A Guide to Post-Quantum Cryptography

Summary: Trail of Bits explains that Shor's algorithm, developed by Peter Shor in 1994, runs integer factorization in polynomial time and would break RSA and all discrete log-based public key cryptography, including elliptic curves, if a quantum computer were built. Grover's algorithm inverts functions in O(√n) time, reducing AES-256 to 128 bits of security and 256-bit hash preimages to 2^128, which the post calls not a serious threat to symmetric cryptography since doubling security is not burdensome.
Why it matters: Every widely used public key cryptosystem in production today falls to one algorithm, and NIST's post-quantum standardization process was still reviewing first-round submissions when this was written - so the migration clock is running against an adversary who can collect ciphertext now and decrypt it later.

Read the original at Trail of Bits Blog ↗