Cambridge Spent 11 Years Stress-Testing Bitcoin – Here’s What They Found in Their Research

A comprehensive eleven-year study by the Cambridge Centre for Alternative Finance has found that the Bitcoin network demonstrates remarkable resilience against failures in the physical internet infrastructure, including submarine cables. The research indicates that Bitcoin can withstand the simultaneous failure of up to 92% of the world's submarine cables before the network experiences significant disruption. In fact, 87% of real-world cable faults over the past decade caused less than a 5% disruption to Bitcoin nodes.

Network Resilience Explained

The study, which analyzed eight million node observations and 658 submarine cables, found that most cable failures have a negligible impact on the Bitcoin network. During a significant cable failure event in March 2024 off Côte d’Ivoire, which severed seven to eight cables and reduced regional internet capacity by 43%, only five to seven Bitcoin nodes globally were affected, representing a mere 0.03% of the network. Researchers attribute this resilience to the network's layered architecture, where failures in the physical layer (cables) do not automatically cascade to the routing or Bitcoin peer-to-peer layers. The increasing adoption of Tor, with around 64% of reachable nodes using it by 2026, further enhances resilience by routing traffic through obfuscated pathways less susceptible to physical cable geography.

Identified Vulnerabilities

Despite its robustness against physical infrastructure failures, the study identifies two primary vulnerabilities. The first is the potential for targeted attacks on high-traffic cables, which could significantly lower the failure threshold. The second, and more pressing concern for 2026, lies in the concentration of the network's routing layer within five major cloud providers: Hetzner, OVHcloud, Comcast, AWS, and Google Cloud. Regulatory pressure or coordinated action against these providers could lead to a 10% network disconnection, a scenario far more plausible than widespread physical cable sabotage.

The Quantum Computing Threat

Looking further ahead, the study addresses the long-term threat posed by quantum computing. Quantum computers could potentially break ECDSA, the digital signature system used to prove Bitcoin ownership, while SHA-256, which secures mining, is more resistant. An estimated 4 to 7 million BTC are currently considered vulnerable, particularly early coins where public keys were exposed on the blockchain. While a practical quantum attack is believed to be at least a decade away, requiring an estimated 2,330 logical qubits compared to current hardware's ~100 usable qubits, nation-state actors are reportedly already recording blockchain data for future decryption. Bitcoin Improvement Proposal (BIP)-360, a quantum defense measure, has been merged into the codebase, and companies are developing quantum-resistant signature schemes, though challenges remain in integrating these larger signatures into Bitcoin's block structure.