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https://github.com/saymrwulf/swisspost-evoting-go-poc.git
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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.
38 lines
1.1 KiB
Go
38 lines
1.1 KiB
Go
package mixnet
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import (
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"github.com/user/evote/pkg/elgamal"
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emath "github.com/user/evote/pkg/math"
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)
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// Shuffle holds the result of a re-encrypting shuffle.
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type Shuffle struct {
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Shuffled *elgamal.CiphertextVector // C' shuffled ciphertexts
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Perm Permutation // π permutation used
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Rho *emath.ZqVector // ρ re-encryption exponents
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}
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// GenShuffle performs a re-encrypting shuffle on ciphertexts.
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// C'_i = Enc(1; rho_i, pk) * C_{pi(i)}
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func GenShuffle(cts *elgamal.CiphertextVector, pk elgamal.PublicKey) Shuffle {
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n := cts.Size()
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zqGroup := emath.ZqGroupFromGqGroup(pk.Group())
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perm := GenPermutation(n)
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rhoElems := make([]emath.ZqElement, n)
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shuffled := make([]elgamal.Ciphertext, n)
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for i := 0; i < n; i++ {
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rhoElems[i] = emath.RandomZqElement(zqGroup)
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// Enc(1; rho_i, pk)
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enc := elgamal.EncryptOnes(rhoElems[i], pk)
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// C'_i = enc * C_{pi(i)}
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shuffled[i] = enc.Multiply(cts.Get(perm.Apply(i)))
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}
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return Shuffle{
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Shuffled: elgamal.NewCiphertextVector(shuffled),
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Perm: perm,
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Rho: emath.ZqVectorOf(rhoElems...),
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}
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}
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