Abstract: The controlled quantum key agreement (CQKA) protocol requires a controller to oversee the process of all participants negotiating a key, which can satisfy the needs of certain specific scenarios. Existing CQKA protocols are mostly two-party or three-party, and they do not entirely meet the actual needs. To address this problem, this paper proposes new CQKA protocols based on Bell states and Bell measurements. The new CQKA protocols can be successfully implemented for any N-party, not just two-party. Furthermore, the security and efficiency analyses demonstrate that the new CQKA protocols are not only secure but also more efficient in terms of quantum bit.

Key words: quantum cryptography, quantum key agreement, controlled quantum key agreement, Bell states, controller