Supporting ₿uildΞrs with sweat and capital. Managing Partner @masterkeyvc. Co-Founder of: @Web3_devs @israelcryptoio @icryptoforum
Crypto universe
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Saul (Shauli) Rejwan retweeted
The best kind of meetup:
When the audience creates as much value as the speakers.
Over the course of last night's meetup, audience members kept both speakers going with sharp technical questions on address reuse, 2FA vs on-chain keys, and co-signers vs custodians.
🎤 @_benkaufman built a live 2-of-3 Bitcoin multisig with a Ledger, Trezor and Jade: xpubs, descriptors, on-device address checks, a PSBT signed by two keys.
His rule: back up the descriptor, or two keys won't be enough to spend.
🎤 @boazeb took it to mobile. After a recent iOS zero-day leaked seeds from phones, he asked if multisig is inevitable for consumer wallets.
His @summocash wallet runs 2-of-3 with a policy-checking co-signer and guardian recovery.
See you at the next one!
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If you’re using AI, make sure your agent knows how to operate multisig well
Hands-on workshop in person and online by our top community members:
@_benkaufman for Bitcoin wallets and @boazeb for EVM wallets
Bring your laptops and favorite wallets
@Ledger @Trezor @Blockstream
TOMORROW NIGHT
Wed. 23 September | 6:00 PM
📍 LIVE at @sncentral_, 28 Lilienblum St. Tel Aviv
→ @_benkaufman workshops multisig with @SparrowWallet.
→ @boazeb on building @summocash, his 2-of-3 multisig app.
Refreshments will be served 🍻🍕
luma.com/o6gh384v
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We will stream it online as well
NEXT MEETUP IN TEL AVIV
1. @_benkaufman workshops multisig with @SparrowWallet.
2. @boazeb on building @summocash, his 2-of-3 multisig app.
🗓️ Wednesday - 23/9/2026
📍@sncentral_ (28 Lilienblum St.)
Learn to keep your crypto safe: luma.com/o6gh384v
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Agreed.
But let’s be honest most founders don’t have the privilege to choose all of their backers, but all should ask portfolio companies and advisors who they are brining into their family.
tldr Get a venture investor who puts themselves on the line for you.
As a founder, you sacrifice your life, your identity, your peace of mind, and more, for a decade or longer.
Venture investors, by definition, have a portfolio. As a consequence, they are not as single mindedly committed to your startup as you are.
However, that doesn’t mean they can’t be invested.
And by investment, I don’t mean capital. That’s cheap and easy, especially today.
I mean:
- their brand
- their time
- their networks
- their reputation
You want someone on your side who’s willing to lay it all on the line for you. To speak for you in rooms you’re not in. To pick up the phone at 11pm at night or 3am in the morning.
Capital is the cheapest thing an investor can give you. Ask for the expensive stuff.
Before signing a term sheet, please reference check the person (not just the firm) with other startups to see
what, besides capital, they’ve put on the line.
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Saul (Shauli) Rejwan retweeted
Is Your Bitcoin Safe? ColdCard's RNG Failure and How Not to Lose It All nitter.net/i/broadcasts/1rGmqqPvB…
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Saul (Shauli) Rejwan retweeted
🚨 Emergency session THIS WEDNESDAY.
A build error from March 2021 made COLDCARD wallets generate seeds from software instead of the hardware RNG.
The seeds ended up with just 40 bits of entropy instead of 128. Attackers have now taken around 1,816 BTC (~$114M) from ~5,294 addresses.
Speakers:
- @AvishaiY, Co-Founder & CEO at @sodabubblelabs
- @boazeb, ex. @Citi, ex-CEO Blocktrail/BTC.com
- @SHAP0W, Managing Partner at @MasterkeyVC
On the agenda:
- what exactly went wrong
- how to check if your wallet is affected, and what to do next
- why nobody caught it for five years
📅 Wed, Aug 5
🕐 12:00 EDT · 18:00 CET · 19:00 IDT
📍 Live on X, YouTube & LinkedIn: luma.com/web3devs-nc1e
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Saul (Shauli) Rejwan retweeted
A simplified explanation of the Coldcard issue.
When you set up your Coldcard it generates a secret - the words it tells you to copy and keep safely. Turns out it was choosing those words in an easily predictable way (instead of randomly), meaning it’s easy to guess which words a Coldcard would choose.
Since it’s easy to guess your secret, anyone can know it. This secret is the key to your Bitcoin - meaning anyone who guesses the secret has as much ownership of the Bitcoin as you do, and can steal it to a wallet they control.
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“Life isn't about waiting for the storm to pass; it is about learning to dance in the rain”
Happy crypto winter 🕺🏻
"If you're in crypto, pivot to AI."
I used to hear versions of this, and it's the wrong way to think about the world. It's zero sum, scarcity thinking.
Crypto is a general purpose technology. It's infrastructure, the same way electricity or the internet is infrastructure. It doesn't compete with the next big thing, because it underpins it. It's an *and*, not an *or*.
AI being a megatrend takes nothing away from crypto. If anything, it makes crypto more important.
AI agents will need their own financial infrastructure and will eventually transact far more per day than all humans combined. They can't open a bank account, they can't wait three days for a wire, they reside in one country. They need real time programmable money (and that's crypto).
Agents will need to hold funds and pay for things on their own. We pioneered this with the x402 protocol, Base, and USDC, which now power the vast majority of all agentic payments. Agents will also engage in trading and act as a financial advisor. They will raise or borrow money for new projects they are undertaking. They will eliminate tasks for us around tax planning, portfolio rebalancing, and bill pay.
Welcome to the world of Agentic Finance (AiFi). This is what Coinbase is building.
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"Too big to fail" is the phrase Bitcoin was invented in response to. Today it's the question being asked about Bitcoin itself, moderated by a banker.
Lee Counselman of @Barclays with @SHAP0W of @MasterkeyVC, Evgeny Gokhberg of @Re7Capital, @Dgt10011 of @Paraficapital, and @stutireal of @PanteraCapital.
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If Global Liquidity Tightens, What Actually Survives in Crypto?
Crypto has largely matured during a period of abundant liquidity. But what happens when capital becomes harder to access?
At InnovateMiami, @JamesKibbie (@GalaxyHQ), @nsheikhy (G20 Group), @SHAP0W (@MasterkeyVC), and @AmarOdedra (@AlgoFoundation / @Algorand) discussed which assets, business models, and markets are built to endure.
Moderated by @alemartcard (@foundationcap).
Watch the full panel now: piped.video/_xZdExgK8fQ
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Saul (Shauli) Rejwan retweeted
Agents on a Leash | Web3 Devs underground nitter.net/i/broadcasts/1wGWjjABB…
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Saul (Shauli) Rejwan retweeted
AI agents are signing transactions, holding keys, and moving real funds, usually with no guardrails at all.
That's a brand-new attack surface, and your current security model wasn't built for it.
Join us THIS WEDNESDAY for a deep technical session on securing autonomous agents, with Kevin Jones (@cryptomastery_), founder of @1clawAI and DevRel at @edgeandnode / @graphprotocol.
What we're covering:
• Why AI agents are a new class of attack surface
• Giving an agent a leash (policy enforcement), a wallet (HSM-backed key custody), and a safety belt (pre-execution guardrails)
• How @1clawAI secures the agent economy at scale
• Practical patterns for builders shipping agents that touch real funds
🗓 Wednesday, June 17
🕔 17:00 IDT | 16:00 CET | 10:00 EDT
📡 Live on X, YouTube & LinkedIn
If you're building or deploying onchain AI agents, this one goes straight to the core.
Register: luma.com/web3devs_undergroun…
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RT @Web3_Devs: Quantum Money Special nitter.net/i/broadcasts/1dGYllLLW…
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Saul (Shauli) Rejwan retweeted
Two years ago, we started with a simple question. What will it take to simplify the integration of blockchain primitives with global financial rails?
Today we’re launching LI.FI Intents to help make that possible for every business in the world.
A product we know this industry needs, a product we’ve built to solve some of the biggest challenges global fintechs face as they move into digital assets, a product we believe companies don’t need tomorrow, or even today, they needed it yesterday.
How do we enable stablecoin payments?
How do we unlock access to real-world assets for our users?
How do we ensure we only touch compliant liquidity across blockchains?
These are some of the biggest questions leadership teams across fintech are asking themselves right now.
They’re the same questions we asked ourselves. And we knew they had to be solved.
LI.FI Intents is our answer.
Every touchpoint of the stack is modular. The entire product is fully customizable to fit ANY business need.
From the order type, to who the market maker can be, to how the transaction will be settled on blockchains, to which service providers your business trusts - everything can be shaped around how you want your product to work.
As a builder myself, this is the kind of flexibility and abstraction I’ve been looking for in this industry ever since we started LI.FI 5 years ago.
And I’m incredibly proud that the LI.FI team is delivering it.
LI.FI Intents is built to make crypto products easier to launch for businesses that want to move onchain, but have been slowed down by the complexity of it all.
The enterprise stack for onchain finance.
For all intents and purposes.
Introducing LI.FI Intents.
Infrastructure for apps, wallets, and neobanks to:
• Enable stablecoin payments
• Access real-world assets
• Tap into compliant onchain liquidity
Built for enterprises bringing financial products onchain.
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Top builders are in…
.@FarroYossi says " Every single venture firm should have an office in Israel."
"I think one person really missing out on Israel right now is @a16z."
"I'm calling out a16z. I think you guys should open up a venture firm in Israel this year."
"Shabbat Shalom."
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Saul (Shauli) Rejwan retweeted
.@FarroYossi says " Every single venture firm should have an office in Israel."
"I think one person really missing out on Israel right now is @a16z."
"I'm calling out a16z. I think you guys should open up a venture firm in Israel this year."
"Shabbat Shalom."
Breaking: A16Z is opening an office in Japan this summer, making Tokyo the firm’s only international office.
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Saul (Shauli) Rejwan retweeted
We’re pleased to welcome @SHAP0W , Managing Partner at @masterkeyvc , as a speaker at the Tokenized Capital Summit 2026 in Miami 🇺🇸
Shauli will share how emerging ecosystems are identified before they break out - covering founder-market fit, timing cycles, and how capital is positioned ahead of narrative shifts in crypto.
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Saul (Shauli) Rejwan retweeted
We are excited to invite you to join us for another Web3 Devs Underground event!
🔐₿ Two sessions. Two frontiers. One event.
@Web3_Devs × @zama x @RitrekRecovery
powered by @MasterkeyVC
📅 March 11th | 17:00 Israel Time | 16:00 CET | 10:00 EDT
📍 Live on X, YouTube & LinkedIn
Register Here: luma.com/78qezjr0
Session 1 - FHE & Confidential Smart Contracts
@poppyseedDev (Aurora Poppyseed), DevRel at @zama, breaks down how Fully Homomorphic Encryption (FHE) is bringing real confidentiality to the EVM - running computations on encrypted data without ever decrypting it.
From private transfers to blind auctions, this is what on-chain privacy actually looks like.
Session 2 - TimeLock Recovery for Bitcoin Backup
@oren_z0 (Oren Zomer), Founder at @RitrekRecovery, walks through structured wallet recovery using Bitcoin Script - primary to secondary wallet, and what BIP-128 makes possible.
Self-sovereign custody, done right.
Two of the most technically dense topics in crypto infrastructure - in one session.
Whether you're building on EVM or working with Bitcoin Script, this one's for you.
🔗 See full calendar: lnkd.in/dPBqaEMc
@MasterkeyVC @SHAP0W @Amit_Masterkey @Web3_Devs @ELuttenberg789 @AlonKivity @al23xyz #Web3 #Bitcoin #FHE #Zama #ZeroKnowledge #BitcoinScript #Cryptography #Web3Dev #Blockchain #DeFi #SmartContracts #MasterkeyVC
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