✨ Range Chaum-Pedersen proofs are needed to efficiently support cumulative voting

[eionblanc]

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Suggestion

Toward the initial goal of supporting cumulative voting, range Chaum-Pedersen proofs (encrypted plaintext is one of 0, 1, ..., or limit) generalize disjunctive Chaum-Pedersen proofs. When range Chaum-Pedersen proofs are used for both selection encryption limits and contest limits (replacing constant Chaum-Pedersen proofs there), they render placeholder selections unnecessary and in turn are more efficient (fewer exponentiations required for ballot encryption of all contest types, not just cumulative voting; submitted file size reduction).

Possible Implementation

Proof components will generalize to lists/arrays and eradicate the hard-coded zero- and one- proof components. Placeholder selections and their infrastructure will be removed.

The nuance between votes allowed for a particular selection and votes allowed across a contest (in sum) will be reflected in the code; meanwhile, this can amend the current conflation between number_elected and votes_allowed.

Anything else?

See this pull request with the corresponding schema changes.