Knowledge base Under the hood

Protocol and events

What Nymchat actually puts on the wire, for anyone building against it, auditing it, or reading events from another Nostr client.

Event kinds

Kind	Used for	Notes
`0`	Profile metadata	Standard Nostr profile: name, picture, banner, about, `lud16`.
`5`	Deletion requests	NIP-09.
`7`	Reactions	NIP-25, with a `['k', originalKind]` tag so a reaction is filed against the right channel type.
`13`	Seal	The middle layer of a NIP-17 message.
`14`	Private message rumor	Unsigned, and never published on its own. A thread reply carries a `['nymthread', rootId]` tag inside the encrypted rumor, referencing the root's shared message id.
`1059`	Gift wrap	NIP-59. What actually reaches a relay for private messages and group chats.
`1984`	Reporting	NIP-56.
`9734` / `9735`	Zap request and zap receipt	NIP-57.
`10030`	Custom emoji pack lists	NIP-30.
`20000`	Geohash channel message	Ephemeral, tagged `['g', geohash]`. A thread reply adds a NIP-10 marked `['e', rootId, '', 'root']` tag.
`23333`	Named channel message	Ephemeral, tagged `['d', channel]`. A thread reply adds a NIP-10 marked `['e', rootId, '', 'root']` tag.
`24420` / `24421`	Public typing indicators and read receipts	Nymchat-specific, for public channels.
`25051` / `25052`	Peer-to-peer signaling and file-transfer status	Nymchat-specific.
`30030`	Custom emoji sets	NIP-30.
`30078`	Application data	NIP-78. Polls, encrypted settings sync, and post-quantum key announcements (tagged `nym-pq`, carrying an ML-KEM-768 public key with a NIP-40 expiration).
`69420`	Private read receipts and delivery status	Nymchat-specific, carried as a rumor inside a gift wrap. A separate kind from `14` deliberately, so other NIP-17 clients do not render blank direct messages for every receipt.

NIPs Nymchat implements

NIP	What it gives Nymchat
NIP-07	Login with a browser extension.
NIP-09	Deletion requests.
NIP-10	Marked reply tags — how a channel thread reply points at its root message.
NIP-13	Proof of work. Outgoing messages are mined to at least 16 bits.
NIP-17	Private direct messages, and the basis for group chats.
NIP-25	Reactions.
NIP-30	Custom emoji.
NIP-40	Expiration timestamps — disappearing messages.
NIP-44	Versioned encryption, used for seals, wraps and settings sync.
NIP-46	Remote signing — `bunker://`.
NIP-56	Reporting.
NIP-57	Lightning zaps.
NIP-59	Gift wraps.
NIP-78	Arbitrary application data.
NIP-98	HTTP auth, for the hosted endpoints.

Cryptography

Where	What
Identity and signatures	secp256k1 with Schnorr signatures (BIP-340), as Nostr specifies.
Private messages and group chats	NIP-44 v2: ECDH on secp256k1, HKDF-SHA256, ChaCha20 with HMAC-SHA256, and padding so ciphertext length does not give the message length away.
Private messages and group chats, between Nymchat users	The same NIP-44 v2 payload, unmodified, sealed a second time inside ChaCha20-Poly1305 keyed from an ML-KEM-768 (FIPS 203) encapsulation through HKDF-SHA256. The encapsulation ciphertext and both identity keys are bound in as associated data, and the result carries a `pq2.` prefix so a reader picks the path by inspecting the payload. Both layers must be broken to recover a message. See quantum-resistant encryption.
Bluetooth mesh sessions	Noise XX — X25519, ChaCha20-Poly1305 (IETF), Ed25519 for announce signatures, SHA-256 and HMAC underneath.
Identity at rest	AES-GCM-256. The key comes from PBKDF2-SHA256 at 310,000 iterations for a password or PIN, or from a WebAuthn PRF output through HKDF-SHA256 for a passkey or biometric.
Calls and file transfers	WebRTC's own DTLS-SRTP, negotiated over NIP-17-wrapped signaling.
Randomness	The platform CSPRNG throughout — keys, nonces, and the gift-wrap timestamp jitter.

Metadata protection

Two details in the gift-wrap path are worth calling out, because they are what separate NIP-59 from "encrypted, but obviously from you to them":

Every wrap is signed by a one-time key generated for that message alone, so no two wraps share a sender.
Every wrap's created_at is randomly backdated by up to two hours using the CSPRNG, so send and receive times cannot be lined up.

Group chats add rotating ephemeral recipient keys on top of that — see How group encryption works.

Reading the source

The crypto primitives are in js/nym-crypto.js and js/modules/key-vault.js in the web app, and under android-ios-app/lib/core/crypto/ and lib/services/mesh/noise/ in the Flutter app. The repository is AGPL-3.0 and complete — there is no closed component to take on trust.