mirror of
https://github.com/saymrwulf/swisspost-evoting-go-poc.git
synced 2026-05-14 20:58:03 +00:00
saymrwulf
e8b6f30871
Proof-of-concept reimplementation of the Swiss Post e-voting cryptographic protocol in Go. Single binary, 52 source files, 2 dependencies. Covers ElGamal encryption, Bayer-Groth verifiable shuffles, zero-knowledge proofs, return codes, and a full election ceremony demo.
50 lines
1.1 KiB
Go
50 lines
1.1 KiB
Go
package elgamal
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import (
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emath "github.com/user/evote/pkg/math"
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)
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// Encrypt computes the ElGamal encryption of a message.
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// gamma = g^r
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// phi_i = pk_i^r * m_i
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func Encrypt(msg Message, r emath.ZqElement, pk PublicKey) Ciphertext {
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if msg.Size() != pk.Size() {
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panic("message size must match public key size")
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}
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group := pk.Group()
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g := group.Generator()
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// gamma = g^r
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gamma := g.Exponentiate(r)
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// phi_i = pk_i^r * m_i
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phis := make([]emath.GqElement, msg.Size())
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for i := 0; i < msg.Size(); i++ {
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pkR := pk.Get(i).Exponentiate(r)
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phis[i] = pkR.Multiply(msg.Get(i))
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}
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return Ciphertext{
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Gamma: gamma,
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Phis: emath.GqVectorOf(phis...),
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}
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}
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// EncryptOnes encrypts an all-ones message (used for trivial ciphertexts).
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// gamma = g^r, phi_i = pk_i^r
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func EncryptOnes(r emath.ZqElement, pk PublicKey) Ciphertext {
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group := pk.Group()
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g := group.Generator()
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gamma := g.Exponentiate(r)
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phis := make([]emath.GqElement, pk.Size())
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for i := 0; i < pk.Size(); i++ {
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phis[i] = pk.Get(i).Exponentiate(r)
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}
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return Ciphertext{
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Gamma: gamma,
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Phis: emath.GqVectorOf(phis...),
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}
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}
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