Satoshi Nakamoto is the name used by the presumed pseudonymous person or persons who developed bitcoin, authored the bitcoin white paper, and created and deployed bitcoin's original reference implementation. As part of the implementation, Nakamoto also devised the first blockchain database. Nakamoto was active in the development of bitcoin until December 2010.

There has been widespread speculation about Nakamoto's true identity, with various people posited as the person or persons behind the name. Though Nakamoto's name is Japanese, and inscribed as a man living in Japan, most of the speculation has involved software and cryptography experts in the United States or Europe.

Nakamoto said that the work of writing bitcoin's code began in the second quarter of 2007. On 18 August 2008, he or a colleague registered the domain name bitcoin.org, and created a web site at that address. On 31 October, Nakamoto published a white paper on the cryptography mailing list at metzdowd.com describing a digital cryptocurrency, titled "Bitcoin: A Peer-to-Peer Electronic Cash System".

On 9 January 2009, Nakamoto released version 0.1 of the bitcoin software on SourceForge and launched the network by defining the genesis block of bitcoin (block number 0), which had a reward of 50 bitcoins. Embedded in the coinbase transaction of this block is the text: "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks", citing a headline in the UK newspaper The Times published on that date. This note has been interpreted as both a timestamp and a derisive comment on the alleged instability caused by fractional-reserve banking.

Nakamoto continued to collaborate with other developers on bitcoin's software until mid-2010, making all modifications to the source code himself. He then gave control of the source code repository and network alert key to Gavin Andresen, and transferred several related domains to various prominent members of the bitcoin community.

As of 2021, Nakamoto is estimated to own between 750,000 and 1,100,000 bitcoin. In November 2021, when bitcoin reached a value of over $68,000, his net worth would have been up to $73 billion, making him the 15th-richest person in the world at the time.

Nakamoto has never revealed personal information when discussing technical matters, but has at times commented on banking and fractional-reserve banking. Some speculated he was unlikely to be Japanese due to his native-level use of English.

On his P2P Foundation profile as of 2012, Nakamoto claimed to be a 37-year-old man who lived in Japan; he cited his date of birth as 5 April 1975. Some theorize that the date referenced the signing of Executive Order 6102, which prohibited the ownership of gold coins in the United States, and 1975 as the year it was repealed. Author Dominic Frisby categorized the date as an "obscure but brilliant reference" and as "extremely political".

Some have considered that Nakamoto might be a team of people. Dan Kaminsky, a security researcher who read bitcoin's code, said that Nakamoto was either a "team of people" or a "genius"; Laszlo Hanyecz, a developer who had emailed Nakamoto, had the feeling the code was too well-designed for one person; Andresen has said of Nakamoto's code: "He was a brilliant coder, but it was quirky."

The use of British English in both source code comments and forum postings, such as the expression "bloody hard", terms such as "flat" and "maths", and the spellings "grey" and "colour", led to speculation that Nakamoto, or at least one person in a consortium claiming to be him, was of Commonwealth origin. The reference to London's Times newspaper in the first bitcoin block suggested to some a particular interest in the British government.

Stefan Thomas, a Swiss software engineer and active community member, graphed the timestamps of each of Nakamoto's bitcoin forum posts (more than 500); the chart showed a steep decline to almost none between 5 a.m. and 11 a.m. Greenwich Mean Time (midnight to 6 a.m. Eastern Standard Time). This was between 2 p.m. and 8 p.m. Japan Standard Time, suggesting an unusual sleep pattern for someone living in Japan. As this pattern held even on Saturdays and Sundays, it suggested that Nakamoto was consistently asleep at this time.

Nakamoto's identity is unknown, but speculations have focussed on various cryptography and computer science experts, most of non-Japanese descent. Bitcoiners and cryptographers have suggested various methods by which a person could prove their identity as Nakamoto, such as moving the earliest bitcoins mined or signing a message with the key associated with the first bitcoins. On the other hand a denial of being Nakamoto is very difficult to confirm.

Hal Finney (4 May 1956 – 28 August 2014) was a pre-bitcoin cryptographic pioneer and the first person (other than Nakamoto himself) to use the software, file bug reports, and make improvements. He also lived a few blocks from a man named Dorian Satoshi Nakamoto, according to Forbes journalist Andy Greenberg. Greenberg asked the writing analysis consultancy Juola & Associates to compare a sample of Finney's writing to Nakamoto's, and found it to be the closest resemblance they had yet come across, including when compared to candidates suggested by Newsweek, Fast Company, The New Yorker, Ted Nelson, and Skye Grey. Greenberg theorized that Finney may have been a ghostwriter on Nakamoto's behalf, or that he simply used his neighbor's identity as a "drop" or "patsy whose personal information is used to hide online exploits"; but after meeting Finney, seeing the emails between him and Nakamoto and his bitcoin wallet's history (including the first transaction from Nakamoto to him, which he forgot to pay back) and hearing his denial, Greenberg concluded that Finney was telling the truth. Juola & Associates also found that Nakamoto's emails to Finney more closely resemble Nakamoto's other writings than Finney's do. Finney's fellow extropian and sometime co-blogger Robin Hanson assigned a subjective probability of "at least" 15% that "Hal was more involved than he's said" before further evidence suggested that was not the case.

In a high-profile March 2014 article in Newsweek, journalist Leah McGrath Goodman identified Dorian Prentice Satoshi Nakamoto, a Japanese-American man living in California, whose birth name is Satoshi Nakamoto, as the Nakamoto in question. Besides his name, Goodman pointed to a number of facts that circumstantially suggested he was the bitcoin inventor. Trained as a physicist at California State Polytechnic University, Pomona, Nakamoto worked as a systems engineer on classified defense projects and computer engineer for technology and financial information services companies. According to his daughter, Nakamoto was laid off twice in the early 1990s, turned libertarian, and encouraged her to start her own business "not under the government's thumb". The article's seemingly biggest piece of evidence was that when Goodman asked him about bitcoin during a brief in-person interview, Nakamoto seemed to confirm his identity as its founder, saying: "I am no longer involved in that and I cannot discuss it. It's been turned over to other people. They are in charge of it now. I no longer have any connection."

The article's publication led to a flurry of media interest, including reporters camping out near Nakamoto's house and chasing him by car when he drove to an interview. Later that day, the pseudonymous Nakamoto's P2P Foundation account posted its first message in five years: "I am not Dorian Nakamoto." In a subsequent interview, Nakamoto denied all connection to bitcoin, saying he had never heard of it before and that he had misinterpreted Goodman's question as about his previous work for military contractors, much of which was classified. In a Reddit "ask-me-anything" interview, he said he had misinterpreted Goodman's question as related to his work for Citibank. In September, the P2P Foundation account posted another message saying it had been hacked, raising questions over the authenticity of the message six months earlier.

In December 2013, blogger Skye Grey linked Nick Szabo to the bitcoin white paper using stylometric analysis. Szabo is a decentralized currency enthusiast and published a paper on "bit gold", one of bitcoin's precursors. He is known to have been interested in using pseudonyms in the 1990s. In a May 2011 article, Szabo said of bitcoin's creator: "Myself, Wei Dai, and Hal Finney were the only people I know of who liked the idea (or in Dai's case his related idea) enough to pursue it to any significant extent until Nakamoto (assuming Nakamoto is not really Finney or Dai)."

Financial author Dominic Frisby provides much circumstantial evidence but, as he admits, no proof that Nakamoto is Szabo. Szabo has denied being Nakamoto. In a July 2014 email to Frisby, he wrote: "Thanks for letting me know. I'm afraid you got it wrong doxing me as Satoshi, but I'm used to it." Nathaniel Popper wrote in The New York Times that "the most convincing evidence pointed to a reclusive American man of Hungarian descent named Nick Szabo."

On 8 December 2015, Wired wrote that Craig Steven Wright, an Australian academic, "either invented bitcoin or is a brilliant hoaxer who very badly wants us to believe he did". Wright took down his Twitter account and neither he nor his ex-wife responded to press inquiries. The same day, Gizmodo published a story with evidence supposedly obtained by a hacker who broke into Wright's email accounts, claiming that Satoshi Nakamoto was a joint pseudonym for Wright and computer forensics analyst Dave Kleiman, who died in 2013. Wright's claim was supported by Andresen and former Bitcoin Foundation director Jon Matonis.

Wright has said that he chose the name "Nakamoto" in honor of Japanese philosopher Tominaga Nakamoto, whom Wright learned about from his Japanese martial arts instructor, and "Satoshi" after the Pokémon character Satoshi, because his name was anglicized as "Ash", and thus "Satoshi" represents the current financial system that must be burned into ash to make way for cryptocurrency.

Many prominent bitcoin promoters remained unconvinced by the reports. Subsequent reports also raised the possibility that the evidence provided was an elaborate hoax, which Wired acknowledged "cast doubt" on its suggestion that Wright was Nakamoto. Bitcoin developer Peter Todd said that Wright's blog post, which appeared to contain cryptographic proof, actually contained nothing of the sort. Bitcoin developer Jeff Garzik agreed that the evidence Wright publicly provided proves nothing, and security researcher Dan Kaminsky concluded Wright's claim was "intentional scammery".

In May 2019, Wright started using English libel law to sue people who denied he was bitcoin's inventor and called him a fraud. In 2019, Wright registered US copyright for the bitcoin white paper and the code for bitcoin 0.1. Wright's team claimed this was "government agency recognition of Craig Wright as Satoshi Nakamoto"; the United States Copyright Office issued a press release clarifying that this was not the case (as they primarily determine whether a work is eligible for copyright, and do not investigate legal ownership, which, if disputed, is determined by the courts).

In March 2024, in the Crypto Open Patents Association (COPA) case before the High Court, Judge James Mellor ruled that Wright was not Satoshi Nakamoto.

First, that Dr. Wright is not the author of the Bitcoin white paper. Second, Dr. Wright is not the person who adopted or operated under the pseudonym Satoshi Nakamoto in the period 2008 to 2011. Third, Dr. Wright is not the person who created the Bitcoin system. And, fourth, he is not the author of the initial versions of the Bitcoin software.

— Judge James Mellor UK High Court 2024

The written judgment released on 20 May stated that documents submitted as evidence substantiate Wright's claim to be Satoshi were forgeries, and Dr Wright had "lied to the court extensively and repeatedly".

In a 2011 article in The New Yorker, Joshua Davis claimed to have narrowed down Nakamoto's identity to a few people, including the Finnish economic sociologist Vili Lehdonvirta and Irish student Michael Clear, who, in 2008, was an undergraduate student in cryptography at Trinity College Dublin. Each of them strongly denied being Nakamoto.

In October 2011, writing for Fast Company, investigative journalist Adam Penenberg cited circumstantial evidence suggesting Neal King, Vladimir Oksman and Charles Bry could be Nakamoto. They jointly filed a patent application that contained the phrase "computationally impractical to reverse" in 2008, which was also used in the bitcoin white paper by Nakamoto. The domain name bitcoin.org was registered three days after the patent was filed. All three men denied being Nakamoto when contacted by Penenberg.

In May 2013, Ted Nelson speculated that Nakamoto was Japanese mathematician Shinichi Mochizuki. Later, an article was published in The Age newspaper that claimed that Mochizuki denied these speculations, but without attributing a source for the denial.

A 2013 article in Vice listed Gavin Andresen, Jed McCaleb, or a government agency as possible candidates to be Nakamoto.

In 2013, two Israeli mathematicians, Dorit Ron and Adi Shamir, published a paper claiming a link between Nakamoto and Ross Ulbricht. The two based their suspicion on an analysis of the network of bitcoin transactions, but later retracted their claim.

In 2016, the Financial Times said that Nakamoto might have been a group of people, mentioning Hal Finney, Nick Szabo and Adam Back as potential members. In 2020, the YouTube channel Barely Sociable claimed that Adam Back, inventor of bitcoin predecessor Hashcash, is Nakamoto. Back subsequently denied this. Charles Hoskinson, founder of Cardano and co-founder of Ethereum, has also opined that Adam Back is the most likely candidate for Nakamoto.

Elon Musk denied he was Nakamoto in a tweet on 28 November 2017, responding to speculation the previous week in a Medium post by a former SpaceX intern.

In 2019, journalist Evan Ratliff claimed drug dealer Paul Le Roux could be Nakamoto.

In 2021, developer Evan Hatch proposed cypherpunk Len Sassaman of COSIC as a possible candidate. Sassaman had been mentioned on bitcointalk on 15 March 2013 when a user suggested Sassaman was Satoshi. A presentation given by Kaminsky at the 2011 Black Hat Briefings revealed that a testimonial in honor of Sassaman had been permanently embedded into bitcoin's blockchain.

In 2024, an HBO documentary directed by Cullen Hoback titled Money Electric: The Bitcoin Mystery named former Bitcoin developer Peter Todd as allegedly being Satoshi Nakamoto. Hoback's claim relies on a chat message written by Todd where he commented on a technicality in one of Satoshi's last posts, shortly after Todd had created his personal account, and just an hour after the initial post was made. Hoback also notes Nakamoto's use of Canadian English, as well as a subsequent chat post by Todd where he rued being, "the world's leading expert on how to sacrifice your bitcoins [...] I've done one such sacrifice and I did it by hand." Hoback characterized the latter as an admission by Todd of having destroyed access to the Bitcoin believed to be held by Nakamoto. In the film, Todd denied that he was Nakamoto, stating that it was "ludicrous" and "grasping at straws", and criticized Hoback by saying that it was "ironic that a director who is also known for a documentary on QAnon has resorted to QAnon style coincidence-based conspiracy thinking here too".

A bust of Satoshi Nakamoto was installed in Budapest, Hungary in 2021.

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