Bitcoin has been slowly fighting its way to mainstream respectability in the past year.
A summit on digital money in Downing Street last September and official recognition from the Federal Election Commission that US politicians can accept donations in the cryptocurrency are the fruits of tireless lobbying.
But not everyone in the bitcoin community is happy with this state of affairs. Amir Taaki, a bitcoin developer, says: "The whole point of bitcoin is that it's here now, it's working, we don't need to ask [for] anything."
Taaki, 26, is part of a faction fighting for the heart of bitcoin to remain in the anarchist cypherpunk community where it started, rather than complete its transformation into a professional, but ultimately neutered, digital currency.
"There's this attitude right now that bitcoin is just this investment, or a superior way to do payments, or something that's going to make it more efficient to do commerce," says Taaki. "It's the idea that bitcoin isn't something that's fundamentally different, but something reformative, to paper over the cracks in the system.
"A lot of people are asking regulators to give them regulation, and proactively censoring themselves to please people with power. It's unbelievable, people are afraid to say anything because of the perceived threat.
"Instead, we need to be bold with these things. There's a lot that's possible with bitcoin. There's a lot coming up."
DarkWallet is Taaki's way of being bold. At its heart, it's a bitcoin wallet, similar enough to the software he denigrates as being about "making it easy for grandma to use". But rather than focusing on ease of use, DarkWallet differentiates itself by amping up the features which made bitcoin so tempting to those trying to opt out of normal society.
"There's a certain group of bitcoin people, who always talk about it as a 'payments innovation'. They say we need to sacrifice some of our integrity to get the money in, and take this plaything away from the anarchists who invented it," Taaki says.
While payments made with bitcoin are far harder to trace back to an individual than those made with credit or debit cards, they aren't fully anonymous. Conventional bitcoin wallets open up the prospect of identification by looking at other payments made from the same wallet: for instance, a user who sends money to a known drug dealer with the same wallet they use to buy computer hardware from Overstock.com is easy to track down.
DarkWallet builds in functions that overcome that possibility. For instance, users can share "stealth" addresses, which let transactions occur between wallets known only to the sender and receiver. The secret address is shared cryptographically, ensuring that no third party can eavesdrop on the transaction.
Another feature lets users automatically "mix" transactions. When users make mixed payments simultaneously, the money gets put in a central pool, and then paid out to the receiving addresses from there, making it impossible to tell which user was paying which receiver.
And, once the software is made, it's nigh-on impossible to shut down. Like bitcoin itself, DarkWallet's special features are decentralised, meaning that there's no central server to take out, and no easy way to close off access to the network.
Naturally, such features can be used for nefarious ends too, but Taaki says that's the price to be paid for freedom. "There's a new future that's possible, but everyone's just worrying this thing will be used for paedophiles, or drugs, or crime. That's what liberty's about. My message is: step out in any direction you choose. There's so much more to this tool. The values are in it being uncensored – its privacy aspects. There are things deep down in bitcoin that we haven't yet explored."
But as well as enabling an unstoppable vision of anarcho-capitalism, Taaki argues that bitcoin and DarkWallet can create whole new forms of trade. One feature, built into bitcoin but only fully implemented in DarkWallet, allows for transactions which can only be finalised with consent from a set number of bitcoin users. "Imagine," says Taaki, "you can create a fund between 10,000 people and watch the hive mind decide how to use that money. It would be the world's first co-operative bank.
"Or say I want to start a business but don't have trust from the community. I can very publicly partner with someone who does, and make it so that I can only spend the firm's money with their permission. It's not always practical that you have to go through the legal system."
As for the risk of being shut down for enabling crime? Taaki isn't worried. "If the government want to try and close it down, that's a very odious act of censorship against people creating works of art. DarkWallet is art. When I write code, I encode my values, just like when someone makes art or music."
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