Craig Steven Wright, the man claiming to be mysterious Bitcoin founder Satoshi Nakamoto, is abruptly withdrawing from public life. Wright posted today that he would offer no more evidence to prove his identity, just days after he publicly claimed the Satoshi mantle in a series of coordinated articles. Wright's claims were greeted with intense skepticism from many in the Bitcoin community, who saw Wright as a con man using the Satoshi identity for personal gain. Wright had a number of prominent supporters within the Bitcoin community, including Jon Matonis and Gavin Andresen, both of whom maintain unequivocally that Wright truly is Satoshi.

As recently as yesterday, Wright had promised new evidence that would definitively prove his identity as Bitcoin's creator, writing that "extraordinary claims require extraordinary proof." In particular, Wright had pledged to transfer funds from one of Bitcoin's early blocks. While not definitive proof, that demonstration would have been by far the strongest evidence ever provided about Satoshi's true identity.

But according to the latest message published on his personal site, Wright abruptly lost the courage to carry through with the demonstration, fearing it would lead to personal attacks against him. The message is reproduced in full below:

I’m Sorry.
I believed that I could do this. I believed that I could put the years of anonymity and hiding behind me. 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.
When the rumors began, my qualifications and character were attacked. When those allegations were proven false, new allegations have already begun. I know now that I am not strong enough for this.
I know that this weakness will cause great damage to those that have supported me, and particularly to Jon Matonis and Gavin Andresen. I can only hope that their honour and credibility is not 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.In broad strokes, there's reason to be sympathetic with Wright's case. He appeared on the public stage against his will in December, after leaked emails pointed to him as a possible Satoshi. The result was a new and apparently unwanted level of attention to his past business ventures, which showed plenty of irregularities but no hard evidence of anything more nefarious than tax problems. As Wright says, his qualifications and character really have been attacked, and there's no reason to think that would stop if he produced better evidence that he is, in fact, Satoshi.

But in the past week, Wright has given us more reason than ever to doubt him. His early public demonstration looked like proof at first glance, but closer inspection revealed a duped signature string that seems to have been inserted as a deliberate attempt to mislead. Similar research turned up a set of backdated PGP keys after the first round of claims in December. At each stage, the evidence pointing to Wright as Satoshi has contained specific and deliberate falsifications. Now that Wright has publicly claimed to be Satoshi, it's entirely plausible that he falsified that evidence himself.

Throughout all of it, there have been a number of simple, concrete actions Wright could have taken to prove his ostensible identity: signing the genesis block, signing a message with Satoshi's PGP key, or making a transaction with one of the many bitcoin blocks linked to Satoshi. Wright has now disappeared without taking any of those steps, but generating as much attention as possible along the way. For skeptics, that behavior is exactly what you'd expect — and for those who believe him, it's harder than ever to explain.