Today's encryption (RSA, ECC) relies on math problems that are hard for classical computers. "What are the factors of this 2048-bit number?" A regular supercomputer would take 1 Billion years. A Quantum Computer (with enough Qubits) could do it in minutes.
Harvest Now, Decrypt Later
Nation States are currently recording ALL encrypted traffic they can intercept.
They store it in massive data centers.
They can't read it today.
But in 2035, when they build a Quantum Computer, they will decrypt all the secrets from 2025.
1. Post-Quantum Cryptography (PQC)
NIST has selected new algorithms (CRYSTALS-Kyber) that are resistant to Quantum attacks.
Apple has already deployed PQ3 in iMessage to protect against this future threat.
2. QKD (Quantum Key Distribution)
Using physics to transmit keys.
If a spy tries to intercept the photon, the quantum state collapses, and the receiver knows they are being watched.
It provides theoretically perfect security.