Ecash Community Builds Multiple Implementations to Bolster Decentralized Custody

BTC++, Berlin, and breakthroughs in advancing Bitcoin custody

Several weeks back, I made the case that the Bitcoin ecosystem was posing the wrong question, habitually framing everything as “trusted” versus “trustless.” Instead, I recommended that people ask “How many independent things have to go wrong before you lose your money?”

This is a guest post by Obi Nwosu, Co-Founder of Fedi and Fedimint. The views expressed are his own and do not necessarily reflect those of BTC Inc. or Bitcoin Magazine.

Consider Liquid, or Coldcard a few weeks earlier. In the most succinct terms, Matt Corallo put the problem: running identical software means encountering identical bugs.

Fedimint was equally subject to that criticism, and I readily admit it. Our design aimed to eliminate individual people and institutions as single points of failure. However, at that time only one implementation of the protocol existed — a software monoculture underneath human federations. That was not sufficiently secure.

I am pleased to report that Fedimint developers have already taken action.

During the Ecash Hackday in Berlin, the Fedimint team succeeded in operating a single federation using three distinct implementations, with one built by thesimplekid from Cashu.

Had a great time at Ecash Hackday in Berlin, got a Fedimint running with 3 different implementations by @thesimplekid, me and the Fedimint team!

Already got 3 Fedimint implementations now, who will build the 4th one? https://t.co/TnttZYOBKR pic.twitter.com/2MPdtlaJqt

— elsirion (@EricSirion) September 30, 2026

Three separate codebases, a single federation, jointly safeguarding funds. Developers have started to address the monoculture I highlighted several weeks prior. The team's reaction was to pose the question of who will construct the fourth implementation, precisely the mindset I had hoped for.

Calle applied the same concept in his own distinct manner. At bitcoin++ he introduced Federated Cashu, built so that no single operator is solely responsible for a user's funds. Any group of four or five can keep the federation running, based on a novel blind signature scheme.

. @callebtc unveils “Federated Cashu” at @btcplusplus

“You don’t need to trust the operator with your privacy, but you do need to trust the operator with your security”

“Any combination of 4/5 continues the federation”

A new Blind BLS signature scheme is involved. pic.twitter.com/S8iL9Qaa9u

— Matthew Vuk (@matthewvuk2) October 1, 2026

Two teams, two methods, but a common objective: ecosystem resilience, achieved within a matter of weeks.

Fault tolerance is not derived solely from trustworthiness, regardless of the quality of audits, formal verifications, and security culture. It stems from independent failure domains. No single bug, vendor, or jurisdiction can bring down everything at once.

Let me clarify the layers, as the distinction is important. Fedimint is the open-source protocol; Fedi is the application we build on top of it. As the protocol gains a second and third implementation, every federation becomes more resilient, and no member needs to alter their wallet usage. Guardians can operate disparate software while still serving the same users.

I outlined five layers where independence must be maintained, and I will abide by them myself:

• Every protocol that holds funds should have multiple implementations.
• There should be multiple wallet implementations.
• Keys should be generated on hardware sourced from different vendors.
• Behind every system that holds money, there should be multiple independent, trustworthy individuals whose privacy is safeguarded.
• Distribution across different geographies and jurisdictions, since a jurisdiction's regulations can shift overnight.

The developers who participated in Berlin brought those five layers nearer to fruition.

My gratitude goes to all who persevere in building and openly sharing their proof-of-work. As for the rest of us, including myself: we have not finished. Our ecosystem must begin to require independence at every layer — software, hardware, humans, jurisdictions, all the way down.

That is the means by which we preserve users' trust in Bitcoin as we move into an era of AI-aided threats to the ecosystem.