Craig Wright, who has claimed he was the mysterious creator of bitcoin, has backed down on his promise to provide "extraordinary" evidence to support the claim.
In a blog post titled "I'm Sorry" the Australian computer scientist said he was "not strong enough for this".
"I believed I could do this. I believed I that I could put the years of anonymity and hiding behind me," he wrote. "But, as the events of this week unfolded and I prepared to publish the proof of access to the earliest keys, I broke. I do no have the courage. I cannot."
On April 2 Wright publicly stated that he was the founder of the cryptocurrency, who had previously only been known using the pseudonym Satoshi Nakamoto. In December 2015 WIRED US and other publications said it was likely Wright was Nakamoto.
Speaking to the BBC and the Economist this week, Wright said he created bitcoin. During research for the story Wright provided the organisations with digitally signed messages that supposedly contained cryptographic keys created during the initial stages of Bitcoin's development.
Wright's claims were supported by a core bitcoin developer, Gavin Andresen, who said that he believed Wright was Nakamoto. "I am very happy to be able to say I shook his hand and thanked him for giving Bitcoin to the world," Andresen said in a blog post.
However, since the publication of the story there have been severe criticisms of Wright's claims. One post on GitHub, by Patrick McKenzie, said it was possible to replicate the results that Wright had shown.
"I'm reasonably confident that I could have sold the same story, with approximately two hours of preparation," McKenzie said. "The non-experts did not ask to see things which would be hard for non-Satoshi to provide – they were at the mercy of the charlatan."
Following the criticisms Wright said it would be possible for him to prove, beyond doubt, that he was the creator. "I will present what I believe to be 'extraordinary proof' and ask only that it be independently validated. Ultimately, I can do no more than that."
Wright's most recent statement says that his inability to provide evidence will "cause great damage" to those who trusted him. While he does not admit to faking any of the evidence provided to the publications it does provide ammunition to those who speculated his claims were not true.
Trying to identify Nakamoto, who published bitcoin's code in 2009, has been a perilous business for those who have attempted to unravel the secretive persona.
In March 2014 Newsweek claimed to have uncovered "the face behind bitcoin," naming 65-year-old Dorian Nakamoto as the currency's source, but Nakamoto denied the link and had plans to sue the publication.
The bitcoin community also rejected the Newsweek story. Separately, in 2014, a hacker who claimed to have accessed an email address belonging to Nakamoto threatened to expose the real identity of the secretive creator.