Kvantvõtmi

Kvantvõtmi, often translated as quantum key distribution (QKD), is a method of secure communication that uses quantum mechanics to generate and distribute cryptographic keys. Unlike traditional cryptography, which relies on mathematical complexity to secure information, QKD leverages the fundamental laws of physics to ensure that any attempt to eavesdrop on the key exchange will be detected.

The most common QKD protocols, such as BB84, involve sending photons, the particles of light, encoded with quantum information. These photons are transmitted from a sender (Alice) to a receiver (Bob) through a quantum channel, typically optical fiber or free space. The polarization or phase of the photons is manipulated to represent binary bits (0s and 1s).

A key principle of QKD is the no-cloning theorem, which states that it is impossible to create an identical copy of an arbitrary unknown quantum state. If an eavesdropper (Eve) tries to intercept and measure the photons to learn the key, she inevitably disturbs their quantum state. Alice and Bob can then detect this disturbance by comparing a subset of their transmitted and received bits over a public channel. If the error rate exceeds a certain threshold, they know the key has been compromised and discard it.

Once the secure key is established through QKD, it can be used for symmetric encryption, a method where the same key is used for both encrypting and decrypting messages. This ensures that the subsequent communication remains confidential and tamper-proof. QKD is a fundamental building block for future quantum-secure networks.