can you suggest any applicayion for implementing threshold homomorphic encryption cryptosystem(Paillier cryptosystem) I want to implement one project in multi party homomorphic encryption using paillier. Can you suggest any application for implementation.
How about this: an electronic voting scheme. Votes are cast onto a publicly readable but append-only bulletin board as encryptions under the system public (Paillier) key. Anyone can homomorphically compute the sum of the cast votes. The vote admins each hold a share in the secret key; they must cooperate in order to decrypt anything. In this way, as long as there is one honest administrator, he can ensure that only the correct ciphertext (the one corresponding to the sum of all votes and not the vote of any one individual) is decrypted.

Basically, this boils down to the CGS scheme (link) but for Paillier encryption. Furthermore, you will want to use zero-knowledge proofs tailored for Paillier threshold decryption and encryption; these are presented in the paper by Damgård and Jurik (link).

Another suggestion is this: multi-party computation for calculating not just the sum of some private inputs, but for calculating any function of the private inputs while keeping those inputs themselves hidden. The BeDOZa protocol (link) explicitly covers using Paillier encryption for the offline part (precomputation phase), even though all values in the online part (actual computation phase) are information-theoretically private.