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https://github.com/saymrwulf/swisspost-evoting-go-poc.git
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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>
29 lines
999 B
C
29 lines
999 B
C
/* Transport security primitives — C ABI exposed by the Rust transportsec crate.
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* Ed25519: 32-byte seed, 32-byte public key, 64-byte signature.
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* X25519: 32-byte private scalar, 32-byte public point, 32-byte shared secret.
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* Return codes: 0 = OK, -1 = null pointer, -2 = bad key, -3 = verification failed.
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*/
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#ifndef TRANSPORTSEC_H
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#define TRANSPORTSEC_H
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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int32_t ts_ed25519_keygen(uint8_t *seed_out, uint8_t *pub_out);
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int32_t ts_ed25519_sign(const uint8_t *seed, const uint8_t *msg, size_t msg_len,
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uint8_t *sig_out);
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int32_t ts_ed25519_verify(const uint8_t *pubkey, const uint8_t *msg,
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size_t msg_len, const uint8_t *sig);
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int32_t ts_x25519_keygen(uint8_t *priv_out, uint8_t *pub_out);
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int32_t ts_x25519_dh(const uint8_t *privkey, const uint8_t *peer_pub,
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uint8_t *shared_out);
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#ifdef __cplusplus
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}
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#endif
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#endif /* TRANSPORTSEC_H */
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