Why Post-Quantum Cryptography Now? Classical public-key cryptography (RSA, ECDH) relies on mathematical problems that are hard for classical computers — factoring large integers or solving the discrete logarithm problem. A sufficiently powerful quantum computer running Shor’s algorithm could solve these problems efficiently, breaking all existing RSA and ECC-based security. Quantum computers capable of breaking 2048-bit RSA don’t exist yet. But “harvest now, decrypt later” attacks are real: adversaries intercept and store encrypted traffic today, planning to decrypt it once quantum computers mature.