Len Sassaman — Satoshi Nakamoto Evidence — Byzantine Generals Problem

This article is an addition to the theory posted here, that gives a very compelling series of evidence that Len Sassaman was the true identify of Satoshi Nakamoto. If you haven’t spent the time to do so I would recommend reading it throughly. Regardless if Len was or was not Satoshi he was a great man that tragically took his life due to suffering with depression amongst other health issues. All theories outlined in this article or the previous one are just that, theories. No one will likely ever be able to prove with 100% certainty. Here is a brief, incomplete, list of the evidence laid out in the linked article.

• Len passed away a few months after Satoshi stopped contributing and posting on Bitcoin.
• Len worked directly under David Chaum and with Hal Finney on various projects. Both pioneers in electronic cash systems.
• Len used British English terms and spelling that Satoshi also used on forums.
• Len was online and posting messages at a similar times as Satoshi, pointing to them being in similar timezones.
• Len worked on distributed messaging systems that have many similarities to the Bitcoin protocol design. Most notably he was the maintainer of Mixmaster (a remailer that allowed you to send emails with more anonymity).
• Len was very keen on solving the Byzantine Generals Problem, which would allow synchronization and consensus for distributed system (such as his Mixmaster remailer).

The last two points are the ones that will be of focus here. It is argued one of Bitcoin’s greatest feats and what makes the protocol possible is its ability to reach consensus on a distributed ledger or database without a third party. Effectively Satoshi expanded on Adam Back’s Hashcash system to create a chain of proof-of-work verified blocks to make this possible. Here you can read Satoshi describe how he solved it using proof-of-work in an email chain before the Bitcoin client was released.

If you look at the years 2005–2008 you will see Len has multiple academic papers researching possible solutions to the Byzantine Generals problem and its importance to mix-nets, like his own Mixmaster. The last paper on the subject titled The Byzantine Postman Problem was published in 2008, one year before Satoshi released the alpha version of the Bitcoin client in 2009. In this paper Len describes a way to solve the Byzantine Generals problem though a combination of hashing message blocks and verifying hash trees.

If Satoshi effectively proposed one solution to this problem in distributed systems it would make sense Len would be interested in such a solution and maybe even apply something similar to his own Mixmaster remailer. This can be checked as the Mixmaster repo is still up on source forge.

The first interesting piece, Len’s last release and contribution to Mixmaster was in early 2008. It would make sense if Len was Satoshi he would have moved to working on Bitcoin in his free time as it was released one year later in Jan. 2009.

Similarities between remailers like Mixmaster and Bitcoin have previously been pointed out as even Adam Back suggested “Satoshi might have been a remailer developer.” In some ways Bitcoin is a combination of a remailer and Adam Back’s Hashcash to verify and bring consensus to the ledger as well as to issue new coins.

Remailers represent the “ground floor” of this house of ideas — the ability to exchange messages privately, without revealing our true identities. In this way we can engage in transactions, show credentials, and make deals, without government or corporate databases tracking our every move.

One Cypherpunk vision includes the ability to engage in transactions anonymously, using “digital cash”. … this is another area where anonymous mail is important.

-Hal Finney

Why did Len stop working on Mixmaster? He had plans to keep working on version 3.1, and further into the future as seen in Mixmaster’s “todo” file. A plausible theory is he found a way to solve the Byzantine Generals problem. A problem he has been pondering for years. A problem that was solved using a Hashcash proof-of-work system.

And in Len’s last release ever of Mixmaster in 2008 he has an item under todo that was not seen in previous releases.

Whether this is a complete coincidence could be argued. Hashcash could be implemented to combat spam in a remailer and not to solve the Byzantine General problem or issue an e-cash currency. Or one could argue, in Len’s brilliant mind, while pondering how to implement Hashcash into his remailer he came up with a novel solution to the Byzantine General problem. We at least know Len was aware of Hashcash in late 2007/early 2008 and was planning on implementing it on his Mixmaster remailer system.

One final coincidence found in the Mixmaster code base is there seems to be a remailer node operator using a Japanese alias and the only one with a GMX domain email address ;)

This brings us to the last bit of evidence and the most telling. What was Len working on after March 2008 until his death? One could argue he was strictly working on his Phd. But I find it hard to imagine he would stop working on his Mixmaster remailer, a project he has been contributing to for over 6 years, out of the blue. He never got around to adding Hashcash. It seems he stopped obsessing over a solution to the Byzantine Generals problem nor ever care to comment on how Bitcoin solved it in a novel way using ideas similar to those in his own academic papers. Which doesn’t add up if you look at how excited Len was on a blog post when a single person from Stanford wrote a paper related to the Byzantine Generals problem in June of 2008, 7 months before the release of Bitcoin.

But what is written later in the blog post I believe is the best evidence in favor of a single person being Satoshi.

In June 2008, Len was actively working on a protocol to solve the Byzantine Generals problem and hoped to have one done “soon”. It could be he never completed it, never published any code on it, never wrote another paper about it.

I believe Len may have poked enough sticks at it to get it right.

Side note — Notice Len uses both “we” and “I” when discussing the protocol he is working on. “We” is used in the context of a group of individuals researching how to solve the Byzantine Problem. “I” is used when the discussing the development and implementation of such protocol. Suggesting multiple people involved in the research behind the solution, while he seems to be the one keen on implementing it in the real world. This similar pattern is seen in the Bitcoin Whitepaper as plural pronouns are used regarding the research. ex. “We propose a solution to the double-spending problem…”. After the paper Satoshi almost exclusively uses “I”. It would make sense to assume the “we” are the few initial researchers, along with Satoshi, theorizing about a possible solution. While the I is Satoshi/Len, the author of the software and the main/sole individual behind the Satoshi pseudonym.