  Quantum key agreement requires all participants to recover the shared key
together, so it is crucial to resist the participant attack. In this paper, we
propose a verifiable multi-party quantum key agreement protocol based on the
six-qubit cluster states. A verifiable distributor who preserves some
subsequences of the six-qubit cluster states is introduced into this protocol,
thus the participants can not obtain the shared key in advance. Besides, the
correctness and simultaneity of the shared key are guaranteed by the trusted
design combiner and homomorphic hash function. Furthermore, the security
analysis shows that the new protocol can resist the external and internal
attacks.
