There's a curious thing about Bitcoin that not many people know.

Buried in block 138,725 of the blockchain, among transaction data and code, is an obituary. Someone deliberately placed it there, so that it would be forever etched in every node of the network. So that as long as Bitcoin exists, this tribute will exist too.

It's a tribute to Len Sassaman.

---BEGIN TRIBUTE--- 
#./BitLen           
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=-=-=-=-=-=-=-=-=-= 
LEN "rabbi" SASSAMA 
     1980-2011      
Len was our friend. 
A brilliant mind,   
a kind soul, and    
a devious schemer;  
husband to Meredith 
brother to Calvin,  
son to Jim and      
Dana Hartshorn,     
coauthor and        
cofounder and       
Shmoo and so much   
more.  We dedicate  
this silly hack to  
Len, who would have 
found it absolutely 
hilarious.          
--Dan Kaminsky,     
Travis Goodspeed    
P.S.  My apologies, 
BitCoin people.  He 
also would have     
LOL'd at BitCoin's  
new dependency upon 
   ASCII BERNANKE   
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----END TRIBUTE----

The first time I read that, I paused for a moment. Because it's no small thing. The Bitcoin blockchain is immutable by design: what goes in, doesn't go out. Whoever did that chose the most permanent place in the crypto ecosystem to tell the world that this man mattered.

That's what led me to spend several days investigating who he really was. What I found was a life that can hardly be summarized.

I'm going to try anyway.

Pennsylvania, 1980Pennsylvania, 1980

Leonard Harris Sassaman was born on April 9, 1980, in Pottstown, Pennsylvania. He grew up in a quiet environment, was diagnosed with depression as a teenager, and from a young age developed an obsession with understanding how systems worked: computers, networks, the protocols that make the internet what it is.
He didn't finish a conventional university degree. What he did was something rarer and, I think, more interesting: he went straight into the real work.

At 18, he was already part of the Internet Engineering Task Force, the group responsible for the TCP/IP protocols that are literally the backbone of the internet. Eighteen years old. While most people that age are trying to figure out what to study, Len was already at the tables where decisions were being made about how the global network would work

That says a lot about who he was.

San Francisco and the CypherpunksSan Francisco and the Cypherpunks

In 1999, he moved to the San Francisco Bay Area, where he quickly became a regular member of the cypherpunk community and roommates with Bram Cohen. If that name doesn't ring a bell (as it didn't for me): Bram Cohen is the creator of BitTorrent. Len arrived in San Francisco and ended up living with one of the most influential programmers of his generation.

As such, he began accumulating projects at a speed that is impressive in retrospect.
He worked for Network Associates developing the PGP encryption software, was a member of the Shmoo Group, contributed to the IETF's OpenPGP working group, and to the GNU Privacy Guard project. PGP, for those unfamiliar with it, is the email encryption standard that remains the foundation of secure communication on the internet. Len didn't invent it—that was Phil Zimmermann—but he helped keep it alive and update it when the project went through difficult times.

Together with Zimmermann, he created the Zimmermann-Sassaman Key Signing Protocol, which accelerates the verification of the public key's digital fingerprint. A technical detail that sounds dry but greatly simplified the process of verifying identities in the crypto ecosystem.
He was also, for years, the main maintainer of the Mixmaster code, the most popular anonymous remailer of its time, and personally operated the randseed node.

Here it's worth pausing for a moment to understand what a remailer is, because it's important for understanding the full story.

A remailer is, basically, a server that receives messages and forwards them, eliminating any trace of who originally sent them. Mixmaster was the most sophisticated of all: it operated on a decentralized network of nodes that distributed fixed-size blocks of encrypted information through a P2P network. Does that sound familiar? It should. Bitcoin's architecture is remarkably similar to that of remailers, although instead of messages, it transmits transaction data.

At 21, he organized protests against US government surveillance and the imprisonment of Russian programmer Dmitry Sklyarov, who had been arrested in the United States for giving a presentation on the weaknesses of Adobe's eBook protection system. Apparently, Len wasn't one to stand idly by.

In 2002, along with Bram Cohen, he co-founded CodeCon, a conference focused on software projects with real, working code, no hype or empty presentations. This conference became a key meeting point for the most serious hackers in the ecosystem. It was held annually until 2009.

Belgium and David ChaumBelgium and David Chaum

In 2004, a pivotal event occurred in his career: Sassaman landed what he described as his "dream job"—a PhD position with the COSIC research group at KU Leuven in Belgium. His thesis advisor was David Chaum.
That name is significant. Chaum is the cryptographer who, in the 1980s, theoretically invented the concept of anonymous digital cash and the blind signature protocols that form the theoretical foundation for nearly all subsequent privacy-focused cryptography. In many ways, he is the intellectual grandfather of Bitcoin. Having Chaum as a PhD advisor at that time was akin—in soccer terms—to training directly under the coach who invented the tactical system used by everyone else.

https://len.sassaman.net/

Len’s main project in Belgium, developed alongside Bram Cohen, was Pynchon Gate: an evolution of remailer technology that allowed for the pseudonymous retrieval of information via a network of distributed nodes, without the need for a trusted third party. While working on this project, Len became increasingly focused on solving the Byzantine Generals Problem—the major obstacle to building a truly decentralized P2P network without a single point of failure. This is precisely the problem Satoshi Nakamoto solved with the blockchain.

So far, this is the story of a brilliant cryptographer in the right place, at the right time, asking the right questions.

July 3, 2011July 3, 2011

On July 3, 2011, Len Sassaman passed away at the age of 31 following a long battle with depression and functional neurological disorders. His wife, computer scientist Meredith Patterson, shared the news with the cypherpunk community that same day. Shortly thereafter, his friend Dan Kaminsky—one of the industry's best-known security researchers—encoded a tribute to Len into block 138,725 of the Bitcoin blockchain, describing him as "a friend, a kind soul, and a cunning prankster."

Since then, every Bitcoin node in the world has carried that inscription on its hard drive.

The theory. Saved for last—and addressed honestly.The theory. Saved for last—and addressed honestly.

I’m leaving this for last because I believe it’s the right thing to do. Len Sassaman’s story doesn’t need speculation about Satoshi to be significant; his work holds value in its own right, independent of the mystery surrounding it.

That said, the theory exists, carries some intellectual weight, and it would be dishonest to ignore it.
Evan Hatch’s 2021 essay was the first to systematically document the coincidences: the exact technical profile; the direct connections to Hal Finney and Adam Back; the work addressing the very problems Bitcoin solved; and the mastery of the remailers Satoshi likely used to maintain anonymity. Len’s death in July 2011 occurred just two months after Satoshi Nakamoto’s last known public message.

Adam Back himself has suggested that Satoshi might have been a remailer developer, noting that such developers "practiced what they preached" by using their own technology to contribute pseudonymously to cryptographic discussions. Len was exactly that kind of developer.
However, to be honest: there is no direct proof. His wife, Meredith Patterson, has publicly stated that Len was not Satoshi Nakamoto.

There is also a recent Medium essay by Peter Miller titled "Len Sassaman was not Satoshi Nakamoto," which examines these coincidences with equal rigor but reaches the opposite conclusion.

I don’t know. No one knows for sure.

What I do know is that a 31-year-old man—who built some of his generation’s most important privacy tools, studied under the theoretical inventor of digital cash, and spent years working on the very problems Bitcoin solved—is forever etched into the blockchain of that same network. Someone deemed that the right place for his memory.

It might have been just a friend making a beautiful gesture.

Or it might have been something more.

Other linksOther links

1. English Wikipedia — Len Sassaman
2. Lifeboat Foundation — Len Sassaman Bio
3. CriptoNoticias — Who was Len Sassaman?
4. Bit2Me Academy — Who is Len Sassaman?
5. BitcoinWiki — Len Sassaman
6. Nakamoto Research — Len Sassaman