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by sdevlin 3845 days ago
AES (and other symmetric ciphers) are vulnerable to Grover's algorithm (https://en.wikipedia.org/wiki/Grover%27s_algorithm), which effectively cuts key sizes in half. AES-128 would be reduced to 64-bit security. This isn't a big problem in practice, since we can just switch to 256-bit ciphers like AES-256 and ChaCha20.

Public-key schemes based on factoring and discrete logarithms are undone by Shor's algorithm (https://en.wikipedia.org/wiki/Shor%27s_algorithm), but there are asymmetric systems not known to be vulnerable to quantum algorithms. They are less mature, but researchers are working it.

There's some good high-level information at http://pqcrypto.org/ and in this paper: http://pqcrypto.eu/docs/initial-recommendations.pdf.