IV. Confrontation
El Salvador

I still did not have definitive proof of Satoshi’s identity. Only Satoshi himself could provide that, if he used a private key associated with one of Bitcoin’s first blocks. But I now had a wealth of evidence.

In mid-November, I wrote to Mr. Back to request another interview. This time, I didn’t beat around the bush. I wrote that I had concluded that he was Satoshi and I wanted to show him everything I had uncovered and give him a chance to address it. I even offered to fly to Malta. Once again, he didn’t reply.

So I decided to approach him in person at a Bitcoin conference where he was scheduled to speak in El Salvador two months later.

I landed in balmy San Salvador in late January with a plan. Mr. Back’s panel was on the conference’s second day. I would approach him then. But late on the afternoon of the first day, I noticed that he had posted photos of himself onstage at the conference on his X feed. Confused and worried I had missed my opportunity, I rushed to the speakers lounge, thinking I might find him there. But security guards denied me access, so I planted myself near the lounge entrance and kept my gaze fixed on the door.

Thirty minutes later, Mr. Back came out. I walked up to him, reintroduced myself and explained why I had come. He was slightly flustered but, to my pleasant surprise, he agreed to meet with me the next morning in the lobby of his hotel, which was doubling as the conference venue.

When I arrived at the appointed hour, Mr. Back was flanked by two executives from a new Bitcoin treasury company he had co-founded. He explained that the company was in the process of going public, forcing him to be more careful about how he interacted with the press.

I had completely missed this new development. Bitcoin treasury companies borrow money and use it to amass bitcoins, providing investors with a more aggressive way to bet on the cryptocurrency. Mr. Back had started his last summer and was merging it with a publicly traded shell created by Cantor Fitzgerald, the Wall Street firm formerly led by Commerce Secretary Howard Lutnick. As chief executive of the merged company, Mr. Back was required under U.S. securities law to disclose any information that was material to its investors. A secret stash of 1.1 million coins that could crash the Bitcoin market if it were suddenly sold, for example, would probably be considered material.

As I absorbed this new wrinkle, the four of us headed up to Mr. Back’s hotel room. Mr. Back looked tan and relaxed in a black T-shirt and black slacks.

Over the next two hours, I presented my evidence piece by piece. In his soft British lilt, Mr. Back insisted he wasn’t Satoshi and chalked it all up to a series of coincidences. But at times, his body language told a different story. His face reddened and he shifted uncomfortably in his seat when confronted with things that were harder to explain away.

For instance, Mr. Back didn’t have a good answer for why he disappeared from the Cryptography list during the period Satoshi was active, other than to say he was busy with work. Nor did he have a good answer for why he claimed on the “Let’s Talk Bitcoin” podcast that he had participated in the late 2008 list discussion sparked by Satoshi’s white paper, when he clearly hadn’t. When I pushed Mr. Back on both points, he turned defensive.

“Ultimately, it doesn’t prove anything. And I will reassure you, it’s really not me,” he said in a sharp tone.

When I brought up the results of our writing analyses, Mr. Back fumbled for an explanation but couldn’t find one.

“I don’t know,” he said. “It’s not me, but I take what you’re saying that this is what the A.I. said with the data. But it’s still not me.”

Mr. Back argued that it was hard to prove a negative. But he offered up one proof that he wasn’t Satoshi: the fact that he was so ignorant about Bitcoin when he first joined the #bitcoin-wizards IRC channel that he mistakenly thought a Bitcoin address functioned like a fluctuating bank balance. (A Bitcoin address is more like a physical wallet containing dollar bills; the change you get back from a transaction is made up of entirely new digital coins.)

The rub was that there was no trace of this misunderstanding in the channel’s logs. When I pointed this out to Mr. Back, he made light of it: “It would be hilarious if I hallucinated it.” (In a subsequent email, he said it might have happened in another IRC channel that wasn’t logged.)

Mr. Back denied being Satoshi more than a half-dozen times, but I found the phrasing of one of those denials — after I pointed out that he had outlined virtually every aspect of Bitcoin years before it was invented — revealing: “Clearly I’m not Satoshi, that’s my position.”

That sounded more like a rhetorical stance than a statement grounded in fact. But Mr. Back quickly caught himself and added: “And it’s true as well, for what it’s worth.”

Mr. Back did agree with me about some things. He acknowledged that he had the right background and skill set to be Satoshi. And he agreed that Satoshi was British, older than 50 and likely a member of the Cypherpunks. He also agreed with me about the inconsistency I’d noticed in the emails Satoshi had sent him: Satoshi would had to have known about b-money if he had read Mr. Back’s Hashcash paper, Mr. Back conceded.

But he denied that the emails were a ruse to divert suspicion from himself. This might have been more convincing if he had agreed to produce the emails’ metadata. However, he continued to ignore my request for it.

I still had a few things I wanted to confront Mr. Back with, but his aides said he had other meetings to attend. We took the elevator back down to the lobby and shook hands like two chess players after a hard-fought match.

As I watched Mr. Back disappear into the crowd of jovial conference goers, something nagged at me. For a fleeting moment, I thought I had heard him slip and say something as though he was Satoshi himself. But I couldn’t remember what it was.

When I got home to New York, I found it in the recording I’d made of the interview. It was when I was walking him through the similarities between things he and Satoshi had written. I brought up one of Satoshi’s quotes, but before I had a chance to explain why I was mentioning it, Mr. Back interrupted.

Me: There’s a quote that I mentioned earlier where Satoshi says, “I’m better with code than with words.”

Adam Back: I did a lot of talking though for somebody, I mean … I mean, I’m not saying I’m good with words but I sure did a lot of yakking on these lists actually.

To my ears, it sounded like he was saying that for someone who preferred code over words, he sure had written a lot of words. Implicit in that was an acknowledgment that he had been the one who wrote the quote. In other words, for a few seconds, Mr. Back had let the mask fall and turned into Satoshi.

I emailed him to confront him about it a few days later. He denied that it was a slip. “I was just responding conversationally to a general observation about technical people often feeling more comfortable expressing ideas in code than in prose,” he wrote.

But I had been crystal clear: I had asked about a specific Satoshi quote, and I suspected Mr. Back knew that.

I recalled how 10 years before, Satoshi had come out of hiding to help Mr. Back win the war over block size. And here Satoshi was, back again in a luxury hotel in El Salvador. Only this time, he had served Mr. Back less well because he’d removed any lingering doubt in my mind that I had the right man.

From the comments
545

John Carreyrou
Investigative reporter
The mystery of Satoshi Nakamoto had captivated me for a long time. Bitcoin was this thing that had materialized out of thin air, upended our financial landscape and spawned a $2.4 trillion industry. And yet, after 17 years, we still had no idea who had created it or what their motivations were. One of the most significant inventors of the past century was unknown. That didn’t seem right to me. Eighteen months ago, I decided enough was enough. I needed to know who this person was and I felt strongly that the public should too.

Produced by Aliza Aufrichtig, Molly Bedford, Rebecca Lieberman and Renee Melides.

Photo credits for headshots (from left to right): Yonhap/EPA, via Shutterstock, Amir Hamja for The New York Times, Joe Raedle/Getty Images.

John Carreyrou is an investigative reporter for The Times’s business section.

Dylan Freedman is the A.I. projects editor for The Times, investigating a range of topics. He has experience as both a reporter and a machine-learning engineer.