A quantum algorithm is a computational procedure designed for quantum computers, using qubits, quantum gates, superposition, and entanglement before measurement produces classical results. Quantum computers are not general-purpose replacements for classical machines; their advantage depends on the problem. section 14.1.2
In cryptography, the important consequences are:
- Shor’s algorithm finds periods efficiently, enabling efficient solutions to factorization and discrete logarithm problems. section 14.1.3
- Those results threaten RSA, Diffie–Hellman, and elliptic-curve cryptography because they depend on factorization or discrete logarithms. section 14.1.3
- Increasing public-key parameters is described as impractical: quantum-resistant RSA was estimated to require one-terabyte parameters. section 14.1.3
A cryptographic warning
Data encrypted today with RSA or elliptic curves and stored for years could become decipherable once capable quantum computers exist, creating a long-term confidentiality risk. section 14.1.3
