# Shor's Algorithm Peter Shor's 1994 quantum algorithm for factoring large integers exponentially faster than any known classical method. The single most consequential quantum algorithm because it breaks RSA encryption — the mathematical foundation of most internet security, financial transactions, and classified communications. RSA security depends on the assumption that factoring the product of two large prime numbers is computationally infeasible for classical computers. Shor's algorithm exploits [[Quantum Computing]]'s ability to find the period of a function using quantum Fourier transforms, converting the factoring problem into one that a quantum computer can solve efficiently. A quantum computer with enough stable [[Qubit]]s running Shor's algorithm could factor RSA keys in hours that would take classical computers millions of years. The practical threat is not yet here — current quantum computers lack the qubit count and coherence to factor cryptographically relevant numbers. But the theoretical result drives the entire [[Post-Quantum Cryptography]] transition and the [[Harvest Now Decrypt Later]] intelligence strategy. The question is not whether Shor's algorithm works (mathematically, it does) but when quantum hardware will be powerful enough to run it on real-world keys. ## See Also - [[Quantum Computing]] — the hardware required - [[Post-Quantum Cryptography]] — the defense being built - [[Harvest Now Decrypt Later]] — the intelligence strategy Shor's algorithm enables - [[Technology Lexicon]] — the full vocabulary (quantum computing section)