Mark Karpelès

Mark Karpelès was born in 1985 on the outskirts of the eastern French city of Dijon; he spent some time in Israel and settled in Tokyo, Japan, in 2009.⁠[1][2][1]

In 2011, Karpelès acquired Mt. Gox from American programmer Jed McCaleb; Magical Tux, the pseudonym he used on online forums, is also his Twitter and GitHub handle. According to a leaked Mt. Gox business plan, he owned 88% of the company. He rewrote the site’s back-end software and built Mt. Gox into the world’s most popular bitcoin exchange.⁠[2][3][2][2]

He contributed 5,000 bitcoins to help start the nonprofit Bitcoin Foundation and served on its board, a position he later resigned.⁠[2]

In February 2014, Mt. Gox shut its website and filed for bankruptcy protection in Tokyo. Karpelès bowed and apologized at a news conference, saying the company’s system had weaknesses, its bitcoins had vanished, and it had caused trouble for many people. In April that year, a US court demanded that he testify in Washington about the exchange’s collapse; through his lawyers he declined to appear, and at the time he had not been charged with any crime.⁠[4][2][5][5]

On August 1, 2015, Japanese police arrested Karpelès on suspicion of accessing the exchange’s computer system to falsify data on its outstanding balance; authorities then issued a new arrest warrant on embezzlement charges and extended his detention. In September 2015, he was charged in Japan with embezzlement and falsifying data; authorities suspected him of taking about $2.6 million worth of customers’ bitcoins, which he denied.⁠[6][6][1][1][1][1]

In April 2018, while still on trial in Tokyo, Karpelès became chief technology officer of the VPN service London Trust Media, whose cofounder and chairman, Andrew Lee, had briefly run Mt. Gox’s US operations.⁠[7][7][7]

Tokyo prosecutors charged Karpelès with offenses including embezzlement (of about 340 million yen) and aggravated breach of trust and sought a ten-year sentence; he pleaded not guilty and blamed a hack for the loss of Mt. Gox users’ bitcoins. On March 15, 2019, the Tokyo District Court acquitted him of embezzlement and aggravated breach of trust but convicted him of falsifying electronic records, finding that he illegally altered Mt. Gox’s electronic records to inflate the company’s holdings by $33.5 million; he was sentenced to two and a half years in prison, suspended for four years, and ordered to pay part of the trial costs.⁠[8][9][8][8][8][8][8]

Karpelès said he was happy to be found not guilty of embezzlement and breach of trust. Prosecutors subsequently dropped their appeal of the acquittals, while he appealed his conviction for falsifying records on the grounds that the judge had not fully considered the defense’s arguments; his lawyer Nobuyasu Ogata said his actions after the 2014 events were an effort to reduce risks for Mt. Gox users.⁠[8][10][10][10]

On June 5, 2019, Karpelès said at the Foreign Correspondents’ Club of Japan that he would become chief technology officer of Tristan Technologies, a Tokyo blockchain technology company planning to design a new, secure blockchain-powered operating system. He said his love for Japan had not changed and that he did not hold any cryptocurrencies because they carry high risks.⁠[9][9][9][9][9]

Former Mt. Gox user Gregory Greene sued Karpelès in federal court in Chicago in 2014. On January 8, 2020, Karpelès moved for summary judgment on three claims: conversion, negligence, and consumer fraud. In June 2021, Judge Gary Feinerman of the US District Court for the Northern District of Illinois rejected class certification for the $400 million suit for the second time, finding that determining how each of more than 30,000 users understood and relied on the terms of service would require “over 30,000 mini-trials”; Karpelès had argued that a compensation plan in Japan would serve better than litigation in the United States.⁠[11][11][11][12][12][12][12]

On June 11, 2020, Judge Mariko Goto rejected Karpelès’ appeal against his conviction for tampering with financial data and upheld the ruling, finding that his actions went against the terms of service that the company had indicated as its own will. The next day, Karpelès said the verdict relied on the prosecution’s concept that a company has its own “will” that can differ from that of management and shareholders, which he said could set a dangerous precedent; he had not yet decided whether to appeal again.⁠[13][13][13][13][14]

In September 2024, during Korea Blockchain Week, Karpelès said he would launch the crypto-asset exchange EllipX in Poland, initially crypto-only and serving European users, with plans to comply with the EU’s Markets in Crypto-Assets Regulation (MiCA) and undergo regular third-party audits; former Mt. Gox users could get at least 50% off trading fees through non-fungible tokens he had previously issued. He said he had received death threats after the hack but that the crypto community’s attitude toward him had softened in recent years.⁠[15][15][15][15][15][15]

Speaking at the Foreign Correspondents’ Club of Japan on October 11, 2024, as CEO of Karpeles Lab, he said it was very difficult to create a crypto exchange in Japan and that, according to people in the industry, most Japanese crypto exchanges were losing money because of regulation.⁠[16][16][16]

In February 2026, Karpelès submitted a Bitcoin consensus rule proposal on GitHub that would allow the 79,956 bitcoins stolen from Mt. Gox and held in a single wallet to be moved to a recovery address without the original private key, for distribution to creditors by the Mt. Gox trustee under the existing procedures. He acknowledged that it was a hard fork requiring all nodes to upgrade before the activation height and said the proposal was meant to start a community discussion and break the deadlock between the trustee and the community. The proposal met strong opposition on the Bitcointalk forum.⁠[17][17][17][17]

On October 9, 2026, after Ledger said it was investigating fund losses among customers of the Southeast Asian reseller CryptoBilis, Karpelès said on X that this could be exactly what he had been investigating and asked those affected to contact him or open their Ledger devices and send photos to confirm whether they contained a “spy implant.” He said implanted devices pass Ledger’s genuine check and that the only way to detect the implant is to open the device. He also asked CryptoBilis to open some of its unsold Ledger wallets so their circuit boards could be inspected for spy implants or other unauthorized modifications.⁠[18][19][20]

As he described in a series of posts, an extra chip inside the casing reads what appears on the screen, records the recovery phrase when the device displays it for the user to write down, and transmits it, while the genuine secure element works normally; earlier versions of the implant gave themselves away with sloppy shrink wrap, whereas the new one is far better made and hidden under the display, the most obvious tell being an antenna cable that looks clearly out of place. His own test device had aroused his suspicion because it was listed on Amazon at half price and shipped from Malaysia rather than Japan, where he had ordered it. At the time, there was no confirmed evidence that the thefts were caused by hardware implants.⁠[21][21][21][21][20]

On October 13, 2026, Karpelès said a Ledger Flex bought at Singapore airport had been confirmed to contain a spy implant; its buyer had noticed suspicious marks on the casing and sent it to him rather than using it. He published a video about it on YouTubeYouTubeYouTube is Google’s video-sharing and creator platform, founded in 2005 by Steve Chen, Chad Hurley, and Jawed Karim and acquired by Google in 2006. Built around video uploading, viewing, and creator earnings, the platform has developed Shorts, YouTube Music, Premium, YouTube TV, and products for children, and is headquartered in San Bruno, California, United States.Open the full entry.⁠[22][22][23]

In October 2026, Karpelès told CointelegraphCointelegraphCointelegraph is a digital news outlet covering blockchain, digital assets, artificial intelligence, and fintech, known for its cartoon-style news illustrations. It also runs businesses including Cointelegraph Magazine, research, an accelerator, and events.Open the full entry that, to his knowledge, at least two people had reported tampered devices to Ledger since December 2025, but he had not seen Ledger issue any public warning; he said that while not responding to a single implant found in a device bought from a shady dealer might be normal, the growing number of reports and increasingly sophisticated technology should have prompted Ledger to act, at least by reminding customers to be careful. Ledger confirmed that one affected device contained an unauthorized implant and declined to comment on its handling of an earlier disclosure by security researcher Joe Grand.⁠[24][24][24][24][24]

X: Public account: https://x.com/MagicalTux (opens in a new window)⁠[3][18]

YouTube: Public channel: https://www.youtube.com/@MagicalTux (opens in a new window)⁠[23]