  A multi-party quantum key distribution protocol based on repetitive code is
designed for the first time in this paper. First we establish a classical (t,
n) threshold protocol which can authenticate the identity of the participants,
and encode the classical key sequence in accordance with this repetitive code.
Then unitary transformation of the quantum state sequence corresponding to this
encoded sequence is carried out by using the parameters from this (t, n)
threshold protocol. Furthermore, we derive two thresholds for whether or not
reserving the measured values of the received sequence, and extract the
classical subkey sequence from the measured values conforming to these two
threshold conditions. This protocol can authenticate the identity of the
participant, resist the attack from the internal and external participants, and
do not need the decoy state particles when testing the eavesdropper, which is
more efficient than the similar protocols, and also saves the quantum
resources.
