In this paper we present a new, two-centered electronic voting scheme that is capable of preserving privacy, universal verifiability, and robustness. An interesting property of our scheme is the use of double encryption with additive homomorphic encryption functions. In the two-centered scheme, the first center decrypts the ballots, checks the eligibility of the voters, and multiplies each eligible vote, which is still encrypted in the cryptosystem of the second center. After the deadline is reached, the second center obtains the final tally by decrypting the accumulated votes. As such, both centers cannot know the content of any individual vote, as each vote is hidden in the accumulated result, therefore the privacy of the voters is preserved. Our protocols, together with some existing protocols, allow everyone to verify that all valid votes are correctly counted. We apply the r-th residue cryptosystem as the homomorphic encryption function. Although decryption in the r-th residue cryptosystem requires an exhaustive search for all possible values, based on experiments we show that it is possible to achieve desirable performance for large-scale elections.