Australian businessman Craig Wright has backtracked on a promise to provide "extraordinary proof" he's the creator of bitcoin, stating in a blog post he no longer has the "courage" to do so.
Mr Wright, 45, told the BBC, The Economist and GQ on Monday he was Satoshi Nakamoto, the pseudonym used by the creator of the digital currency.
His declaration was widely questioned, with computer security experts labelling it a "scam" and The Economist calling on him to further substantiate his claim.
The Brisbane-born entrepreneur responded with a blog post on Tuesday, saying he would move some of the early bitcoin in the coming days to prove he is Mr Nakamoto.
"I will be posting a series of pieces that will lay the foundations for this extraordinary claim, which will include posting independently-verifiable documents and evidence addressing some of the false allegations that have been levelled," Mr Wright wrote.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"I will present what I believe to be "extraordinary proof" and ask only that it be independently validated."
But on Thursday a post on his blog reversed his position.
"I'm Sorry. I believed that I could do this. I believed that I could put the years of anonymity and hiding behind me," the post read.
"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 not have the courage. I cannot."
Mr Wright said his qualifications and character had been attacked and when those allegations were proven false, new allegations began.
"I know now that I am not strong enough for this."
Mr Wright said he hoped the "honour and credibility" of his supporters, particularly bitcoin consultant Jon Matonis and lead developer Gavin Andresen, would not be "irreparably tainted by my actions".
"They were not deceived, but I know that the world will never believe that now. I can only say I'm sorry. And goodbye."
Mr Nakamoto, who invented bitcoin in 2008, is estimated to be sitting on a fortune of up to $US450 million ($A601 million) worth of the currency.
