Bitcoin turned money into something completely virtual. Using a worldwide network of machines and the power of pure mathematics, it put currency in the hands of computer programmers, free from the rules and regulations of big government and big banks. But J. Chris Anderson wants to do something even more radical.

Anderson is starting a new digital currency project tentatively dubbed Document Coin. It's a bit of an odd duck, but it's intriguing, and Anderson is worth listening to. He's the co-founder and chief software architect of Couchbase, a kind of new-age database with some serious cred among Silicon Valley developers.

Instead of using pure mathematics to prevent things like the same person spending the same money twice, Document Coin will rely on personal reputation to keep all transactions in order. And each unit of currency created using Document Coin could have different values in different situations. If you use a coin in one place, it might be worth more than if you use it in another. The goal, Anderson says, is to get people to completely rethink the entire idea of money.

>Unlike with bitcoin, anyone will be able to create a new Document Coin anytime they want.

Unlike with bitcoin—which keeps its currency scarce by rewarding it only to those who participate in what amounts to a race to solve complex cryptographic puzzles—anyone will be able to create a new Document Coin anytime they want. The value of each coin will be completely subjective, depending on who creates the coin and why. "For example, the coin my disco singer friend created and gave me at my barbeque might be what gets me past the rope at the club," Anderson says. A coin minted by tech pundit Tim O'Reilly might be highly prized in Silicon Valley circles, but of little interest to musicians. "It's a bit like a combination of a social network with baseball trading."

Ultimately, he hopes to get developers thinking about the social implications of crypto-currencies, and to get people to question the idea that everything needs to have a set, numeric value. "If bitcoin is the toy version of what we'll all be using the future, then I want to build the crazy art project version of the future," he says. Document Coin's usefulness as a real currency is limited, but Anderson does hope people will eventually want to use it. "If you build something, you don't want to be disappointed if it succeeds," he says. "You need to build things that you would be happy to see take off."

To that, end, Anderson is working on getting the technology right. The idea is that each new Document Coin will be a cryptographically unique token that contains two parts: a set of encrypted data that only the owner of the coin can see, and a set of public data about the coin. "I could show you that I have a Tim O'Reilly coin without showing you exactly which one," he says.

>'If bitcoin is the toy version of what we'll all be using the future, then I want to build the crazy art project version of the future.'

To transfer a coin, a copy of the original would be created, but with new cryptographic keys so that only the new owner has access to it. That means it would be possible for someone to archive a copy of a coin that had already been spent and then try to spend it again later. But all the coins you spend will be associated with your public key, so if you double spend a coin, it could end up damaging the value that people place on all the coins you've issued, or plan to spend.

He hasn't released any code yet, but Anderson is building a prototype using Couchbase, but he's quick to say it's not an official company project. It's a personal endeavor. That said, Anderson does plan to add a set of new cryptography features that's he's developing for Document Coin back into the Couchbase open source project, which could eventually enable other developers to add security features to their own applications more easily. That's one potential benefit of Anderson's Document Coin efforts, even if the project doesn't end up becoming the next big thing.

If it does take off, it will probably start small. It's not hard to picture groups of friends using it to create custom coins based on inside jokes. Anderson says there would actually be a big benefit in the system being used in this way, since it would get people to create and maintain public encryption keys, setting the stage for more interesting uses later on. "Everything has to start out as a joke these days," he says. "Otherwise people won't take them seriously."