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Bitcoin: under the hood

istock/Tim Bruchhaus

Six years after it was sent out into the world, the significance of Bitcoin is still hard to figure. Is it the digital currency of the future, or a faddish bubble waiting to go pop? For most people, it’s difficult even to understand what Bitcoin is. There’s been no shortage of attempts to explain the crypto-currency in lay terms, but when presented with the question, “What do people want to know about Bitcoin?” very smart people come up with wildly divergent answers.

One of the simplest is a two-minute video on Vox, the new explanatory journalism website started by former Washington Post blogger Ezra Klein. Klein calls Bitcoin a "new kind of payment network, something like Visa or PayPal." But unlike those platforms, it has no headquarters, no rules, no set fees. This, he points out, is what makes Bitcoin both scary and potentially powerful, as much like a new Internet as a new kind of money. "You can do cool things without any central authority being able to tell you no," he says, citing international money transfers that are faster and cheaper than Western Union, and even new kinds of services currently impossible in traditional payment networks.


So, that's one explanation. It's easy to understand, in part because it glosses over the technical underpinnings of Bitcoin completely. But to other well-intentioned Bitcoin explainers, it's precisely the technical side of Bitcoin that's the real story. Richard Bondi, a Google employee and Cambridge resident, has written a 59-page explainer, posted to his personal website ( that suggests if you really want to understand why Bitcoin matters, you have to appreciate the ingenuity of how it works.

Banks keep track of accounts with a closely guarded ledger, listing who holds how much money. Bitcoin, he explains, is also based on a transaction ledger—known as the "blockchain"—but the ledger is public and shared. Everyone connected to the Bitcoin network has a copy. Bondi explains that Bitcoin creator Satoshi Nakamoto came up with "three grand ideas" to build an open system that people couldn't fraudulently alter.

First, he saw a way to deploy an existing security technique known as a cryptographic hash to link the entries in the ledger in an encoded chain, such that to modify a single entry you need to break a separate complex code for every entry—and that takes an impractical amount of time. Nakamoto's second and third "grand ideas" had to do with attracting people to Bitcoin in the first place, including the widely discussed practice of Bitcoin "mining"—which essentially delivers small rewards to users who put their computing power to work authenticating Bitcoin transactions.


This all gets complex quickly, and even the above version is radically simplified. But one cool outcome of diving into the Bitcoin protocol is that you begin to see why "currency of the future" might not be so far-fetched. Bondi notes that rather than buckling under its own weight, Bitcoin actually gets stronger as more people use it. "What's rather beautiful," he writes, "is that the more miners and transactions there are, the harder it is for an evil Eve to try to undermine the system....That's the opposite of a centralized system, which becomes weaker the more transactions and financial participants it has to coordinate."

Drink the fog

Fog is atmospheric, but a pain in most every practical sense—it makes it hard to fly or drive, and on a summer day, you can’t wait for it to burn off. A team of engineers at MIT, however, has found a way to put fog to good use: turn it into drinking water.

Detail above: Small drops grow from the corners; large drops block the open space in the mesh.courtesy of Gareth McKinley

"Fog represents a large, untapped source of potable water, especially in arid climates," MIT mechanical engineer Gareth McKinley wrote recently in the journal Langmuir. He and his colleagues, including MIT chemical engineer Robert Cohen, drew inspiration from the natural world, where insects like the Namib Desert beetle survive by collecting fog water on their wings. The researchers constructed a mesh square that stands upright in the air on poles; thanks to its weave and coatings applied to the fibers, they say, it's 500 percent more efficient at pulling water out of fog than previous contraptions. They worked with engineers at the University of Chile to deploy the prototype in the semi-arid Coquimbo Region of Chile, a place with little rain, but where fog regularly rolls in over the mountains. The technology has the potential to provide inexpensive access to drinking water to local residents, who may start hoping that foggy mornings turn into long foggy afternoons.


World War I, a slang guide

This spring, the British Library reissued “Lingo of No Man’s Land: A World War I Slang Dictionary.” Written by Lorenzo Smith, a Massachusetts native who joined up with Canadian troops in 1915, it was originally meant as a recruiting tool—a way to make the world of trench warfare intelligible to prospective soldiers. Today, it also provides a surprisingly intimate and full portrait of life at the front of the Great War.

the british library

"Dolly Varden" was the British term for a German helmet; "Tickler's Artillery" described homemade hand grenades fashioned from jam tins. "Flying Pig" was the term for "one of the heaviest trench mortars," which exploded with a concussive force so great that "a man's insides burst like a kernel of popcorn and death was usually instantaneous." There's humor in terms like "French Beer" ("Two percent beer, which the soldiers consider about as 'thrilling as the kiss of a man's sister'") and a grim sense of struggle in the definition of "Hun" ("The cruelest animal known. Will soon be extinct.")

In a brief foreword, Smith eloquently explained the connection between wartime conditions and the birth of new slang. The war exposed men to "sights and sounds inconceivable before August, 1914," he wrote. "It is no wonder that new words and new terms had to express our surroundings and experiences."

Kevin Hartnett is a writer in South Carolina. He can be reached at