A single bitcoin is now worth $200, thanks to a little-known exchange in China that is suddenly pushing the digital currency to new heights.

The exchange, called BTC China, has been growing rapidly for the past few months as demand for bitcoins has surged. Today, BTC China accounts for just under 33 percent of trades. That's ahead of long-time bitcoin exchange Mt. Gox (23 percent) and another rival, the Slovenia-based BitStamp (25 percent). Mt. Gox has long been the most popular exchange – and the most well known – but it has now fallen behind not one but two rivals.

BTC China seems to be riding a speculative mini-bubble that has boosted bitcoins' value by more than a third since the federal government shut down the Silk Road online drug market, which accepted payments in bitcoin, about three weeks ago. On Tuesday, bitcoins crested over $200 for the first time since their wild runup last spring. That's about ¥1,220.

"There's been huge pickup in trading of bitcoins this year," says Bobby Lee, the CEO of BTC China. At one point, during the currency's last price surge last April, bitcoins were trading at the equivalent of $308 on his exchange, Lee says. That's about $50 above their peaks at other exchanges.

BTC China's trade volume has surged in the past month. Chart: Bitcoincharts.com

As you can see in this chart, BTC China has been surging since the Silk Road seizure, and it spiked even higher last week when news surfaced that China's search giant, Baidu, was now accepting bitcoins. Merchants on China's version of eBay – Alibaba's Taobao.com – are starting to accept bitcoins, but the price is really being driven by speculators, says Lee. "I think the Chinese really look to bitcoin as an excellent digital store of value, sort of like the new electronic version of gold," he says. "The Chinese like the idea of buying bitcoins to allow for deferred gratification from their savings."

Lee, a Stanford Computer Science graduate who once ran Yahoo Groups here in the U.S., took over as BTC China CEO in the spring, after leaving a job as VP of Technology with Walmart China. Apparently, he has crypto currency in his blood. His brother is Charlie Lee, the founder of Bitcoin's alternative, Litecoin.

BTC China was launched in June 2011 by Linke Yang – now head of marketing – and a technically adept partner who built the site's code. Fittingly, for a Bitcoin business, this partner wishes to remain anonymous. "He's been a little bit shy. He has preferred to not reveal his name publicly," says Lee.

Even within the bitcoin community, BTC China isn't well known name, says Dan Held, the co-Founder of Zeroblock, a bitcoin market data company. "It's just a really surprising runup," he says. "BTC China came out of nowhere."

But China is clearly interested in bitcoins. It's now the number-two source of downloads of the peer-to-peer client software that powers the bitcoin network.

To trade on BTC China, you need to have a bank account in China. So for the moment, the exchange is insulated from the U.S. regulatory problems that have caused Mt. Gox and other bitcoin businesses so much trouble. U.S. banks have been reluctant to do business with bitcoin companies, and that has made exchanging U.S. dollars for Bitcoins a tricky business.

In China, the regulatory environment is a "grey area," says Lee, but he expects things to eventually sort out. "We want to be legitimate and we want to be compliant with all laws."