Secure multiparty computation is one focus in the international cryptographic community in recent years. The private computation of multisets is also of great practical significance. In order to privately compute on multisets

we first propose two new encoding schemes. Then based on Paillier probabilistic encryption algorithm

we design three simple and efficient secure two party protocols to compute the intersection

the union and the summation of two private multisets. We prove that they are secure in the semi-honest model. We also analyze the computational complexities and communication complexities of the protocols and test the efficiency on a PC. The test result shows that our protocols are efficient.