Q1. Privacy Preserving Secure Models

Privacy Preserving Online Voting System

Recently, several controversies have been observed in voting around the world. Even electronic voting can be manipulated1. In an electronic voting system, the voting authority cannot be trusted completely as it can be biased. Using a privacy-preserving online voting system removes controversy in the voting system. In this privacy-preserving online voting system, voters encrypt their votes in the voting booth before sending them to the voting authority. A voting server records each encrypted vote and determines the voting result on behalf of the voting booth as the voting booth does not have enough computation power. The encrypted result is sent to the voting authority, which determines the winner based on encrypted votes. The homomorphic property of the Paillier Cryptosystem allows the addition of encrypted numbers. Therefore, the Paillier Cryptosystem can be used in developing a privacy-preserving online voting application.

In this task, you need to design a privacy preserving online voting system as shown in Figure-1 using the Paillier cryptosystem. Suppose that a group of students want to elect their club president.

Your designed privacy-preserving voting application must fulfil the following requirements:

• Votes must be encrypted from Voting Booth using Paillier Cryptosystem before sending them to the Voting Server.

• A vote is an integer number which should be equivalent to a 12-bit binary string.

• The number of candidates should be three. For example, ALICE, BOB, and EVE.

• The number of voters can be maximum 16.

• Assume that four voters will vote for ALICE, two voters will vote for BOB, and two voters will vote for EVE. after counting the votes, the Voting Authority (VA) should find four votes for Alice, two votes for BOB, and two votes for EVE.

• The Voting Authority chooses p=157, q=127 and select g=8821.

• The private numbers chosen by 8 voters and their votes are as follows:

• The Voting Authority sets up required public and private keys and makes the public-keys to all voting booth before the vote starts.

Show detail step-by-step computations of the key generation, encryption, homomorphic computations, and decryption processes for votes of 8 voters.