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bitcoin++ Berlin, payments edition
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federating ecash
- Time
- Thu, Oct 1 · 12:15 PM – 12:45 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
tbd
Building a Bitcoin POS With Merchants, Not For Them
- Time
- Thu, Oct 1 · 12:45 PM – 1:15 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
A field report from building Numo, an open-source Bitcoin tap to pay POS. This talk walks through the feedback loop: how testimonials, feedback, feature requests drove priority, how we approached user testing, where merchant needs diverged from developer assumptions, and what a merchant first UX actually demands.
Bark: Self-custodial bitcoin payments without head-aches
- Time
- Thu, Oct 1 · 1:15 PM – 1:45 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
Steven Roose, CEO of Second and the earliest engineer to work on the Ark protocol, joins us to talk about Bark and how it's revolutionizing payments on Bitcoin.
The Fiat Payment Stack Returns (Part 2), The Sequel
- Time
- Thu, Oct 1 · 1:45 PM – 2:30 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 45m
further thoughts on how fiat payments suck and how various bitcoin tech (not just lightning!) improves on it.
Bitcoin Payments in the Real World - Lessons from Africa
- Time
- Thu, Oct 1 · 3:30 PM – 4:00 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
Bitcoin payments are moving from experiments into real-world use, especially in markets where people already rely heavily on mobile money. This talk explores what happens when Bitcoin and Lightning meet existing financial rails, drawing from our experience building payment solutions for everyday users across Africa. I’ll share the lessons, opportunities, and challenges we’ve encountered while making Bitcoin easier to use for everyday payments, and what this could mean for the next wave of Bitcoin adoption globally.
Atomic Swaps Across Bitcoin L2s
- Time
- Thu, Oct 1 · 12:15 PM – 12:45 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 30m
Each Bitcoin Layer 2 protocol solves a different problem, each holds liquidity in isolation. The result is a fragmented ecosystem where value cannot flow freely between layers and building payment or swap functionality means integrating each protocol separately. This talk covers how KaleidoSwap approaches cross-layer atomic settlement on Lightning: the protocol design behind trustless swaps across heterogeneous environments, the technical challenges of building an RFQ engine on RGB Lightning, and what it took to ship the first RGB asset atomic swap on Lightning mainnet. Attendees will leave with a concrete understanding of how cross-L2 atomic swaps work in practice, the open problems that still need solving, and a mental model for building on Bitcoin's emerging liquidity layer.
Paid APIs with Lightning
- Time
- Thu, Oct 1 · 12:45 PM – 1:15 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 30m
APIs power the modern internet, but monetizing them still depends on subscriptions, API keys, and centralized billing systems. Bitcoin Lightning and the L402 protocol introduce a different model: APIs that can charge per request natively over the internet. In this talk, I’ll introduce ngx_l402, an open-source NGINX module written in Rust that enables Lightning-powered API authentication and monetization using HTTP 402. We’ll explore pay-per-use APIs, AI inference endpoints, and machine-to-machine payments with Lightning, along with lessons learned building ngx_l402.
Creating a Cashu Wallet with CDK
- Time
- Thu, Oct 1 · 1:45 PM – 2:45 PM
- Location
- Talks Stage
- Type
- workshop
- Duration
- 1h
The goal of this workshop is to help participants understand the Cashu protocol and how it works, as well as to create and implement a Cashu wallet using the CDK (Cashu Dev Kit) library. Participants will implement a wallet that communicates with a Cashu Mint, performs the token mint process, exchanges tokens with other participants, and melt them.
Fedimint
- Time
- Thu, Oct 1 · 3:30 PM – 4:00 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 30m
The talk will summarize the lessons from three years of developing a federated Chaumian mint and relate them to an update on recent technical developments and new deployments.
Zcash-Style Private Payments on Bitcoin L1
- Time
- Fri, Oct 2 · 11:45 AM – 12:30 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 45m
In this talk, [[alloc] init] introduces Shielded Bitcoin, a new metaprotocol for Zcash-style private payments on Bitcoin L1 without a soft fork, trusted operators, separate consensus network, or reliance on client-side state for recovery. Shielded Bitcoin uses encrypted notes, nullifiers, and zero-knowledge proofs to preserve the privacy of transaction participants, amounts, and transfer relationships, while using Bitcoin for canonical publication, ordering, and settlement. Misha will explain how Bitcoin PIPEs enable this architecture through covenants, non-interactive ZK-proof verification, and cryptographically controlled L1 vaults — and explore the broader design space this opens for payment metaprotocols on Bitcoin.
Speakers
Bitcoin's FX Layer
- Time
- Fri, Oct 2 · 12:30 PM – 1:00 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
Examine the technologies and opportunities behind cross-currency payments on Bitcoin using Lightning.
Lightning Payments Proven in Zero-Knowledge
- Time
- Fri, Oct 2 · 1:00 PM – 1:45 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 45m
Zerosats is an early-stage experiment in making Bitcoin transactions private while keeping the base chain maximally transparent. A useful analogy is that Zerosats aims to be for Bitcoin what a VPN is for HTTP - a "Bitcoin VPN" for its users. The prevalence of Lightning payment providers shaped the protocol's core requirement: it must connect to the Lightning Network to allow fast and final settlement. Establishing that connection in a trust-minimized, non-custodial way required implementing timelocks, a key component of Hash Time Locked Contracts (HTLCs) and a fundamental primitive for both cross-chain atomic swaps and Lightning payment routing. HTLCs normally depend on a timelock supplied by the underlying blockchain. In private, zero-knowledge settings no such timelock is available inside the circuit, which forces reliance on trusted sequencers or external oracles. To make the Lightning connection viable, we introduce a method for constructing verifiable timelocks inside zero-knowledge circuits by reusing Bitcoin's accumulated proof-of-work as a computational reference clock. We describe the protocol, discuss its security margins, and report preliminary benchmarks for the proving cost of the resulting circuits.
Speakers
Silent Payments - BlindBits balance between UX and privacy
- Time
- Fri, Oct 2 · 1:45 PM – 2:30 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 45m
I would like to talk about Silent Payments and BlindBit. Silent Payments should be known by now. BlindBit is my software suite that I've created around Silent Payments. It consists of several components: - An indexer - A couple of personal scanner projects of which one, friglet, can also be combined with Sparrow as a drop-in replacement for Frigate - Basic spending wallets (mobile, cli, desktop gui) This software suite has been around for several years. Over the years I have been tackling the UX and privacy problems around Silent Payments from several angles and have been trying to balance the two. This is supposed to be the core of my talk. So it will combine a journey through the UX challenges and how they were tackled in history. How BlindBit has tried new ideas to improve UX and privacy for users. About the title, I'm not sure if it should focus on the "journey to fix SP UX" or simply the "balancing UX vs. privacy" part. No matter the title, the content does not really change in essence. Concepts and Frameworks around Silent Payments (Indexing, Scanning and Spending). In general, what we would like to do, depending on the audience, is: - Do a recap of Silent Payments and the cryptography around it, or at least the basic components of how the keys and outputs are derived - Talk about the scanning issue and how we can tackle it with different approaches: always-on scanning, public high-performance scanning, ad-hoc local scanning on device, and external scanning Several tricks can be used to make scanning more efficient and to improve the UX for users. All angles have trade-offs and would like to show how BlindBit works around those. I held a talk at "le paradigme bitcoin" in Neuchâtel, about BlindBit, and will link the presentations pdf. The talk was directed at a non-technical audience but it conveys what topics can be tackled around BlindBit and Silent Payments. Link to slide deck: https://github.com/setavenger/presentation-le-paradigme-2026/blob/master/deck.pdf
Speakers
Project Loupe - AI powered security scanning for Bitcoin OSS Projects
- Time
- Fri, Oct 2 · 5:30 PM – 6:15 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 45m
We will present the Loupe architecture and learnings we gathered after 5 months of scanning.
Can Bitcoin Payments Survive the AI Onslaught?
- Time
- Fri, Oct 2 · 6:15 PM – 7:00 PM
- Location
- Main Stage
- Type
- panel
- Duration
- 45m
Bitcoin has suffered a series of serious vulnerability exploits in the last few weeks, thanks to increasing capabilities from the AI/LLM models. In this panel, we invite industry and payment veterans to weigh in on whether the open source payments are feasible in the face of increasingly persistent and intelligent adversaries.
smite: snapshot fuzzing for lightning
- Time
- Fri, Oct 2 · 11:45 AM – 12:30 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 45m
This past year, I have been contributing to smite, a new fuzzing framework for lightning by Matt Morehouse. In this talk, I will share my experience with it and with getting into fuzzing in general.
Cashu payments made simple
- Time
- Fri, Oct 2 · 1:00 PM – 1:45 PM
- Location
- Talks Stage
- Type
- workshop
- Duration
- 45m
In this workshop, I’ll show you how to integrate Cashu and Lightning payments into any web app using Coco in just a few minutes. Coco is a batteries-included Cashu framework I’m building to make getting started with Cashu effortless.
Linky - send bitcoin like a message
- Time
- Fri, Oct 2 · 1:45 PM – 2:30 PM
- Location
- Talks Stage
- Type
- workshop
- Duration
- 45m
Linky is a cashu wallet that allows people to send bitcoin just like messages. The recipient does not even need the app at first. Build the bitcoin network with your friends by frequent payment interactions. At the workshop, you will be able to try everything out for yourself, discuss and discover additional features.
Hackathon: Project expo
- Time
- Fri, Oct 2 · 3:30 PM – 5:00 PM
- Location
- Talks Stage
- Type
- hackathon
- Duration
- 1h 30m
First round of judging for the hackathon projects
Speakers
Hackathon: Judges meeting
- Time
- Fri, Oct 2 · 5:00 PM – 5:30 PM
- Location
- Talks Stage
- Type
- hackathon
- Duration
- 30m
Private meeting for judges.
Speakers
The return of magic internet money
- Time
- Sat, Oct 3 · 11:30 AM – 12:00 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
Arkade, sapio and Liquid enable some cool, totaly random, epic op_codes that let you build all kinds of interesting things. And with work being done on GSR and Simplicity, maybe some of this magic will one day make it into Bitcoin. So let’s explore the crazy things you could build if you had access to every op_code you could dream of. Let’s see what unhinged magical things this internet money can really do.
Accountable Chaumian Ecash
- Time
- Sat, Oct 3 · 12:00 PM – 12:30 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
Chaumian ecash enables a centralised mint to issue tokens that its users can transact with. These transactions are private, in the sense that the mint cannot link a token that it receives from a payee with a token it issued to a payer. However, existing ecash constructions all assume the mint to be trusted. In particular, the mint is assumed not to secretly overissue tokens (a so-called slow rug). In this talk, I'd like to present an ecash protocol that protects users from overissuance, while preserving unlinkability, through the use of Schnorr Proofs-of-Knowledge. Every token will be accompanied by such a proof to guarantee the corresponding blinded message is present in a public list of issued tokens.
Speakers
Payments for Miners With P2Poolv2 Share Chain
- Time
- Sat, Oct 3 · 12:30 PM – 1:00 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
P2Poolv2's share chain supports Bitcoin Script and provides a bitcoind compatible JSON API. The talk will cover how on-chain swaps and off-chain swaps with LN, Ark and even Cashu can be used to pay miners on p2poolv2.
It Worked on My Node
- Time
- Sat, Oct 3 · 1:00 PM – 1:30 PM
- Location
- Main Stage
- Type
- talk
- Duration
- 30m
What actually happens when you accept Bitcoin payments
Hackathon: Finals
- Time
- Sat, Oct 3 · 1:30 PM – 2:30 PM
- Location
- Main Stage
- Type
- hackathon
- Duration
- 1h
Finals presentation for the hackathon
What Should the Next Bitcoin Payment Stack Look Like?
- Time
- Sat, Oct 3 · 3:00 PM – 4:00 PM
- Location
- Main Stage
- Type
- panel
- Duration
- 1h
With the launch of Arks, Glass Coins, Shielded Bitcoin -- the bitcoin payments space is as crowded as ever. Where is the future of payments for Bitcoin headed?
Tap that Cash: Building Cashu Payment Terminals with Nucula
- Time
- Sat, Oct 3 · 11:30 AM – 12:30 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 1h
Learn about building low-cost Cashu payment terminals using embedded hardware like the ESP32. The talk takes you through the development from basic cryptography to fully integrated Tap-to-Pay UX on dedicated, open-source hardware. Want to contribute to the firmware or roll your own? Connect a peripheral like a vending machine? We will cover it all!
Triggering Lightning: Building Event-Driven Payouts
- Time
- Sat, Oct 3 · 12:30 PM – 1:00 PM
- Location
- Talks Stage
- Type
- workshop
- Duration
- 30m
Lightning is uniquely suited to automated, event-driven payments. This talk walks through the architecture of an open, self-hostable system that turns web events into Lightning payouts while keeping the node, the keys, and the liquidity entirely yours.
Your Lightning Simulation Is Lying to You
- Time
- Sat, Oct 3 · 1:00 PM – 1:30 PM
- Location
- Talks Stage
- Type
- talk
- Duration
- 30m
If you want to test a routing change, a fee policy, or an attack, you can't do it on mainnet, so you do it on a synthetic graph. The problem is that the standard generators don't produce graphs that look like the Lightning Network. Last year I published a comparison of Erdős–Rényi, Barabási–Albert, Watts–Strogatz, and a disassortative BA variant against a mainnet snapshot (11.5k nodes, 41.5k channels). Every one of them misses at least one property that matters for routing: hubs, negative degree mixing, or clustering. I'll go through where each model breaks and why, then show new, not-yet-published results on a simple model that gets all of them right. I'll finish with a short demo of Maestro, the Rust testbed I built to run these experiments: real CLN and LND nodes on whatever topology you feed it, with seeded, replayable payment traffic. Looking for collaborators.
Speakers