A class of multiparty key agreement protocols based on secret sharing is presented. The trust infrastructure necessary to achieve the intended security goals is discussed. Entity authentication is suggested to be replaced by a less expensive group authentication. Two key agreement protocols are discussed. The first is the group key agreement where all principals must be active to call the conference. The other allows a big enough subgroup (controlled by the threshold parameter t) to trigger the conference. It is proved that the protocols achieve key freshness, key confidentiality, group authentication and key confirmation. A discussion about possible modifications and extensions of the protocol concludes the paper.