abstract
- Quantum Key Agreement (QKA) is a current research topic within quantum cryptography where two or more parties collaboratively generate a shared secret key, commonly without individual full control of it. This work proposes a QKA method involving a third party other than the transmitter and receiver. Based on an initial BB84 procedure as in the EBB84 protocol, participants create an indefinite key, which becomes strong against multiple intercept-resend attacks. The process does not need decoy photons as in many other QKA protocols. Security improvements against eavesdropping are observed as compared with the BB84 protocol. The proposal could be designed to reach eavesdropping failure probabilities of 516 on average and fidelities lower than 14 for the modified state during the attack. The simplicity of the proposed protocol allows its implementation for more than two participants with current technology for the protection of information. Overall, it gives an understanding of the process used to share secured information between several parties without a previous agreement. © Published under licence by IOP Publishing Ltd.