Quantum computers do not threaten the security of 128-bit symmetric keys in AES-128 and SHA-256 according to technical analysis of Grover's algorithm and its implementation constraints.

Grover's algorithm delivers a quadratic speedup requiring π/4 × √N invocations of the oracle for search space N but the oracle must execute sequentially within a quantum circuit and parallelization by partitioning the keyspace degrades the speedup Zalka 1997 Filippo Valsorda 2024. Concrete costing for a 128-bit key partitioned across 2^16 quantum instances raises total work from 2^64 to 2^72 operations making the attack more expensive than classical brute force on equivalent classical hardware.

NIST IR 8105 Report on Post-Quantum Cryptography 2016 and the NIST PQC standardization process focus resources exclusively on replacing RSA ECDH ECDSA and EdDSA while stating no changes are required for AES or SHA key lengths NSA CNSA 2.0 guidance 2022 aligns with this position as does Bernstein's cryptanalysis survey 2021 identifying what prior media coverage omitted the non-parallelizable nature of oracle calls and the massive error-corrected qubit overhead estimated in excess of 10^6 logical qubits for AES-128 Grover attacks.

Patterns from IBM and Google quantum hardware roadmaps 2023-2024 show cryptographically relevant machines remain decades away for symmetric attacks reinforcing that post-quantum investment must target asymmetric primitives only.