Monthly Meetup of the Web3 Developers Underground community

Web3 Devs Underground - Monthly Meetup 🔐 Multisig in Practice | Sparrow Workshop + Building summo.cash Your keys. Your coins. But can you actually prove it — and ship it? This session goes deep into Bitcoin multisig from two angles: a hands-on hardware wallet workshop, and a live look inside a multisig product being built in production. Whether you're securing your own stack or building for others, this one is for you. 🎙 Brought to you by Israel Web3 Developers Underground × Startup Nation Central Powered by Masterkey VC Date & Time 📅 Wednesday, September 23rd, 2026 Time: 18:00 - 21:00 Location: Startup Nation Central, Tel Aviv Speakers Talk 1 — "Sparrow Wallet Multisig Workshop" 🎤 Ben Kaufman, Open Source Developer @ Synonym A hands-on walkthrough of setting up a multisig wallet using Sparrow — including hardware wallet integration, key coordination, and signing flows. You'll leave knowing exactly how to do this yourself. Setting up a multisig quorum from scratch in Sparrow Pairing and verifying hardware signers step by step Signing flows, PSBT handling, and what to check before funds go in Common pitfalls and how to avoid them Talk 2 — "Building summo.cash: A 2-of-3 Multisig App in Production" 🎤 Boaz Bechar, Open Source Developer @ papervault.xyz A look inside summo.cash — a 2-of-3 multisig application actively in development — covering architecture decisions, UX tradeoffs, and what it takes to ship a multisig product users can actually use. Hot, warm, and cold wallets — the real differences and what they mean for key management Why 2-of-3 and how quorum selection affects your threat model Building multisig UX that doesn't terrify users Lessons from shipping a real multisig product Agenda: 18:00 - 18:30 | Drinks and Networking 18:30 - 18:40 | Opening Remarks 18:40 - 19:25 | Ben Kaufman — Sparrow Wallet Workshop 19:25 - 19:35 | Q&A with Ben 19:35 - 19:45 | Break for Food and Drinks 19:45 - 20:30 | Boaz Bechar — Building summo.cash 20:30 - 20:40 | Q&A with Boaz 20:40 - 21:00 | Finish the evening with us over a beer and some small talk. About Our Sponsor: Masterkey Venture Capital is a global early-stage fund investing in top-tier innovative deep tech and Web3 infrastructure projects. With a strategic presence in key crypto hubs worldwide, we are uniquely positioned to drive technological advancements within global ecosystems. Backed by nearly 50 years of combined expertise in advanced infrastructure, novel cryptography, cybersecurity, and energy solutions, our team is dedicated to empowering the entrepreneurs shaping the future of blockchain technology. Get Involved Interested in Speaking or Sponsoring? We welcome passionate individuals and organizations to contribute to our community. If you're interested in speaking at future events or sponsoring our meetups, please fill out the Speaker application form and contact Amit Shilo at @AmitShilo (Telegram) Community Team: Amit Shilo, Eden Luttenberg, Alon Kivity, Alon Ben Lavy, Ariel Wagowsky, David Langellotti, Boaz Bechar, Daria Nik. Founded by Shauli Rejwan and Roy Osherove. RSVP Now! Join the Israeli branch. Register Here Limited seats are available. Register early to ensure your participation! Stay Connected Website Linktree Telegram Stay in the loop (socials): Twitter – /Web3Devs YouTube – https://www.youtube.com/@web3devsunderground/streams Calendar – https://lu.ma/web3devsunderground See You There!