Craig Wright, the Australian computer scientist who claimed to be Satoshi Nakamoto -- the creator of bitcoin -- has backtracked on a pledge to provide more proof of his earlier claims. Wright says that he lacks the courage to face allegations. On May 1, Wright claimed that he was the creator of bitcoin, offering digital signature, signed using a private key that was thought to be held by Nakamoto. We later learned that the "proof" Wright offered was simply copied from an older transaction. At the time, Wright assured that he will be moving early bitcoins as "extraordinary evidence". On Thursday, Wright wrote in a blog post that he is "sorry," and that he cannot do this. He writes: 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.