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

Veilus Digital released the cryptographic core of its Phantom Chat messenger as source-available code on GitHub, allowing independent verification of its post-quantum security claims. The package includes implementations of ML-KEM-768, SHA-3, the Signal Double Ratchet, and a hybrid key exchange, all passing interoperability tests against Apple's CryptoKit. The company invites security researchers to review the code, though it has not yet undergone a paid third-party audit.

read2 min views5 publishedJun 24, 2026
Show HN: Source-available post-quantum messenger – crypto core on GitHub
Image: source

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. SeeLICENSE

.

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 entireInt16

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 vettedMLKEM768

exchange shared secretsboth directions, and for the** same seedPhantom'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.

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