The whole election process using the Prêt à Voter system can be divided into the following six stages:

• Set-up stage: During this stage, the election parameters are set. The parameters should include the eligible criteria for all involved parties such as candidates, voters and election authorities, and also some rules for ballot validation, ballot casting and ballot tallying. Then the election authorities for registration, ballot construction and ballot tallying are selected, followed by eligible candidates registering themselves. Afterwards, all these parameters, the candidates and authorities are made public.
• Registration stage: During this stage, voters should register themselves with the registration authorities. Their eligibility is determined by the criteria published in the previous stage, where ineligible voters are not allowed to register and participate in voting. Finally, a list of registered eligible voters is made public for verification.
• Ballot Construction Stage: ballots are generated by ballot generation authorities in this stage. Generally, we require the number of ballots generated to be more than twice the number of eligible voters. Afterwards, some third parties are allowed to randomly challenge some of these ballots to check they are correctly constructed. If no cheating is detected, the remaining ballots are allowed to be used in the election. Otherwise, if any cheating is detected, all of these ballots will be destroyed and this stage will be restarted after replacing the ballot generation authorities.
• Voting Stage: The voting stage is the only phase to cast votes. Only eligible registered voters are allowed to cast their votes. At first, they need to be authenticated by the registration authorities according to the list published in the set-up stage, and those who are not found in the list are not allowed to vote. As follows, each authenticated voter will be provided with a ballot form (it is suggested that each authenticated voter will receive two empty ballot forms, they can randomly challenge one ballot and then fill in and cast the other one). The voters have to cast their votes in a secure place, such as a voting booth. Finally, all received ballots are mixed or aggregated in order to break the voter-vote links.
• Tallying Stage: In this stage, ballots from the previous stage are processed to obtain the final result. First, all ballots from the voting stage are collected. Then every ballot is verified according to the criteria published in the set-up stage, where only valid ballots are included for tabulation. Finally, all valid ballots are opened and counted, and the final result is then revealed and made public.
• Auditing Stage: The purpose of the auditing stage is to ensure that the election authorities have performed correctly in both the voting stage and the tallying stage. In this stage, every voter can check that her vote has been properly included in the final tally and all recorded votes have been tallied correctly and her vote is one of them. Besides, any interest party can verify the correctness of the final result.

The election authorities are involved in the whole election processes. In order to make the introduction more clear, we have classified all election authorities into three groups according to different roles:

• Ballot generation authorities: before the election, all the ballot forms are generated by these authorities.
• Registration authorities: they have two major responsibilities: one is to validate the eligibility of voters, making sure that only eligible voters are allowed to vote. The other is to sign the voter's receipt.
• Ballot tallying authorities: they are in charge of decrypting the received votes which are valid and publish the final result.

When the election authorities have been selected, all these election authorities have to work together to prepare the set-up stage. In this stage, the major work is to set-up the election parameters, such as defining the election rules, validating the election candidates, and making the criteria clear who are eligible to vote. Besides, each of the ballot tallying authorities (tellers) has to generate two public key pairs. They have to publish the public keys and prove they know the corresponding secret keys. And then they have to distribute their secret keys among all other tellers in a threshold fashion. The registration authorities have to generate a public key pair in a threshold fashion and make the public key known to the public. The corresponding secret key is used to sign the voter's receipt.

In the registration stage, only registration authorities are involved. When voters register themselves to the election, the registration authorities have to evaluate the eligibility of each voters according to the criteria. Only eligible voters are allowed to be registered. Afterwards, a list of all eligible voters will be published.

In the ballot construction stage, the ballot generation authorities first collect the public keys published by ballot tallying authorities. Then all ballots are constructed. The number of ballot forms generated in this stage should be more than twice the number of eligible voters. Afterwards, some third party can randomly challenge some of the ballots and if any cheating is detected, all these ballots will be destroyed and the ballot construction stage will be restarted after replacing the ballot generation authorities.

All election authorities might be involved in the voting stage. The registration authorities have to ensure that only eligible voters are allowed to cast votes. They provide each eligible voter with two ballots (it is suggested that two ballots are printed on the same card, one on each side of the card). Each voter can randomly challenge one ballot and use the other one to cast her vote. The voters can either require the ballot generation authorities to show how the ballots are constructed or they can check whether the ballots can be correctly decrypted by the ballot tallying authorities. Voter's vote (maybe along with the voter's name) will be published on to a bulletin board. In the Prêt à Voter system, each voter will be provided with a receipt. In order to solve dispute, the receipt has to be signed by the registration authorities before it was taken out of the voting booth. And each voter should check whether the signature is valid. If not, she can accuse immediately.

In this stage, the ballot tallying authorities will first collect all received votes from the bulletin board. Then the validity of each vote is examined by the ballot tallying authorities according to the criteria. It has to be publicly verifiable which votes have be eliminated from the final tally and the reason why they have been removed. Finally, the result will be announced after all valid votes are decrypted by these authorities using mix network.

In the auditing stage, every voter can audit whether her vote has been correctly recorded. The voters can compare their receipts with the bulletin board. If their receipts are correctly displayed by the bulletin board, their votes are correctly recorded. Otherwise, if they cannot find their receipt on the bulletin board, they can challenge the registration authorities to some trusted third parties. Their proof is the receipt which has been signed by the registration authorities.

Also, any interested party can audit whether the final result has been tallied correctly. In the Prêt à Voter system, auditing the ballot tallying stage is achieved using Randomised Partial Checking, in which auditors can randomly challenge some of the decryption done by the ballot tallying authorities. In order to protect voter's privacy, no complete voter-vote link is allowed to be revealed.

In an election using the Prêt à Voter system, voters will be involved in the registration stage, the voting stage and the auditing stage. In the registration stage, each voter just need to use some of her identity proof, such as passport and drive license, to prove that she is an eligible voter. And we have introduced how ordinary voters can audit the election. In this section, we will focus on how the voters cast their votes.

Firstly, we will briefly introduce the ballot form in the Prêt à Voter system. Once a voter have been authenticated in the voting booth, she will be provided with a blank ballot as shown in the Figure below:
Example Ballot Form

The form consists of two columns with a perforation in the middle. The left hand column contains the candidate list. The order is randomly permuted and varies among different ballots, thus it is infeasible to predict the candidate order of a certain ballot form. The right hand column against each candidate is left blank for you to make your choice. On the right hand column, there is also some secret information which can be used to re-construct the candidate list if properly decrypted. The Prêt à Voter system can handle both binary voting method and ranked voting method, each voter can either mark against her preferred candidate(s) or give a preference ranking of a partial or all of the candidates, as shown here:
Second Figure

In order to cast votes property, the voters should follow the following rules:

1. If the election is using binary voting method, voters just need to mark against their preferred candidate(s). If the election is using ranked voting method, voters should give their preference to all or partial of the candidates by marking No. 1 against the first choice candidate, No. 2 against the second choice candidate, and so on. (Note that some elections have several races, and they may use both methods for different races)
2. Then the ballot form need to be separated along the perforation between the two columns. The left hand column of the ballot form has to be destroyed in the voting booth. If the left hand column is seen by others except the voter, this voter's privacy will be violated.
3. Finally, the voter should submit her right hand column of the ballot to the registration authorities, they will scan her vote, sign it and return a receipt to the voter. Then this voter can take the receipt home.