# Show HN: Source-available post-quantum messenger – crypto core on GitHub

> Source: <https://github.com/VeilusDigital/PhantomChatCrypto>
> Published: 2026-06-24 04:16:36+00:00

The cryptographic core of **Phantom Chat** (Veilus Digital), extracted verbatim
from the iOS app so it can be **read, compiled, and run** by anyone — reviewers,
journalists, security researchers — without taking our word for anything.

Source-available for review.You may read, build, and run this code to verify our claims. You maynotreuse it in another product. See`LICENSE`

.

The rest of the app and the backend remain closed-source; this package is the part where the security actually lives.

| File | What it is |
|---|---|
`Sources/PhantomChatCrypto/Kyber768.swift` |
ML-KEM-768 (FIPS 203) — post-quantum KEM, pure Swift |
`Sources/PhantomChatCrypto/Keccak.swift` |
Keccak-f[1600] + SHA3-256/512 + SHAKE128/256 (FIPS 202) |
`Sources/PhantomChatCrypto/PQXDHHybrid.swift` |
Hybrid combiner: classical X3DH secret + Kyber secret → root key |
`Sources/PhantomChatCrypto/DoubleRatchet.swift` |
Signal-protocol Double Ratchet (per-message keys, forward secrecy) |

These files are **byte-for-byte identical** to the app's `CryptoService.swift`

/
`DoubleRatchet.swift`

(only the `import`

lines differ). The companion document
`phantom-chat-claim-audit.md`

maps each marketing claim to these files.

```
swift test
```

That runs (all must pass):

**FIPS 202 known-answer tests**— SHA3-256/512 and SHAKE128/256 against the published NIST reference values.** NTT correctness**— polynomial multiply checked against a schoolbook negacyclic convolution.** Reduction correctness**— Barrett reduction checked congruent across the entire`Int16`

input range; canonical encoding verified.**ML-KEM-768 round-trips**— KeyGen → Encaps → Decaps agree; tampered ciphertext triggers implicit rejection.** Double Ratchet**— encrypt/decrypt round-trip.** PQXDH hybrid combiner**— deterministic and transcript-bound.** FIPS-203 conformance vs Apple CryptoKit**(`FIPSInteropTests`

, requires macOS 26+): Phantom's Kyber and Apple's vetted`MLKEM768`

exchange shared secrets**both directions**, and for the** same seed**Phantom's public key is** byte-identical**to Apple's. This is the strongest possible evidence that this is genuinely standard ML-KEM-768, not a look-alike.

- This is a
**clean-room Swift implementation** of published standards (FIPS 202, FIPS 203, Signal Double Ratchet/X3DH),**not** libsignal or liboqs. The algorithms are standard; the implementation is ours. - It has
**not** had a paid third-party audit yet — that's on the roadmap. We're publishing it precisely so it can be reviewed. - The interop tests use Apple's CryptoKit as the reference oracle; they need macOS 26 or later to run (older OSes will skip them).
- Found a problem?
`support@veilusdigital.co`

. We'd rather hear it from you.