Bitcoin, the virtual currency composed of digital bits, is based on cutting-edge mathematical schemes that guard against counterfeiting.
But it's also based on an old idea, now dismissed by mainstream economists, about how a currency should operate - an idea that could be setting bitcoins up for an abrupt plunge.
Bitcoin was started in 2009 as a currency free from government controls, an entirely digital means of exchange for a digital age.
It's a rapidly growing phenomenon that has taken root as a payment method on some websites for both legal and illegal goods.
Image: In this April 3, 2013 photo, Mike Caldwell, a 35-year-old software engineer, poses with bitcoin tokens at his shop in Sandy, Utah, USA. Caldwell mints physical versions of bitcoins, cranking out homemade tokens with codes protected by tamper-proof holographic seals, a retro-futuristic kind of prepaid cash. With up to 70,000 transactions each day over the past month, bitcoins have been propelled from the world of Internet oddities to the cusp of mainstream use, a remarkable breakthrough for a currency which made its online debut only four years ago.
Text: Peter Svensson,Associated Press Technology Writer