Quantum third party secures secret sharing from collusion attacks
Collusion-Secure Semi-Quantum Secret Sharing Scheme using a Quantum Third Party
Cryptography and Security
Summary
Secret sharing lets a group split a secret so that only certain groups can reconstruct it. In some versions, participants have limited quantum ability, which can let dishonest players team up with a quantum assistant to cheat and reveal the secret. The authors designed a new method where even if dishonest participants or the quantum helper try to collude, they can’t learn the secret without being caught. This approach improves security while making the process more efficient and practical for classical users with a quantum helper.
What this means in practice
- •For quantum communication engineers: Integrate a secure semi-quantum secret sharing protocol that resists collusion between classical participants and the quantum server using simple Bell states.
- •For cybersecurity teams: Strengthen multi-party secret sharing involving constrained classical devices by preventing undetectable collusion attacks with quantum-assisted protocols.
Authors
Santanu Majhi, Nirupam Basak
Abstract
The security of a secret sharing protocol is compromised if one or more dishonest participants can reconstruct the secret by deviating from the prescribed protocol, particularly when such malicious behavior remains undetected. Semi-Quantum Secret Sharing (SQSS) is a variant of secret sharing in which the participants possess only classical capabilities, such as preparing and measuring qubits in the computational ($Z$) basis, while a quantum-capable third party assists the dealer in generating and distributing quantum shares of a classical secret. The limited quantum capabilities of the participants in SQSS protocols may introduce vulnerabilities to collusion attacks, enabling an assisting quantum third party, in collaboration with a dishonest classical participant, to jointly recover the secret even without detection. In this work, we propose a novel SQSS protocol that eliminates this vulnerability and achieves information-theoretic security against collusion attacks. We further prove that the proposed protocol is secure against a broad class of external and internal attacks. Finally, a comparative analysis demonstrates that our construction advances existing SQSS protocols by simultaneously optimizing qubit efficiency, involves a classical dealer, and resilience against DCNA attacks using basic Bell states.