though, I can't wait for the golden age of crypto sci-fi. C'mon , get involved!