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

- Speakers: Charles Guillemet, [Kartik Talwar](https://streameth.org/speakers/kartik-talwar)
- Channel: [ETHGlobal](https://streameth.org/ethglobal)
- Date: 2026-05-09
- Duration: 22:57
- Topics: Ledger, post-quantum cryptography, quantum computing, Charles Guillemet, Kartik Talwar, Pragma, Shor's algorithm, elliptic curve, NIST, hash-based signatures, lattice-based signatures, Bitcoin, Ethereum, blockchain security, AI agents, agentic payments, delegation, hardware wallet, secure enclave, formal verification, zero knowledge, qubits, Google, migration, custody, CTO, Dungeon, operating system, smart contracts, Web3, DeFi, institutional finance, private keys, seed phrase, governance
- Watch: https://streameth.org/watch/yt-_9dAoM6WyGI
- YouTube: https://www.youtube.com/watch?v=_9dAoM6WyGI

## Description

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

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🇫🇷 *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. 

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✅ 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 

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