Bitcoin is a decentralized digital currency, or cryptocurrency, based on a peer-to-peer network and can be exchanged through computers internationally without a financial intermediary. The system was first introduced by an unidentified programmer or group under the name of Satoshi Nakamoto in 2009.

The Winklevoss brothers have introduced the bitcoin index, or so-called Winkdex, which will also be used to price the value of assets held by the Winklevoss Bitcoin Trust. The proposed COIN ETF is designed to track a basket of shares tied to the digital currency, which has experienced volatile pricing.

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Bitcoin currently trades at around $639.5, or up 68.7% over the past year. Bitcoin started to gain widespread attention in late 2013 after surging above $1,100.

For more information on the cryptocurrency, visit our bitcoin category.