Japanese police have arrested the CEO of the failed company MtGox, which was once the world's biggest exchange of the virtual currency, bitcoin.Mark Karpeles, 30, is being held in connection with the loss of bitcoins worth $387m (£247m, €351m) last February.He is suspected of having accessed the exchange's computer system to falsify data on its outstanding balance.MtGox claimed it was caused by a bug but it later filed for bankruptcy.Japan's Kyodo News said a lawyer acting on Mr Karpeles' behalf denied his client had done anything illegal.Mr Karpeles, who was born in France, is suspected of benefiting to the tune of $1m (£640,000), the agency said.In March 2014, a month after filing for bankruptcy, MtGox said it had found 200,000 lost bitcoins.The firm said it found the bitcoins - worth around $116m - in an old digital wallet from 2011.That brings the total number of bitcoins the firm lost down to 650,000 from 850,000.That total amounts to about 7% of all the bitcoins in existence.Bitcoin is a virtual currency built around a complicated cryptographic protocol and a global network of computers that oversees and verifies which coins have been spent by whom.

Australian police have raided the Sydney home and office of a man named by technology websites as the creator of the virtual currency Bitcoin.Federal police searched Craig Steven Wright's properties, but said the raid was about tax, not Bitcoin.Mr Wright was named by Wired and Gizmodo as the creator of Bitcoin.The founder of the currency is believed to hold about a million Bitcoins, which are reportedly worth about $400m at the current exchange rate.The raid in Sydney came hours after Wired and Gizmodo claimed Mr Wright was probably the mysterious "Satoshi Nakamoto", a pseudonym used by Bitcoin's creator.Their investigations were based on leaked emails, documents and web archives, including what was said to be a transcript of a meeting between Wright, a 44-year-old academic, and Australian tax officials.The 'Lord Lucan' of the digital worldMr Wright is reported to have said: "I did my best to try and hide the fact that I've been running Bitcoin since 2009.By the end of this I think half the world is going to bloody know."Journalists

and Bitcoin enthusiasts have long tried to find out who created Bitcoin.Last year, Newsweek claimed Satoshi Nakamoto was a 64-year-old Japanese-American living near Los Angeles.Mr Nakamoto, whose birth name was Satoshi, sued the magazine over the disruption he suffered as a result of the story.A London-based software developer and "hacker" has said he is under police investigation after going to Syria to fight against the Islamic State group.Amir Taaki, 29, a leading developer of online currency Bitcoin, was once named by Forbes as one of the most influential young people in technology.Mr Taaki told the BBC he returned to the UK from Syria in 2016 and has spent the past 12 months on police bail.The Foreign Office warns people not to travel to Syria for any reason."WhenI discovered Rojava [the term Kurds use to refer to northern or Syrian Kurdistan] I felt I had to go there," he told the BBC."At first, I was completely scared - I thought I was going to die."Igot sent to the frontline.I had no training, and I was given a Kalashnikov.

I learnt how to use a gun on the way, another Western fighter showed me."Mr Taaki says he spent three and half months fighting with the Kurdish People's Protection Units [YPG] military group and experienced several battles against IS.He says he was not injured in the fighting, except in one incident, he tells me laughing: "I did fall into a trench."Whenbitcoin atm mitasked "Did you kill anyone?"ethereum sslhe explains that his experiences in battles with IS were at long range, so it is impossible to tell."Itrusted bitcoin wallet in indiafound myself on the front with a gun, I had to fight.bitcoin las vegas conferenceBut I wanted to go elsewhere, where my skills would be useful."Mrbitcoin uri

Taaki says he later met with the economics committee of Rojava and began helping the Kurds with local projects, such as a crowd-funding campaign which raised money and then built fertilizer factories to help farmers growing food.The Syrian Kurds are not only fighting to defeat IS, but they have the aim of creating a new kind of socialist society.ethereum gtx 1060This Kurdish vision is based on revolutionary ideas of living in a much less hierarchical way than the West - a system called "democratic confederalism".This is what Amir Taaki says truly inspired him to travel to the conflict."Mymain goal with going to Rojava was not because I opposed Isis, it's because I support their [the Kurds'] revolution.I support their politics and their struggle."It is the only solution for lasting peace in the Middle East."Bitcoin,he believes, could help the Syrian Kurds."They'retrying to create a people's economy.To establish a decentralised economy, you need decentralised money.

"Rojava's under embargo, so there's no way to move money in or out.So we have to actually create our own Bitcoin economies."Nowwe have a technological tool for people to freely organise outside state system.Because it is a currency not controlled by central banks."But software previously developed by Amir Taaki to allow untraceable, anonymous transactions, has been criticised by authorities because it may be used for money laundering or to fund organised terror groups.When he returned to London in 2016, Mr Taaki says he was arrested at the airport and questioned under counter-terror legislation."Iwas not expecting it at all," he says."Theystopped the plane, and they arrested me.They confiscated computers, phones and everything".He says he has been told by police that he remains under investigation."Idon't support terrorism or terrorist acts.What's the political motive in keeping an investigation open against me?"There are no reliable figures for how many British people have gone to fight with the Kurds.

The YPG itself estimates that "hundreds" of volunteers from many countries have fought with it.The YPG is not a banned group in the UK, but is considered a terror organisation by Turkey, which has a history of conflict with the Kurds.Mr Taaki was once tipped to be a future billionaire.He could work in Sillicon Valley and enjoy an incredible career.So why not, I ask?"I could go and live on a beach in Brazil and party," he tells me."I don't want that, though."Whenchallenged on why he needed to pick up a gun at all, he replies: "I'm glad about it, to be honest, it was an important experience to have."AMetropolitan Police spokesman said: "Everyone who returns from taking part in the conflict in Syria or Iraq must expect to be reviewed by the police to determine if they have committed criminal offences and to ensure that they do not pose a threat to our national security."Watcha special piece with Amir Taaki on the Victoria Derbyshire Show on BBC1 on Thursday at 9am.The Daily Politics programme will discuss the government's stance on fighting in Syria on BBC2 on Friday at noon.