The running cryptography now narrates itself. Each headline operation emits a
trace.Event carrying its LaTeX notation plus the actual runtime values, the
instant it executes:
- Ed25519 signature on every inter-party message (envelope.Seal)
- X25519 ECDH key agreement for confidential card delivery (NewSecureChannel)
- ElGamal ballot encryption E1 = (g^r, pk^r·m) with the real r (castBallot)
- Fiat-Shamir challenge e = H(...) mod q (Schnorr proof)
- Bayer-Groth verifiable shuffle C' = {ReEnc_pk(C_π(i))} with N (mix-net)
Ceremony phases set trace phase/party context so events are attributed to the
acting stakeholder and phase. Instrumentation is behind the enabled-check, so
normal runs pay nothing.
Test: a full traced ceremony captures 184 live events across all five headline
kinds, each with non-empty LaTeX and live values, correctly phase/party-tagged.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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>
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.
