Post-quantum cryptography
AES
Advanced Encryption Standard
The standard symmetric block cipher used for bulk encryption. AES is not broken by quantum computers: Grover's algorithm gives only a square-root speedup, so AES-256 remains secure and AES-128 remains adequate for most uses.
Related terms
Symmetric cryptography
Cryptography where the same secret key both encrypts and decrypts. It is far less affected by quantum computing than public-key cryptography — Grover's algorithm only halves the effective key strength.
Grover's algorithm
A quantum search algorithm that finds an item in an unstructured set of N in roughly √N steps. Against symmetric cryptography this halves effective key strength — a nuisance answered by doubling key sizes, not a break.