Definition. An attack strategy in which encrypted communications are intercepted and stored at scale today, to be decrypted at a future point once a sufficiently powerful quantum computer becomes available. The attack is passive and leaves no trace; it makes classical asymmetric encryption (RSA, ECDH) retroactively insecure.

Why relevant. Data with long confidentiality requirements — contracts, patient records, key material, internal communications — is already at risk today, even if the actual attack is still years away. Migrating to hybrid post-quantum schemes (ML-KEM in the TLS handshake) is the only technical countermeasure.

Related.Post-Quantum Cryptography, ML-KEM, Crypto Agility