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.
62 lines
1.8 KiB
Go
62 lines
1.8 KiB
Go
package protocol
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import (
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"fmt"
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"math/big"
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"github.com/user/evote/pkg/hash"
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emath "github.com/user/evote/pkg/math"
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"github.com/user/evote/pkg/returncodes"
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)
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// ConfirmVote simulates vote confirmation (voter enters BCK).
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func ConfirmVote(event *ElectionEvent, voterIdx int) string {
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cfg := event.Config
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vc := event.VotingCards[voterIdx]
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// Combine LVCC shares from all CCs
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combined := cfg.Group.Identity()
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for _, cc := range event.CCs {
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share := computeLVCCShare(cc, event, vc.VerificationCardID)
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combined = combined.Multiply(share)
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}
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// Hash to get lVCC value
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lVCCVal := returncodes.ComputeLVCCValue(combined, vc.VerificationCardID, cfg.ElectionID)
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// Look up in mapping table
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code, err := event.MappingTable.Lookup(lVCCVal)
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if err != nil {
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return "???"
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}
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fmt.Printf(" Voter %d: vote confirmed (VCC: %s)\n", voterIdx, code)
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return code
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}
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func computeLVCCShare(cc *ControlComponent, event *ElectionEvent, vcID string) emath.GqElement {
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cfg := event.Config
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group := cfg.Group
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zqGroup := emath.ZqGroupFromGqGroup(group)
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// Derive voter-specific confirmation key
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info := fmt.Sprintf("VoterVoteCastReturnCodeGeneration%s%s", cfg.ElectionID, vcID)
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kVal := new(big.Int).SetBytes(hash.RecursiveHash(
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hash.HashableString{Value: info},
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hash.HashableBigInt{Value: cc.ReturnCodeSecret.Value()},
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))
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kVal.Mod(kVal, group.Q())
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k, _ := emath.NewZqElement(kVal, zqGroup)
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// Hash the confirmation key
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ckVal := hash.RecursiveHashToZq(group.Q(),
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hash.HashableString{Value: "ConfirmationKey"},
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hash.HashableString{Value: vcID},
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)
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ckPlusOne := new(big.Int).Add(ckVal, big.NewInt(1))
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// Square to ensure group membership
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ckSquared := new(big.Int).Exp(ckPlusOne, big.NewInt(2), group.P())
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hCK := hash.HashAndSquare(ckSquared, group)
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return hCK.Exponentiate(k)
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}
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