Bitcoin has begun trading on a major exchange for the first time in what is being regarded as step towards legitimising the digital currency.The Cboe Futures Exchange in Chicago opened trading in Bitcoin futures at 23:00 GMT on Sunday.After opening at $15,000, Bitcoin futures soon rose to $15,600 and then as high as $16,630.The Cboe move is expected to be followed next week by rival listing on the Chicago Mercantile Exchange.Anticipation of the first mainstream listings have helped the currency soar past $10,000 and then over $17,000 on Thursday before retreating. Bitcoin has been trading at about $15,350, according to Coindesk.com.Nick Colas, of Data Trek research, said the futures listings gives Bitcoin “legitimacy – it recognises that it’s an asset you can trade”.Futures are a type of derivative contract that allows trading based on movements in Bitcoin prices, without requiring ownership of the currency itself.The start of the Cboe market was expected to be low key, without the equivalent of a bell-ringing by representatives of a newly listed firm on the New York Stock Exchange, for example.There was “no champagne” planned, said a Cboe insider, who added: “It’s going to happen quietly – a switch flipping. There are not going to be many people in the office.”However, the exchange tweeted on Sunday to warn that its website was “performing slower than usual and may at times be temporarily unavailable” after trading started, but that all trading systems were operating normally. The Cboe and CME launches were made possible following approval by the US Commodities and Futures Trading Commission (CFTC).However, the regulator has warned investors about the “potentially high level of volatility and risk in trading these contracts”. Critics include CNBC financial commentator Jim Cramer, who argues that futures trading opens the door to “short sellers” that bet on downward moves in asset prices.Bitcoin is not regulated by any country’s central bank and has no universally recognised exchange rate.Cboe said trading will be suspended for two minutes if Bitcoin prices rise or fall by 10% in a bid to reduce wild fluctuations.”We are committed to continue to work closely with the CFTC to monitor trading and foster the growth of a transparent, liquid and fair Bitcoin futures market,” the Cboe said.The Futures Industry Association, which includes some of the world’s biggest derivatives brokerages, has criticised the CFTC’s decision, arguing that insufficient attention has been paid to the risks involved.