Fireside Chat with Charles on Post Quantum World I Charles Guillemet & Kartik Talwar

Sat, May 2, 2026, 12:00 AM

In this fireside chat, Kartik Talwar interviews Charles Guillemet, CTO of Ledger, on the post-quantum cryptography landscape and its implications for blockchain security. Charles traces his journey from heading Ledger's security department (the "Dungeon") to becoming CTO, and explains how Ledger's operating system approach has allowed them to support the rapidly expanding blockchain ecosystem since 2017. He provides a detailed breakdown of quantum computing threats, explaining how Shor's algorithm can theoretically break elliptic curve cryptography and how Google's recent paper reduced the required qubits from a million to 41,000. The conversation covers the two main post-quantum signature approaches — hash-based (well-studied but larger signatures) and lattice-based (smaller, faster but newer) — and the challenge of reaching social consensus in decentralized networks like Bitcoin and Ethereum to agree on migration timelines and standards. Charles also discusses AI's impact on security, noting that attack costs are trending toward zero, and outlines Ledger's vision for agentic payments using hardware-enforced delegation policies that give AI agents fine-grained spending permissions without exposing private keys. 00:00 Introduction 00:10 Welcome and Charles Guillemet Introduction 01:13 From Chief Security Officer to CTO 03:09 How Custody Has Evolved Since 2017 04:40 Ledger's OS Approach to Supporting New Chains 05:43 Traditional Finance Discovering Blockchain 06:06 How Real Is the Quantum Computing Threat 07:30 Shor's Algorithm and Google's Recent Breakthrough 08:57 Why Migration Matters More Than Timelines 09:53 NIST Standards and 2030/2035 Deadlines 10:44 The Social Consensus Challenge for Bitcoin and Ethereum 12:20 Google's Paper: 41,000 Qubits for Elliptic Curves 13:23 Hash-Based vs Lattice-Based Post-Quantum Signatures 15:13 Address Migration and Transition Challenges 16:43 What Happens to Unmigrated Coins 17:17 Ledger's Approach to AI Agents and Payments 18:15 AI Changing the Security Paradigm 19:10 Why Agents Will Default to Crypto Payments 19:35 Hardware-Enforced Delegation Policies for Agents 21:00 What's Next: Security, AI, and Formal Verification 22:46 Closing _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 🇫🇷 *Pragma Cannes 2026* Pragma Cannes 2026 was held on April 2nd at the JW Marriott Hotel in Cannes, France and was an in-person summit for builders and leaders in the web3 ecosystem. Watch the full Pragma Cannes 2026 YouTube Playlist here: https://www.youtube.com/playlist?list=PLXzKMXK2aHh5OnsJ95gz7HoI1tLUj3kZr ETHGlobal's Pragma series takes place in cities around the world, and is designed to be a different kind of event. Pragma is a one-stage conference with founders-only on stage, bringing together a small group of curated attendees and speakers to discuss the future of web3 and reflect on the past. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ✅ Follow Charles Guillemet X: https://x.com/P3b7_ ✅ Follow Ledger X: https://x.com/ledger ✅ Follow Kartik Talwar X: https://x.com/TheRealKartik ✅ Follow ETHGlobal X: https://x.com/ETHGlobal​ Warpcast: https://warpcast.com/ethglobal Website: https://ethglobal.com YouTube: https://www.youtube.com/@UCfF9ZO8Ug4xk_AJd4aeT5HA _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Are you interested in Ethereum development and entrepreneurship? 👉 Sign up for the next ETHGlobal event: https://ethglobal.com/events 🎁 Get exclusive access and perks with ETHGlobal Plus! https://ethglobal.com/plus 📣 Want us to throw an event in your city? Tell us where! https://ethglobal.com/city