🔢 Shor's Factoring Algorithm

Exponential quantum speedup that threatens modern cryptography

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Grover's Search Algorithm

💥 The Cryptography Breaker

In 1994, Peter Shor discovered a quantum algorithm that shook the cryptography world. While classical computers need exponential time to factor large numbers, Shor's algorithm does it in polynomial time. This threatens RSA encryption, which protects most of today's internet communications.

🚨 The RSA Problem

RSA encryption relies on one key fact: factoring large numbers is hard. It's easy to multiply two primes (e.g., 61 × 53 = 3,233), but extremely hard to factor the result back. A 2048-bit RSA key would take classical computers billions of years to crack. Shor's algorithm could do it in hours.

RSA-768 (232 digits)
2 years
Classical record (2009)
RSA-2048 (617 digits)
Billions of years
Current standard
With Shor's
Hours
On quantum computer

🌟 Why It's Revolutionary

  • Exponential Speedup: First practical quantum algorithm with exponential advantage over classical
  • Cryptographic Impact: Breaks RSA, Diffie-Hellman, and elliptic curve cryptography
  • Quantum Fourier Transform: Introduces QFT, now used in many quantum algorithms
  • Post-Quantum Era: Drove development of quantum-resistant encryption standards

🔑 Key Components

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Period Finding

Find the period of modular exponentiation using quantum parallelism

🌊

Quantum Fourier Transform

Extract period from superposition through phase estimation

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Classical Reduction

Convert period-finding to factoring using number theory

Polynomial Time

Runs in O((log N)³) time versus exponential classical time