Quantum cryptography is a branch of cryptography that leverages principles of quantum mechanics to provide secure communication between parties. Here are a few examples of quantum cryptography algorithms:
Quantum Key Distribution (QKD): QKD is one of the most well-known quantum cryptography algorithms. It allows two parties, traditionally referred to as Alice and Bob, to establish a secure symmetric encryption key known only to them. The security of the key distribution relies on the laws of quantum mechanics, making it resistant to eavesdropping or interception.
BB84 Protocol: The BB84 protocol is a specific implementation of quantum key distribution. It was proposed by Charles H. Bennett and Gilles Brassard in 1984. In this protocol, Alice prepares a stream of quantum bits (qubits) in one of four possible states, representing the two bits of a cryptographic key. Alice randomly encodes the bits using two mutually unbiased bases, and Bob measures the received qubits using the same or randomly chosen bases. Through public discussion and error checking, Alice and Bob can extract a secure key from the matching measurement results.
E91 Protocol: The E91 protocol, also known as Ekert protocol, was proposed by Artur Ekert in 1991. It utilizes the phenomenon of entanglement to distribute a secure key between two distant parties. Alice and Bob share pairs of entangled particles, typically photons, and perform measurements on their respective particles. By comparing a subset of their measurement results and applying classical error correction techniques, they can obtain a secure key.
B92 Protocol: The B92 protocol, proposed by Bennett in 1992, is another quantum key distribution scheme. It uses single photons and employs quantum states to represent the bits of a cryptographic key. Similar to the BB84 protocol, Alice prepares the photons in one of two non-orthogonal states, and Bob randomly measures the photons using a compatible basis. By exchanging information about the bases used, Alice and Bob can establish a secure key.
These are just a few examples of quantum cryptography algorithms. Quantum cryptography is a rapidly evolving field, and new algorithms and protocols are being developed to enhance security and efficiency in quantum communication.