How Exposed Are Ethereum and Solana to a Potential Quantum Threat?

Project Eleven’s 2026 report finds material quantum-exposure for major smart-contract chains: roughly 65% of Ethereum holdings sit in addresses using quantum-vulnerable primitives (ECDSA, BLS, KZG), while Solana is structurally 100% vulnerable because its Ed25519 public-key model embeds public keys in addresses. A successful quantum attack against validator BLS keys could enable forged attestations, mass slashing and consensus disruption. Markets face a binary risk: technological breakthroughs could force rapid post-quantum migrations and re-price protocol security premia, while planned mitigations (Ethereum’s post-quantum hub and target L1 upgrades by 2029; Solana clients adopting NIST-approved Falcon) reduce, but do not eliminate, near-term threat. Project Eleven models Q-Day as possibly arriving as early as 2030 (optimistic), with alternative scenarios in 2033 and 2042, leaving investor sentiment cautious and focused on upgrade timelines and migration readiness.