Dr Adam Back
In his first witness statement, Dr Back described and exhibited his brief email exchanges with Satoshi Nakamoto in August 2008 and later in January 2009. He said these emails had never previously been published (as related above at [23.2]). These emails do not show Dr Back being dismissive at all.
In his second witness statement, Dr Back responded to the parts of Wright1 in which he had been mentioned. His evidence shows the following:
That Dr Wright’s claim to have been profoundly influenced by Wei Dai’s b-money proposal was a lie, since Satoshi’s first email to Dr Back shows that Satoshi was not previously aware of that proposal, a point confirmed by Wei Dai (see above).
That Dr Wright’s claim that Dr Back was dismissive and had said that digital cash had been attempted before and was bound to fail, was a lie. Far from being dismissive, Dr Back points out he was one of the applied researchers who continued to work on making p2p electronic cash a reality, after the failure of Digicash in 1998. He also said that Hashcash was a building block used by others in their designs, including Wei Dai in 1998, Nick Szabo in 1998 and Hal Finney in 2004.
In addition, Dr Back responded to Dr Wright’s claim in [94] of Wright1 that Bitcoin uses an algorithm derived from Tuomas Aura’s 2000 paper and not Hashcash. Dr Back gave a series of detailed chronological and other reasons why he did not think this was correct, not least the fact that his Hashcash paper is cited in the Bitcoin White Paper (reference [6]), but there is no reference at all to the paper by Aura et al. Dr Back also stated that the proposals in his Hashcash paper and that of Aura et al are different in that Aura’s work is about an interactive client-server protocol, while Hashcash is a non-interactive proof. He pointed out that Bitcoin, being peer-to-peer, necessarily cannot involve a server. In this regard, it is relevant to note that Satoshi actually wrote, in the Bitcoin White Paper, ‘we will need to use a proof-of-work system similar to Adam Back’s Hashcash [6],’ and made no mention of Aura.
Professor Meiklejohn addressed proof-of-work systems in her first report at [62]-[63], making the point that proof-of-work is not unique to Bitcoin. In respect of Bitcoin, she made the straightforward point that the specific type of proof-of-work used in Bitcoin is derived from a previous proposal called Hashcash, as proposed by Adam Back in 2002, as referred to in the Bitcoin White Paper.
Dr Wright then responded in Wright11. In Wright11 at [387], Dr Wright responded to Dr Back’s mention that Satoshi cited his Hashcash paper in the Bitcoin White Paper with this statement: ‘I did so because I mentioned it in the White Paper, not because I used the algorithm’, an explanation which I consider to be bizarre, given what Satoshi actually wrote. Dr Wright went on to refer to the algorithm used in Hashcash as being different from that implemented in Bitcoin, on the basis that ‘the algorithm does not use a series of leading zeros as Bitcoin implements.’
Similarly, later in Wright11, Dr Wright sought to respond to Professor Meiklejohn’s first report at [62]-[63] and the first and second witness statements of Dr Back, saying:
‘I will note that the initial Hashcash scheme and the Bitcoin Proof of Work (PoW) mechanism differ in their core concept and the specifics of their implementation,
particularly in how the target for hash collision is defined.’
In [601] he sought to summarise how he saw the differences. Under the sub-heading of ‘Bitcoins’s Proof of Work’ he said this:
‘e. Target with Leading Zeros: In Bitcoin's PoW, the goal is to find a hash that is below a particular target value, often visualized as a hash with a certain number of leading zeros. This target adjusts over time to maintain a consistent block time despite changes in computational power.
f. Mechanism: Bitcoin miners compete to find a hash of the block header that meets the required difficulty level (i.e., has a sufficient number of leading zeros). The difficulty of this task adjusts dynamically with the network's collective hashing power to ensure that the average time to find a block remains consistent.’
It is clear from these references that Dr Wright thought that the proof of work implemented in the Bitcoin system operated on the basis of finding a hash with a sufficient number of leading zeros.
Counsel for Dr Wright put to Dr Back that the Bitcoin code had retained the approach of simply checking leading zeros as described in the Bitcoin White Paper. Presumably this was done on instructions and/or the basis of what Dr Wright said in Wright11. Dr Back explained that although the Bitcoin White Paper refers to leading zeros, no released version of the Bitcoin code utilises that. As he explained,
48:20 the specification is not a number of leading zeros in
21 Bitcoin, the specification is a difficulty which is the
22 floating point number….”
“50: 5 while the Bitcoin paper is expressed in that way, if you
6 actually look into the details and the code and how it
7 works, the difficulty is a floating point number, so
8 it's a little more nuanced than leading zeros…”
In re-examination, Dr Back confirmed that in the Bitcoin code there is no check for leading zeros:
“77: 20 Q. Okay. Does it deal with leading zeros, or ...?
21 A. No.
22 Q. Right.
23 A. So, I mean, I believe this end bit is a, sort of,
24 compact representation of -- it involves a compact
25 representation of the difficulty which, then, in turn,
78: 1 creates a target, and so it's checking if the hash is
2 as -- represented as a very large integer, is less than
3 the target, which is -- which is what I said. So that,
4 you know, superficially, if you look at the zeros, there
5 is a certain number of zeros, but, you know, even if you
6 look at it in binary, there are some more bits after it
7 where, you know, the next bit could be a zero or a one
8 and it could still be an invalid proof-of-work, because
9 it's really a floating point number, or a fraction or
10 something.”
Although in Written Closing, Counsel for Dr Wright spent many paragraphs seeking to persuade me that Wright1 [94] was a fair and accurate description of a technically complex issue, I am not so persuaded. In fact, as I have mentioned, I find [94] (and the surrounding paragraphs) to be fabrication by Dr Wright.
It is unnecessary to get into the rather fine distinctions which were explored in cross-examination of Dr Back when comparing the methodologies of Aura et al, Hashcash and Bitcoin. Dr Back answered all the points put to him fairly and carefully. It may be true that when one conducts a detailed comparison of these three methodologies, the proof-of-work system described in the Bitcoin White Paper ‘aligns more closely with the methodology described in Aura’s paper than with Dr Back’s original proposal’. But that is an exercise using 20:20 hindsight. What Satoshi actually did appears to be much more straightforward. He referred to Adam Back’s Hashcash paper because he was aware of it and, as he stated in the Bitcoin White Paper, his proposed proof-of-work system was similar to it. Either Satoshi was unaware of the proposal by Aura et al, or he considered it different, possibly for the reason given by Dr Back.
Dr Wright’s explanation in [94] does not make sense. If Satoshi had based his proof-of-work algorithm on Aura et al, he would have cited that paper. The fact that Aura had supposedly not responded (per Dr Wright) would not have been a reason not to cite the paper.
In fact, there is a ready explanation as to why Dr Wright got all this wrong. It has become apparent to me that his modus operandi when pursuing his claim to be Satoshi is to do whatever he can to read and research all available materials so he is in a position to speak with authority on what happened/he did as Satoshi. This strategy is not foolproof. It comes unstuck if what Dr Wright thinks happened conflicts with (a) testimony from those who were actually involved at the time or (b) previously unpublished materials. This is yet another instance where Dr Wright has come unstuck. Furthermore, it appears he did not apply this strategy to the Bitcoin Source Code. Consistent with (a) the relatively few forgeries relating to the code and (b) the points he got wrong as regards the code, it would appear he had not analysed or familiarised himself with the code.
There is, of course, an additional problem with Wright1 [94], Wright11 [387] and [601]. In those paragraphs, Dr Wright got wrong the proof-of-work system which Satoshi actually implemented in the Bitcoin Source Code, as Dr Back explained. Satoshi would not have got this point wrong.
Overall, there are a number of independent pieces of evidence which combine to present, in my judgment, an overwhelming case that Dr Wright did not write the Bitcoin Source Code, either by himself or with others. Once again, his evidence that he did is fantasy.
Launch of Bitcoin
‘8. In relation to the launch of the Bitcoin system, Dr Wright has explained his purchase of the bitcoin.org domain; his involvement in the mining of early Bitcoin blocks, which is corroborated by contemporaneous documents and a number of third party witnesses; and his position in relation to the early Bitcoin transfers carried out by Satoshi (and other relevant interactions).’
By way of background, I refer to the following sections in the Appendix which contain my findings that the following documents, relevant to these matters, were forged by Dr Wright:
Section 27: False NAB Account Records, screenshots purporting to show the purchase of a vistomail address in 2008.
I also refer to Section 1 in the Appendix which sets out how Dr Wright’s claims to have acquired the bitcoin.org domain were founded on those forged documents but then foundered or were abandoned.