Steal Now, Reveal Never: The Quiet Arrival of Quantum Attacks

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Speaker: Jon Stephens, Shankara Pailoor

Type: Talk

Expertise: Some familiarity with the topic

Event: Devcon

Date: Nov 2026

Post-quantum migration in blockchains is often reduced to a simple story: a cryptographically relevant quantum computer appears, elliptic-curve signatures fail under Shor's algorithm, and a post-quantum replacement is deployed. The reality is far more complex. Quantum capabilities are likely to emerge gradually and behind closed doors, leaving defenders uncertain whether an adversary has already crossed the threshold. Rather than causing an immediate collapse, early quantum advantage may enable selective, difficult-to-detect attacks against wallets, bridges, validators, exchanges, and custodians. Drawing on years of auditing security-critical blockchain systems, this talk explores how these attacks could unfold, which architectural assumptions fail first, and why meaningful migration requires rethinking transaction models, consensus, custody, privacy, and ownership rather than simply replacing digital signatures.