EN|FREN|FRModern systems rely on asymmetric (RSA, ECDSA, Diffie-Hellman) and symmetric (AES, ChaCha20) cryptography. Quantum computing introduces Shor's algorithm (breaks RSA, DH, ECC) and Grover's (weakens symmetric keys). The main impact is on public-key cryptography, not on hashes or AES-256.
Post-quantum cryptography (PQC) runs on classical computers and resists both classical and quantum attacks. It is not quantum cryptography (QKD): PQC is software-based, standardised by NIST, and is the primary migration path for most organizations.
Today's quantum computers are NISQ-era: limited qubits, high error rates. Breaking RSA-2048 is not possible today; no known quantum computer compromises real-world TLS or VPN. PQC migration is a strategic move, not an emergency. Preparation matters because migrations are slow and long-term confidentiality matters.