ETSI GR QSC 006 V1.1.1 Quantum-Safe Cryptography (QSC); Limits to Quantum Computing applied to symmetric key sizes

Analyses how long symmetric ciphers and hash functions remain secure against quantum attack using Grover's algorithm. It models an optimistic commercial quantum computer around 2050 and an idealised worst-case machine, accounts for error-correction and parallelisation overheads, and concludes that 256-bit keys such as AES-256 should stay safe well beyond 2050, while advising industry to find and plan to replace products relying on 128-bit or shorter keys.

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