swisspost-evoting-go-poc/pkg/math/testgroup_test.go

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Due-diligence hardening + Rust transport-security layer 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>
2026-07-06 12:42:34 +00:00
package math
import (
"math/big"
"testing"
)
// A fixed 256-bit safe prime group (p = 2q+1, both prime, g=4 a generator of
// G_q) used across math tests so they are fast and deterministic.
const (
testP = "179688417486862032111147025351064878713905624387098436271724698527496946737299"
testQ = "89844208743431016055573512675532439356952812193549218135862349263748473368649"
testG = "4"
)
func testGqGroup(t *testing.T) *GqGroup {
t.Helper()
p, _ := new(big.Int).SetString(testP, 10)
q, _ := new(big.Int).SetString(testQ, 10)
g, _ := new(big.Int).SetString(testG, 10)
group, err := NewGqGroup(p, q, g)
if err != nil {
t.Fatalf("test group construction failed: %v", err)
}
return group
}