In order to solve the problem that two tenants required to fair share equijoin size in management-type SaaS (software as a service),both a combinational formula of equijoin size and a share protocol of encrypted data equijoin size across private database were proposed.The universal set of 2-tuple was sent to the other tenant by service provider,which was constituted by a sharing attribute value and a hash values of others attributes to corresponding tuple.After the sharing attribute value of 2-tuple was re-encrypted,tenant sent them to the other.Both the ciphertext intersection of sharing attribute and the number of each element corresponds to tuples were calculated by tenant independently.By the combinational formula of equijoin size,the equijion size was fairly shared between tenants.The integrity and security showed that the share protocol of equijoin size was perfect and safe in the semi-honest model.By the efficiency analysis,the computation and communication costs were 50% and about 68% of those in utilizing the fair sharing information by Agrawal’sprotocol. It met the basic needs of management-type SaaS by prototype testing.
