Using GHZ-State for Multiparty Quantum Secret Sharing Without Code Table

We proposed two multiparty quantum secret sharing schemes based on n-particle Greenberger-Horne-Zeilinger-states (GHZ states), which are transformed from Einstein-Podolsky-Rosen pairs by entanglement swapping. In our schemes, the dealer imposes messages by performing local unitary operations (I, sigma x, i sigma y, sigma z) on the n-particle GHZ state she holds, and the agents collaborate to deduce the dealer's messages by performing local unitary operations on their own qubit. The amount of dealer's secret message is positively related with the number of agents. The need of qubits is one-third less than the former schemes and, also, they can be reused for the next new round. The scheme (II) does not have to pre-share the code table, which increases the security without the risk of being stolen.