How can encrypted votes be aggregated without revealing individual ballots?

Conditions

• All ballots are encrypted before submission.
• Aggregation is performed on encrypted data.
• Only final totals are revealed.

Reasoning, step by step

1. Collect all encrypted ballots (envelopes) from the voters.
2. Use a protocol to aggregate the results inside all the envelopes without revealing particularly each vote.
3. Reveal only the sum for each candidate.
4. Ensure that the individual votes remain hidden and cannot be recovered from the aggregate result.

Example

The speaker explains that at the end we use a protocol to aggregate the results inside all the envelopes without revealing particularly each vote, and only reveal the sum. In the example, the public output would be the number of votes for blue and the number of votes for red.

Common misconceptions

• Assuming individual encrypted votes can be opened separately: One might assume that after submission, an authority could decrypt one ballot at a time, whereas in the described protocol, decryption is only available after aggregation.

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