What is elliptic-curve cryptography?

Public-key cryptography based on a hard problem about points on a curve. It protects most web traffic and Bitcoin.

Elliptic-curve keys are much shorter than RSA keys for the same strength, a 256-bit key against a 3072-bit one, so they are faster and now more common. Most HTTPS connections use them to agree on a session key, and Bitcoin uses them to sign transactions.

Shor’s algorithm breaks elliptic curves too, and needs fewer qubits to do it than for RSA-2048, because the keys are shorter.

RSAA public-key encryption method from 1977 whose security relies on how hard it is to factor the product of two large primes.
Shor's algorithmA quantum algorithm, published by Peter Shor in 1994, that factors large numbers and breaks the encryption most of the internet uses for key exchange and signatures.
Post-quantum cryptographyEncryption that runs on ordinary computers and is designed to resist attacks by quantum computers.
Q-DayThe day a quantum computer can break the public-key encryption in wide use today, such as RSA-2048 or 256-bit elliptic curves.