Len Sassaman and Satoshi: a Cypherpunk History

Evan Hatch
19 min readFeb 22, 2021


We’ve lost too many hackers to suicide. What if Satoshi was one of them?

Embedded on every single node of the Bitcoin network is an obituary. Hacked into the transaction data, it’s a memorial to Len Sassaman, a man essentially immortalized in the blockchain itself. A fitting tribute in more ways than one.

Block 138725

Len was a true Cypherpunk— equal parts brilliant, irreverent, and idealistic. He devoted his life to defending personal freedoms through cryptography, working as a developer on PGP encryption and open-source privacy technology, as well as an academic cryptographer researching P2P networks under blockchain inventor David Chaum.

He was also a pillar of the hacker community: a friend and influence to so many of the important figures in the history of infosec and cryptocurrency.

Losing Satoshi

By all accounts, Len was on track to be one of the most important cryptographers of his time. But on July 3rd, 2011, he tragically took his own life at 31, following a long battle with depression and functional neurological disorders.

His death coincided with the disappearance of the world’s most famous cypherpunk: Satoshi Nakamoto. Only 2 months before Len died, Satoshi sent their final communication:

I’ve moved on to other things and probably won’t be around in the future.

After 169 code commits and 539 posts in the span of a year, Satoshi disappeared without explanation. They left behind a slew of uncompleted features, raging debates about their vision for Bitcoin, and a still-untouched fortune of $64B in BTC.

We’ve lost too many hackers to suicide. Aaron Swartz. Gene Kan. Ilya Zhitomirskiy. James Dolan. All of them victims of stigma and an epidemic that has exacted a price on technological progress itself. Imagine if the creator of Bitcoin died well before they could see it through. And if that were true, what would they have given the world had they been treated with the concern and dignity they deserved?

I hesitate to speculate about Satoshi’s identity, given that the discourse has generally ranged from misguided to downright idiotic and unethical. But with Craig Wright fraudulently claiming credit for the creation of Bitcoin, it’s important we revisit the topic and recenter the discussion around the Cypherpunks who actually built Bitcoin.

Whoever Satoshi was, they were very much ‘standing on the shoulders of giants’ — Bitcoin was the culmination of decades of accumulated research and discourse within the Cypherpunk community. In this sense, Len was unequivocally an indirect contributor. Yet one has to wonder who actually wrote the code, ran the first node, and posted using the Satoshi pseudonym.

To synthesize and implement the myriad ideas Bitcoin was based on, that person or group of people would have required a unique combination of expertise spanning public key infrastructure, academic cryptography, P2P network design, practical security architecture, and privacy technology. They would likely have been deeply engrained in the Cypherpunk community and adjacent to the figures who proved to be major influences on cryptocurrency. Finally, they would have needed the ideological conviction and hacker ethos to ‘roll up their sleeves’ and anonymously build a real-world version of ideas that had previously been relegated to the realm of theory.

When I consider Len’s life, I see many of these same traits and I think there is a real possibility that Len was a direct contributor to Bitcoin.

In light of the unprecedented attention that cryptocurrency is receiving, I’m hopeful I can bring attention to one of the ‘unsung heroes’ to whom we owe credit. I also hope that we can reflect on the immense importance of addressing mental illness and especially functional neurological disorders that deserve far more attention.


Even in his youth, Len was a self-taught technologist who gravitated towards cryptography and protocol development. Despite living in small-town Pennsylvania, by 18 Len was on the Internet Engineering Task Force responsible for the TCP/IP protocol underlying the internet and later the Bitcoin network.

“Always kind of the odd kid because he was smart”, Len was diagnosed with depression as a teenager. Unfortunately, he suffered traumatic experiences at the hands of “borderline sadistic” psychiatric practitioners, experiences which would presumably leave one distrustful of purported authority figures.

In 1999, Len moved to the Bay Area and quickly became a regular in the Cypherpunk community. He moved in with Bram Cohen, creator of Mojo and Bittorrent, and was a contributor to the legendary Cypherpunk mailing list where Satoshi first announced Bitcoin. Other hackers remember him as intelligent and lighthearted, chasing down a squirrel at a Cypherpunk meeting and speeding around in a sports car with a ‘Get Out of Jail Free’ card in case he was pulled over.

In SF, Len devoted himself to defending personal liberties and privacy through both technological and political direct action. At 21, he made headlines for organizing protests against government surveillance, as well as the imprisonment of hacker Dmitri Skylarov.


Early in his career, Len distinguished himself as an authority in public-key cryptography — the foundation of Bitcoin. By 22, he was presenting at conferences and had founded a public key crypto startup with famous open-source activist Bruce Perens.

After the startup collapsed in the wake of the Dot-com Bubble, Len joined Network Associates to help develop PGP encryption central to Bitcoin. Working on the release of PGP7 in 2001, Len set up interop testing for OpenPGP implementations, putting him in touch with many important crypto pioneers. Len also contributed to the GNU Privacy Guard implementation of OpenPGP and worked with PGP inventor Phil Zimmerman to invent a new cryptographic protocol.

When introducing Bitcoin, Satoshi said he hoped Bitcoin could be “the same thing for money” that strong cryptography (i.e. PGP) was for securing files.

A generation ago, multi-user time-sharing computer systems had a similar problem. Before strong encryption, users had to rely on password protection…

Then strong encryption became available to the masses, and trust was no longer required. … It’s time we had the same thing for money.

Hal Finney

At Network Associates, Len worked on PGP alongside Hal Finney. Finney was the second PGP developer and helped create the RFC 4880 standard for OpenPGP interoperability. He was also the earliest and most important contributor to Bitcoin after Satoshi:

Unsurprisingly, Finney is one of the most popular candidates for Satoshi, though this implies that Finney faked his extensive email interactions with Satoshi and simultaneously contributed to Bitcoin under both his real name and a separate fake identity. Finney would also continue to work on Bitcoin well after Satoshi had “moved on” in 2011.


Len and Finney shared one very rare and relevant skillset: they both were developers of the remailer technology that was a precursor to Bitcoin.

Proposed by David Chaum alongside cryptocurrency, remailers are specialized servers for sending information anonymously or pseudonymously. It was very common to use them when contributing to the Cypherpunk Mailing list, which itself was built on distributed remailers.

Diagram of a Type II Remailer

While early remailers simply forwarded info while obsfucating a sender’s identity, later protocols like Mixmaster (the most popular remailer) relied on decentralized nodes to distribute fixed-sized blocks of encrypted info across a P2P network. Bitcoin’s architecture is very similar to that of remailers, although its nodes transmit transaction data in place of messages. In 1997, Crypto-anarchist founder Tim May even proposed a digital currency built on remailers.

As a primary developer, node operator, and principal maintainer for Mixmaster, Len was an eminent expert in remailer technology. He also implemented similar technology as a systems engineer and security architect for the Anonymizer privacy guard.

Not only were remailers a direct technological progenitor of Bitcoin, they were fundamental to its intellectual history. In the essay Why Remailers, Finney argued that remailers were the foundation of an anonymous digital economy.

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.

Remailer operators were some of the first to recognize the need for cryptocurrency: without a means for anonymous payments, remailers had to be run altruistically at their operator’s expense. This introduced scalability issues and meant that spam and abuse were a constant problem. Because of this, many concepts fundamental to cryptocurrency emerged from the need for an abuse-resistant, for-profit remailer:

  • In 1994, Finney proposed that remailers could be monetized via anonymous “coinsand “cash tokens”.
  • Smart contracts were first discussed in the context of preventing remailer abuse. Nick Szabo’s prescient 1997 paper on smart contracts specifically references Mixmaster.
  • Ian Goldberg and Ryan Lackey (both of whom Len knew) were major figures in the remailer community who worked on an unfinished cryptocurrency called HINDE in 1998. Ian later created several early ecash clients and Ryan went on to become CSO of Tezos.

Accordingly, Satoshi’s second post about Bitcoin stated that pay-to-send email was Bitcoin’s first working use case.

Initially it can be used in proof-of-work applications for services that could almost be free but not quite.

It can already be used for pay-to-send e-mail. The send dialog is resizeable and you can enter as long of a message as you like.

Adam Back

Crossing paths with Len in the small remailer community was Blockstream CEO Adam Back — the first person to communicate with Satoshi.

Back’s own interest in cryptocurrency started from running a remailer, and he created the HashCash proof of work system for remailer operators to combat spam and DDOS attacks. Satoshi would later use HashCash as the basis of Bitcoin’s mining.

We know that Len directly collaborated with Back, listing him as a contributor to a research paper as well as a Mixmaster memo. Both worked on numerous OpenPGP implementations and were connected in each other’s PGP web of trust.

Interestingly, Back himself has suggested that Satoshi might have been a remailer developer, noting that the devs would “[practice] their own technology” to pseudonymously contribute to cryptographic protocol discussions. Unlike many Cypherpunks discussed, we know that Len made extensive pseudonymous contributions to the Cypherpunk mailing list via remailers.

Bram Cohen’s response to this article, suggesting he and Hal Finney could have pseudonymously collaborated

Chaum & COSIC

After high school, Len worked to support his family and never had the chance to attend college. In spite of this, in 2004 he secured his “dream job” as a researcher and Ph.D. candidate at COSIC, the Computer Security and Industrial Cryptography Research Group of K.U. Leuven in Belgium.

Len’s Ph.D. advisor at COSIC was none other than “father of digital currency” David Chaum. While Chaum laid the groundwork for the entire Cypherpunk movement and all cryptocurrencies, few could claim to have worked with him directly.

A few of Chaum’s relevant accomplishments:

  • The invention of cryptocurrency in his 1983 paper Blind Signatures for Untraceable Payments.
  • The invention of the blockchain, with his 1982 dissertation including code for all but one element of the blockchain detailed in the Bitcoin whitepaper.
  • The creation of the first electronic cash system with his company Digicash. Anonymous payment between digital pseudonyms was central to this vision.

“[Chaum] stands in the thick of a movement that seems unstoppable — the digitization of money … the wild card in the era of digital money is anonymity, and David Chaum thinks we’re in trouble without it”

While Digicash failed (partially due to a reliance on centralized systems), Chaum wanted to create a second digital currency that would offer a combination of anonymity and practicality.

While many saw its failure as proof that digital cash was infeasible, Satoshi defended the “old Chaumian currencies” while acknowledging the issues caused by centralization.

A lot of people automatically dismiss e-currency as a lost cause because of all the companies that failed since the 1990’s. I hope it’s obvious it was only the centrally controlled nature of those systems that doomed them.

Len’s Research

Len worked at COSIC in Belgium until his death in 2011. In that time, he accumulated an impressive 45 publications and 20 conference committee positions.

Len’s research was focused on developing privacy-enhancing protocols with “real-world applicability” and working code. His main project (aided by Bram Cohen) was the Pynchon Gate, an evolution of remailer technology that allowed for pseudonymous information retrieval via a network of distributed nodes without a trusted 3rd party.

Pynchon Gate and meta-index + bucket pool architecture

This work was very pertinent to Bitcoin — as work on the Pynchon Gate progressed, Len became increasingly focused on finding solutions for the Byzantine Fault (aka Byzantine Generals Problem) that had been a major obstacle for earlier P2P networks.

Diagram of the Byzantine Fault

In the context of distributed computing, Byzantine fault tolerance refers to the ability of a network to remain functional even when nodes are compromised or unreliable. The Byzantine Fault was one of the biggest problems that needed to be solved for a secure, decentralized cryptocurrency without double-spending or the need for trusted 3rd parties. Satoshi’s most important innovation was a ‘triple-entry’ accounting system that solved this using the blockchain introduced by Chaum.

During Bitcoin’s development in 2008–2010, Len was increasingly active in financial cryptography. He joined The International Financial Cryptography Association and presented at the Financial Cryptography and Data conferences, where he also held a committee seat. The latter was founded by Robert Hettinga, an early and prominent advocate for digital cash, which was a major topic at the conferences.

Satoshi as Academic

Numerous clues suggest that Satoshi was working in academia during Bitcoin’s development, an idea embraced by Bitcoin Foundation founder Gavin Andersen.

“I think he’s an academic, maybe a post-doc, maybe a professor who just doesn’t want the attention”.

Satoshi’s code contributions and comments ramped up heavily during summer and winter break, but tapered off in late spring and the end of year, when an academic would have been taking and/or grading finals.

The idiosyncratic construction of Bitcoin’s code also suggests that Satoshi had an academic background. It has been described as “brilliant but sloppy”, eschewing conventional software development practices like unit testing but exhibiting cutting-edge security architecture and an expert understanding of academic cryptography and economics.

Whoever did this had a deep understanding of cryptographyThey’ve read the academic papers, they have a keen intelligence, and they’re combining the concepts in a genuinely new way.

When prominent security researcher Dan Kaminsky first reviewed Satoshi’s code he tried to pentest it with 9 different exploits, but was amazed to find that Satoshi had already anticipated and patched out all of them.

“I came up with beautiful bugs, but every time I went after the code there was a line that addressed the problem. … I’ve never seen anything like it.”

This might suggest that Satoshi and Kaminsky had a shared set of infosec experiences and expertise. Coincidentally, Len and Kaminsky co-authored and presented a paper demonstrating methods for attacking public key infrastructure.

Additionally, the Bitcoin whitepaper was released in a medium rarely seen on the Cypherpunk mailing list — a LaTeX formatted research paper with academic trappings such as an Abstract, Conclusion, and MLA citation. Compare this to other proposals like Bitgold and b-money which were unstructured blog posts.

Satoshi in Europe

Since COSIC was based in Leuven, Len was living in Belgium during Bitcoin’s development. This is salient given that a number of facts suggest that Satoshi was based in Europe — the primary focus of an early inquiry by The New Yorker.

Satoshi’s writing exhibits spelling and word choices idiosyncratic of British English such as bloody difficult”, “flat”, “maths”, grey”, as well as the dd/mm/yyyy date format. However, Satoshi also refers to Euros rather than pounds.

Bitcoin’s Genesis Block also included a headline from that day’s copy of The Times newspaper (“The Times 03/Jan/2009 Chancellor on brink of second bailout for banks”). This headline was specific to the print version, which was only circulated in the UK and Europe. In 2009, The Times was a Top 10 newspaper in Belgium and “heavily used by scholars and researchers because of its widespread availability in libraries and its detailed index”.

These clues leave us with a paradox: they suggest Satoshi was European, yet someone with the requisite skillset and exposure to Bitcoin’s primary influences would likely have been American. Much of the Cypherpunk community coalesced conferences and meetups, part of why a disproportionate number hailed from America and especially SF. The jobs where one could have gained cutting-edge professional infosec and crypto experience were similarly concentrated in the US.

Strangely enough, Len used the very same British English as Satoshi even though he was American.

Analysis of Satoshi’s posting history suggests they were a European ‘night owl’ who worked on Bitcoin after returning from a job or school during the day. At one point, Satoshi also stated that an increase in mining difficulty happened “yesterday”, which would not have been true if they lived in the US.

Assuming Satoshi lived a life outside Bitcoin, he did so during the working/academic day when he was largely away from his computer at home … if Satoshi lived in a BST timezone he worked mostly at night, often into the small hours

And when we examine Len’s tweet history, we see that timestamps of Satoshi’s posts and code commits correspond closely to Len’s own hours of late-night activity.

P2P Networking

While not the first cryptocurrency, Bitcoin was the first to be based on a fully P2P, distributed network. The importance of this is emphasized in Satoshi’s very first reference to Bitcoin:

I’ve been working on a new electronic cash system that’s fully peer-to-peer, with no trusted third party

In order to build Bitcoin, Dan Kaminsky stated that Satoshi would have needed to “understand economics, cryptography, and P2P networking”, and Len had an unusually early and intimate exposure to all 3, along with their application to digital currency.

Bram and Len in an interview about CodeCon

While in SF, Len lived and collaborated with Bram Cohen, creator of most widely used P2P protocol: BitTorrent. During this period (2000–2002), Bram developed a revolutionary P2P network called MojoNation which used a digital currency of “Mojo tokens”, making it one of the first digital currencies to see a working public release.

In MojoNation’s P2P economy, “tokens” could be exchanged for the storage of files, which would be encrypted and encoded into “blocks” uploaded to a distributed network of nodes hosting a public ledger, recalling Bitcoin’s own system of distributed bilateral accounting. Mojo was not merely an internal accounting token but a full currency — it could be exchanged for dollars and visa versa. Some of the first discussions of tokenomics concern the mechanics of Mojo tokens.

A unit of Mojo represents a slice of the current capabilities of the system as a whole. If you perform work for me now I give you credits, in the future when the network is larger those credits will represent a slice of a much larger pie and so have increased in value when you spend them.

Satoshi discusses tokenomics in a very similar way:

It has the potential for a positive feedback loop; as users increase, the value goes up, which could attract more users to take advantage of the increasing value.

While visionary, MojoNation’s economy quickly collapsed due to hyperinflation. Satoshi consciously designed Bitcoin to avoid this fate via built-in deflation and non-reliance on a central “mint” server.

In 2001, Bram launched BitTorrent. As a P2P alternative to the centralized Napster, BitTorrent foreshadowed Bitcoin’s own distributed node-based topology and system of consensus, as well as its protocol-level incentive system. BitTorrent innovated on networks like Gnutella not only at a technical level but also by using economic incentives and game theory.

Bittorent’s design compared to Napster

Presciently, Len told Bram that “BitTorrent would make him bigger than [Napster founder] Sean Fanning”. Satoshi would later reference Napster when explaining the need for a fully decentralized network.

Governments are good at cutting off the heads of a centrally controlled networks like Napster, but pure P2P networks like Gnutella and Tor seem to be holding their own.

Coincidentally, Len and Tor founder Roger Dingledine both worked on the Mixminion remailer protocol, co-presented at Black Hat, and founded the HotPETS conference together.

In 2002, Len and Bram co-founded a conference called CodeCon, which was focused on “highly practical projects with working code”. At CodeCon 2005, Finney introduced Reusable Proofs of Work via a modified BitTorrent client that sent P2P digital currency. One commentator described this as:

…the world’s first transparent server, which could facilitate a world of distributed, cooperating RPOW servers.

Digital currency was a prominent subject at the first CodeCon, which included a demonstration involving Adam Back’s HashCash as well as Zooko presenting Mnet, a fully open-source and decentralized successor to MojoNation. Mojo wasn’t tied to a single company and could be independently audited, both of which Satoshi considered crucial.

Screenshot of the Mnet client

MojoNation co-founders Zooko Wilcox and Jim McCoy also proved to be inspirations for Bitcoin and cryptocurrency pioneers in their own right. Zooko was one of Satoshi’s first collaborators as well as an employee of David Chaum at Digicash and when releasing Bitcoin v0.1 on Bitcoin.org, Satoshi included a link to Zooko’s blog. Zooko would later go on to found major privacy-focused cryptocurrency Zcash. he created the oft-discussed “Zooko’s triangle” framework.

“Zooko’s triangle is a trilemma of three properties that are generally considered desirable for names of participants in a network protocol”

McCoy also is a major influence within cryptocurrency, and Ryan Selkis of Digital Currency Group has stated his belief that McCoy could be Satoshi.


Even by the standards of the Cypherpunk community, both Len and Satoshi had especially strong ideological convictions and commitments to open knowledge.

I wish you wouldn’t keep talking about me … maybe instead make it about the open-source project and give more credit to your dev contributors

Satoshi’s ‘hacktivist’ approach of distributing Bitcoin via a free, open-source grassroots project contrasts starkly with their predecessors. Chaum, Stefan Brand, eCash, and others took a very different approach: filing patents, founding closed source venture-backed companies, and attempting to drive adoption via corporate partnerships.

This paralleled Len’s own extensive contribution to open source projects like PGP, Mixmaster, GNU Privacy Guard, and others, as well as his extensive volunteer experience with groups like Shmoo Group.

In response to this story, Bram stated that Len had a predilection for anonymous releases

Satoshi alluded to their ideological leanings on a few occasions, saying that said Bitcoin was “very attractive to the libertarian viewpoint” and that it could “win a major battle in the arms race and gain a new territory of freedom for several years”.

Len was similarly passionate about the need to defend open knowledge and technological advancement from corporate and governmental interference.

The quest for knowledge is a fundamental part of being human. Any kind of prior restraint against that is in my opinion a violation of our freedom of thought and conscious. So, not only am I hopeful that we can avoid overly restrictive knee-jerk legislation. …. I don’t want to see anyone build a framework that could be misapplied for that purpose.


Just as Satoshi created Bitcoin from behind a pseudonym, Len was in a sense forced to live behind a persona of his own. Following an incident in 2006, Len suffered from increasingly severe non-epileptic seizures and functional neurological problems, which served to exacerbate the depression he had battled since youth.

As a victim of stigma, Len felt like he had to keep up this facade of being the same hyper-competent guyand was “absolutely terrified” that his declining health would bring an end to his work and disappoint the people he cared about.

Despite these challenges, Len continued to work until months before his death, contributing to papers and even presenting at Dartmouth. Sadly, he was successful in concealing the severity of his situation from almost everyone in his life.

There were very very few people who had any idea just how far things had gone … the one refrain I heard over and over was “we never knew, it seemed like he was doing fine”.

Len presenting at Dartmouth shortly before his death

Just as Len built on ideas that came before him, one gets the sense that he was devoted to building things that would outlast him, one reason he was committed to open source and open knowledge.

This is our heritage, this research, these ideas that we have, that is leading to knowledge that no human in history has had the opportunity to have before, this is what we’re going to be handing down to future generations. We need to make sure we are not backed into a corner where we are not able to distribute this research to others, and that this isn’t locked up in IP lawyer vaults.

When Len’s passed away in 2011, it represented a huge loss for the Cypherpunk and the tech community at large, a fact reflected in the huge outpouring of memories and sympathy that followed. One comment in particular still stands out to me: a Hacker News post from “pablos08”.

I became friends with Len and we were coconspirator cypherpunks at a time when that was a wild frontier. We were reimagining our world, riddled with cryptosystems that would mathematically enforce the freedoms that we treasured. Anonymous remailers to preserve speech without fear of retribution; onion routers to ensure nobody could censor the internet; digital cash to enable a radically free economy. We have schemes to decentralize & distribute everything.

We imagine complex and esoteric threats to problems we might someday have — we architect futuristic protocols to insulate against those threats. All this is a highly academic geek utopia exercise. I tend to keep it that way, but Len wanted to get his hands dirty.

Cypherpunks write Code.

Postface: Please respect the privacy and emotional health of Len’s family and friends. Len’s laptop was encrypted and the password is lost. Prying into their personal lives is not only unethical, but futile.

…I loved him and I miss him. It doesn’t mean I know everything there was to know.

He used FileVault. I do not know what his password was. No matter how much you want to know whether he was Satoshi, it is impossible for me to access his laptop or any files on it. That door is closed.