BB84 Protocol
What is BB84 Protocol?
BB84 ProtocolThe first quantum key distribution protocol, proposed by Bennett and Brassard in 1984, which encodes random bits on photon polarization states.
BB84, introduced by Charles Bennett and Gilles Brassard in 1984, is the canonical quantum key distribution protocol. Alice transmits a stream of single photons polarized in one of four states drawn from two non-orthogonal bases (rectilinear and diagonal), each encoding a random bit. Bob measures each photon in a random basis; over a public authenticated channel they later announce their basis choices and discard mismatched rounds. The remaining bits form the raw key. Any eavesdropper inevitably introduces a quantum bit error rate above a known threshold because measuring an unknown state disturbs it. After error correction and privacy amplification, Alice and Bob hold an information-theoretically secure shared key.
● Examples
- 01
Encoding bit 0 as a horizontally polarized photon and bit 1 as a vertically polarized photon in the rectilinear basis.
- 02
Detecting an eavesdropper because the quantum bit error rate exceeds about 11 percent.
● Frequently asked questions
What is BB84 Protocol?
The first quantum key distribution protocol, proposed by Bennett and Brassard in 1984, which encodes random bits on photon polarization states. It belongs to the Cryptography category of cybersecurity.
What does BB84 Protocol mean?
The first quantum key distribution protocol, proposed by Bennett and Brassard in 1984, which encodes random bits on photon polarization states.
How does BB84 Protocol work?
BB84, introduced by Charles Bennett and Gilles Brassard in 1984, is the canonical quantum key distribution protocol. Alice transmits a stream of single photons polarized in one of four states drawn from two non-orthogonal bases (rectilinear and diagonal), each encoding a random bit. Bob measures each photon in a random basis; over a public authenticated channel they later announce their basis choices and discard mismatched rounds. The remaining bits form the raw key. Any eavesdropper inevitably introduces a quantum bit error rate above a known threshold because measuring an unknown state disturbs it. After error correction and privacy amplification, Alice and Bob hold an information-theoretically secure shared key.
How do you defend against BB84 Protocol?
Defences for BB84 Protocol typically combine technical controls and operational practices, as detailed in the full definition above.
What are other names for BB84 Protocol?
Common alternative names include: Bennett-Brassard 1984, BB84 QKD.
● Related terms
- cryptography№ 891
Quantum Key Distribution (QKD)
A method that uses quantum-mechanical properties of photons to let two parties share a secret key while detecting any eavesdropper on the channel.
- cryptography№ 465
Harvest Now, Decrypt Later
An attack strategy where adversaries record encrypted traffic today to decrypt it once cryptographically relevant quantum computers become available.
- cryptography№ 846
Post-Quantum Cryptography
Classical cryptographic algorithms designed to remain secure against attacks by both classical and large-scale quantum computers.
- cryptography№ 244
Cryptographic Agility
The property of a system that lets it replace cryptographic algorithms, parameters, or keys quickly and safely when threats or standards change.