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The exact multiplicative complexity of counting votes. Ren é Peralta Yale University 2004. Thanks to: Michael Fischer Joan Boyar Ivan Damgaard…. Basic voting protocol (referendum mode). registration authority emits unforgeable and untraceable ballots.
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The exact multiplicative complexity of counting votes. René Peralta Yale University 2004 Thanks to: Michael Fischer Joan Boyar Ivan Damgaard…
Basic voting protocol (referendum mode). • registration authority emits unforgeable and untraceable ballots. • voters cast sealed votes into public bulletin board. • counting program decides, announces, and proves outcome.
OUTCOME? • exact count. • whether motion passes. • something in between …
It may be desirable to reveal no other information. • coercion. • vote buying and selling.
Circuit computing a function of votes Encrypted votes
x4 x1 x1 x3 x3 x4 x5 Å Å Å Å x2 x1 x4 x5 Å Å x2 x2 Å L L L Motion passes by majority vote
outcome of circuit with encrypted inputs is revealed by a discreet proof (BDP)
The length of a discreet proofis linear in the number of (mod 2) multiplications in the circuit. ADDITIONS are free!
Multiplicative complexity. any Boolean function can be represented by a circuit using only addition and multiplication modulo 2. Multiplicative complexity is the number of multiplications necessary and sufficient.
(Shannon, Lupanov) : almost all Boolean functions on n variables have gate complexity about (BPP 98): Multiplicative complexity over the basis(Å, L, 1)is about 2n n-1 q (2n/2)
NOT MUCH ELSE IS KNOWN!
We focus on concrete multiplicative complexity. For symmetric functions of the votes, computing the Hamming weight is central to this problem.
RESULT (Boyar, Peralta) . The multiplicative complexity of computing the Hamming weight of n bits is exactly n – H(n) e.g. if n = 37 = 100101 then the optimal circuit contains 34 multiplications.