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Quantum Encryption’s Hidden Weakness Exposed by New Eavesdropping Attack

Researchers at the School of Physics and Astronomy have unveiled a new eavesdropping technique called Manipulate-and-Observe that targets the classical reconciliation phase of quantum key distribution (QKD). By intercepting between 0% and 11% of photons and injecting subtle errors, the attack exploits parity‑leakage in protocols such as BB84 combined with Cascade error correction, shrinking the key search space from 2ⁿ possibilities to a single candidate. Simulations show the method can fully recover the secret key, exposing a critical weakness in the post‑processing stage despite the quantum channel’s theoretical security. The findings urge a reassessment of reconciliation algorithms and broader system‑level security proofs for QKD deployments.