mirror of
https://github.com/saymrwulf/swisspost-evoting-go-poc.git
synced 2026-07-21 19:19:01 +00:00
saymrwulf
ec4be74e17
Correctness/security review of the whole PoC, with fixes and regression tests.
Cryptographic soundness:
- mixnet: enforce the multi-exponentiation c_{B_m}=commit(0;0) check that was
stubbed out with an empty if — without it a malicious mixer can prove a
non-permutation shuffle.
- zkp: derive all four Fiat-Shamir challenges via RecursiveHashToZq instead of
a biased `hash mod q` (which also capped the challenge space at 256 bits for
production-sized groups).
Verification honesty:
- protocol: VerifyTally now actually calls zkp.VerifySchnorrProof and returns
the true aggregate result instead of an unconditional true.
- protocol: persist the padded mix input (event.MixInput) so the verifier checks
shuffle 0 against the same padding the tally used (fixes false INVALID for N<2).
Other correctness:
- kdf: length-prefix BuildKDFInfo parts so the info encoding is injective.
- math: GqElementFromSquareRoot accepts the valid root q (off-by-one that could
panic in HashAndSquare); RandomGqElement samples the full canonical range.
- cmd: validate demo --voters/--options instead of panicking on degenerate values.
- protocol: use crypto/rand in the demo driver (drop the last math/rand import).
Transport security (new): pkg/transportsec exposes Ed25519 signatures and X25519
ECDH — implemented in Rust (rust/transportsec: ed25519-dalek, x25519-dalek),
linked into Go via cgo. No RSA. Cross-language conformance test proves the Rust
Ed25519 signatures interoperate with Go's crypto/ed25519. Makefile builds the
Rust static lib before the Go binary.
Tests: added unit/round-trip/tamper coverage for math, hash, elgamal, zkp,
mixnet, kdf, returncodes, protocol (end-to-end), and the Rust FFI bridge.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
66 lines
1.9 KiB
Go
66 lines
1.9 KiB
Go
package protocol
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import (
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"math/big"
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"testing"
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emath "github.com/user/evote/pkg/math"
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)
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const (
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testP = "179688417486862032111147025351064878713905624387098436271724698527496946737299"
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testQ = "89844208743431016055573512675532439356952812193549218135862349263748473368649"
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testG = "4"
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)
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func testConfig(t *testing.T, numVoters, numOptions int) *Config {
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t.Helper()
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p, _ := new(big.Int).SetString(testP, 10)
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q, _ := new(big.Int).SetString(testQ, 10)
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g, _ := new(big.Int).SetString(testG, 10)
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group, err := emath.NewGqGroup(p, q, g)
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if err != nil {
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t.Fatalf("test group: %v", err)
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}
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return &Config{
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Group: group,
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NumCCs: 4,
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NumOptions: numOptions,
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NumVoters: numVoters,
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ElectionID: "unit-test",
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SecurityLvl: 128,
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}
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}
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// TestEndToEndTallyAndVerify runs the full ceremony deterministically (fixed
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// group, fixed votes) and asserts both the decoded result and that the honest
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// verifier returns true — this is the regression guard for the F2/F7 fixes
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// (VerifyTally must now return the real outcome, and small-N padding must match).
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func TestEndToEndTallyAndVerify(t *testing.T) {
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for _, tc := range []struct {
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voters int
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options int
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votes []int // one selection per voter
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want map[int]int
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}{
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{voters: 3, options: 3, votes: []int{0, 1, 1}, want: map[int]int{0: 1, 1: 2}},
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{voters: 1, options: 2, votes: []int{0}, want: map[int]int{0: 1}}, // exercises N<2 padding
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{voters: 4, options: 2, votes: []int{0, 0, 1, 1}, want: map[int]int{0: 2, 1: 2}},
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} {
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cfg := testConfig(t, tc.voters, tc.options)
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event := Setup(cfg)
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for v := 0; v < tc.voters; v++ {
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CastVote(event, v, []int{tc.votes[v]})
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}
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Tally(event)
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for opt, want := range tc.want {
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if event.FinalResult[opt] != want {
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t.Errorf("voters=%d: option %d got %d, want %d", tc.voters, opt, event.FinalResult[opt], want)
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}
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}
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if !VerifyTally(event) {
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t.Errorf("voters=%d: honest ceremony failed verification", tc.voters)
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}
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}
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}
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