Multicast key negotiation method suitable for group calling system and a system thereof

A multicast key negotiation method suitable for a group call system, comprising:

• a) negotiating a unicast key between a UT and a BS, deriving an information encryption key and an integrity check key from the unicast key, and registering by the UT to the BS identifiers of service groups to which the UT pertains;
• b) notifying, by the BS, the UT of multicast keys of service groups to be applied by the UT, constructing a multicast key notification message which comprises a service group key application list and a message integrity check value, and sending the multicast key notification message to the UT, wherein the service group key application list, which is a ciphertext obtained by encryption using the information encryption key, comprises identifiers and the multicast keys of the service groups to be applied by the UT;
• c) decrypting, by the UT, the service group key application list on receiving the multicast key notification message sent by the BS to obtain the multicast keys of the service groups to be applied by the UT, constructing a multicast key confirmation message which comprises a service group key response list and the message integrity check value, and sending the multicast key confirmation message to the BS, wherein the service group key response list, which is a ciphertext obtained by encryption using the information encryption key, comprises the identifiers of the service groups which have been applied;
• and
• d) confirming, by the BS, that the multicast keys of the service groups for the UT have been established successfully upon the multicast key confirmation message sent by the UT.