Bitcoin is the leading cryptographic digital currency. Created in 2009 by the now possibly unmasked hacker Satoshi Nakamoto, it polarizes opinion. Some people promote it as the technical embodiment of a libertarian attack on the iniquity of "fiat currency" and the power of the state and big banks, an embodiment of a pure market of value untainted by regulation where everything really is worth only what people will pay for it. Others criticise Bitcoin, often savagely, for the same reasons and for what they perceive as its technical and social failings. But Bitcoin is interesting in ways that go beyond the concerns of its most vocal proponents and detractors.