---
> **13.2.0: sealed pubsub groups.** `group => Prefix` on `macula:publish/5`
> and `macula:subscribe/5` seals a group's events to its members, with keys
> the org's distributor (`macula_group_keys`) hands to members that hold the
> org's grant and a live realm membership. An event a subscriber cannot open
> arrives as `macula_event_unopened`, never silently. Like sealed calls it
> waits for `kem_advertise`. See the
> [Pub/Sub guide](docs/guides/pubsub/PUBSUB_GUIDE.md) and
> [the design](https://github.com/macula-io/macula/blob/main/plans/DESIGN_E2E_SEALED_PUBSUB.md).
>
> 13.2.0 is also the **first handshake v5 release**: a connection is
> authenticated once, by proofs bound to its TLS session, instead of, in
> pq_hybrid, by a signature on every control frame. A station that runs it makes it its
> rollback floor. See [CHANGELOG.md](CHANGELOG.md) and
> [the design](https://github.com/macula-io/macula/blob/main/plans/DESIGN_NEIGHBOUR_CHANNEL_BINDING.md).
> **13.1.0: knowing a call was sealed.** A caller can ask for the seal
> report of a call (`report => true` on `macula:call/6` or `call_station/8`)
> or a stream (`macula:stream_report/1`): `sealed` 1 with the id of the KEM
> key the exchange was sealed to, or 0 for a clear one, and the provider it
> was addressed to. It states that sealing ran on that exchange, nothing more.
> See [the design](https://github.com/macula-io/macula/blob/main/plans/DESIGN_E2E_SEAL_REPORT.md).
> **13.0.0: sealed calls and streams.** A caller can seal a call's or a
> stream's payload to the provider's KEM key (ML-KEM-1024, plus P-384 in
> `pq_hybrid`), taken from the provider's signed advertisement, and the
> provider seals what it answers. It is **off by default**: a node names its
> key only once `kem_advertise` is `enabled`, which waits until every station
> runs a release on macula 12.11 or later and every caller runs 13. Routing
> fields, sizes, timing, and a request's UCAN token stay visible to stations.
> Content (D27) transfers are not sealed. See
> [the design](https://github.com/macula-io/macula/blob/main/plans/DESIGN_E2E_PAYLOAD_CONFIDENTIALITY.md), §9.
>
> **Breaking API:** a call or stream to an explicit station
> (`macula:call_station/7,8`, `call_stream_station`) needs `advertisement`,
> `confidential => required` or `confidential => off`, and is otherwise
> refused as `{confidentiality, no_signed_state}`. See
> [CHANGELOG.md](CHANGELOG.md).
> **12.0.0: post-quantum key exchange AND post-quantum signatures.**
> Every QUIC link negotiates
> `SecP384r1MLKEM1024`, then `SecP256r1MLKEM768`, and nothing classical,
> from the [`macula-pqc`](https://crates.io/crates/macula-pqc) crate. Every
> signature is ML-DSA-87 on
> [`macula-mldsa`](https://crates.io/crates/macula-mldsa): node keys, UCAN
> tokens, and the self-signed certificate a listener presents, which a dial
> verifies and nothing classical can replace. A station dial is bound end to
> end: the station's identity key signs a binding over its TLS key, the
> client checks it against the certificate that handshake received, and the
> CONNECT proof covers the same certificate.
>
> ⚠ **Erlang distribution over QUIC is the exception**: those dials run no
> connection handshake yet, so they verify that the peer holds its
> certificate's key and nothing about who it is.
>
> **Breaking on the wire:** a node on 11.5.0 or earlier cannot connect to
> this version, in either direction. See [CHANGELOG.md](CHANGELOG.md).
> **Since 10.5.0**: every supervised primitive pair is complete and
> symmetric, each wrapping its raw SDK primitive as an OTP behaviour with a
> `simple_one_for_one` factory supervisor, mesh-visible protocol facts
> (`sharing.*_v1`, `streaming.*_v1`, `rpc.*_v1`) around its own side of the
> operation, and both a pooled and a **direct-dial** (resolve + one-hop
> dial) mode:
> - **RPC** — `macula_request`/`macula_response`, unary call/reply.
> - **Pub/Sub** — `macula_publisher`/`macula_subscriber`, publish and
> per-publisher-ordered subscribe.
> - **Content sharing** — `macula_feeder`/`macula_download` over
> `macula:share_content/3,4` and `get_content/3,4`: the node that shares
> content keeps and serves it (stations only relay), and a fetcher
> verifies every chunk against the content id it asked for.
> - **Streaming RPC** — `macula_streamer`/`macula_stream_sink`, server /
> client / bidi modes, with an optional `client_stream` receive loop and
> terminal-reply callback, and abort-wired cancel.
> - **Push-initiated content transfer** — `macula_pusher`/`macula_upload`
> push a file at a specific, already-known recipient (rather than sharing
> it for anyone to fetch by its content id), with
> the same chunk/hash/verify integrity guarantees, over `client_stream`.
> - **Overlay (HyParView + Plumtree)** — realm-scoped bounded partial
> views and epidemic broadcast trees, absorbed from the standalone
> `macula-hyparview`/`macula-plumtree` packages. No supervised wrapper yet
> — see the [HyParView](docs/guides/overlay/HYPARVIEW_GUIDE.md) and
> [Plumtree](docs/guides/overlay/PLUMTREE_GUIDE.md) guides.
>
> See [CHANGELOG.md](CHANGELOG.md) for the full version-by-version history.
## What is Macula?
Macula is an **Erlang/OTP client SDK** for building applications on a mesh of
**stations** — realm-agnostic relays that route over QUIC (HTTP/3) and form a
Kademlia DHT. Your service or daemon connects **outbound** to one or more
stations: no open ports, NAT-friendly, no VPN. It provides:
- **RPC (request/response)** — discover a provider in the DHT, then **dial its
serving station directly** (one hop), with the provider's authorization
checked against the realm-signed org directory.
- **Pub/Sub** — topic-based event fan-out across stations, with per-publisher
ordered delivery.
- **Content** — content-addressed sharing and live streaming (MCID).
- **DHT records** — signed, TTL'd records (advertisements, endpoints, more).
- **Sealed calls and streams** — a payload sealed to the provider's KEM key
(off until `kem_advertise` is enabled).
- **Erlang distribution over mesh** — `net_adm:ping` across firewalls, no VPN.
- **TCP bridge** — an unmodified TCP client reaches an unmodified TCP service
across the mesh, one stream per connection, under the procedure's auth
policy (`macula_bridge`).
- **Identity** — ML-DSA-87 node keys (with an RSA-PSS half under `pq_hybrid`), and UCAN tokens they sign.
- **MRI** — typed, hierarchical resource identifiers.
- **Zero-config LAN clustering** — UDP-multicast gossip.
The station (routing, DHT, SWIM, peering) is a separate repo,
[macula-station](https://github.com/macula-io/macula-station); this package is
the client you build against.
---
## Quick Start
Add to `rebar.config`:
```erlang
{deps, [{macula, "~> 13.0"}]}.
```
Or in Elixir `mix.exs`:
```elixir
defp deps do
[{:macula, "~> 13.0"}]
end
```
12.0.0 breaks on the wire: a node on 11.5.0 or earlier cannot connect to
it, in either direction, and there is no classical fallback for either key
exchange or authentication. Upgrade every node together.
```erlang
%% Every node runs one post-quantum crypto profile, pq_pure
%% or pq_hybrid. The application refuses to start without one.
ok = application:set_env(macula, crypto_profile, pq_pure),
application:ensure_all_started(macula),
%% Connect a pool to one or more stations (seed URLs). The pool owns one
%% QUIC link per seed, reconnecting and replaying subscriptions as needed.
{ok, Pool} = macula:connect([<<"quic://boot.macula.io:443">>], #{}),
%% A realm is a 32-byte tag derived from a name; it scopes every call.
%% Keep the name around too — topics are built from it, not the tag.
RealmName = <<"io.example.myapp">>,
Realm = macula_realm:id(RealmName),
%% Topics/procedures are built via macula_topic, never hand-typed — a
%% typo becomes a wrong VALUE your own tests catch, not two strings
%% silently drifting apart. Facts (pub/sub) are past tense; hopes (RPC)
%% are present tense. See docs/guides/shared/TOPIC_NAMING_GUIDE.md.
Topic = macula_topic:app_fact(RealmName, <<"example">>, <<"myapp">>,
<<"sensors">>, <<"temperature_measured">>, 1),
Procedure = macula_topic:app_hope(RealmName, <<"example">>, <<"myapp">>,
<<"math">>, <<"add">>, 1),
%% Subscribe (delivers {macula_event, Ref, Topic, Payload, Meta} to a pid),
{ok, Ref} = macula:subscribe(Pool, Realm, Topic, self()),
%% or subscribe with a callback fun(Topic, Payload, Meta):
{ok, Ref2} = macula:subscribe_callback(
Pool, Realm, Topic,
fun(_Topic, Payload, _Meta) -> io:format("~p~n", [Payload]) end),
%% Publish. Entity IDs go in the PAYLOAD, never in the topic.
ok = macula:publish(Pool, Realm, Topic,
#{sensor => <<"kitchen">>, value => 23.5}),
%% Advertise an RPC procedure (open to any identified caller here),
ok = macula:advertise(Pool, Realm, Procedure,
fun(#{<<"a">> := A, <<"b">> := B}) -> {ok, A + B} end,
#{}),
%% Call it — the SDK resolves the provider and dials its station directly.
{ok, 5} = macula:call(Pool, Realm, Procedure,
#{<<"a">> => 2, <<"b">> => 3}, 5_000).
```
---
## Identity and Crypto (NIF-accelerated)
A node holds one key per purpose in its crypto profile. In `pq_pure` a key
is ML-DSA-87; in `pq_hybrid` an identity key pairs ML-DSA-87 with RSA-PSS and
signs the IETF LAMPS composite `id-MLDSA87-RSA4096-PSS-SHA512`. ML-DSA is
[`macula-mldsa`](https://crates.io/crates/macula-mldsa), verified against
NIST's ACVP vectors, in a Rust NIF with no Erlang fallback, and new keys are
stored as their 32-byte seed. The node_id is SHA-256 over the identity key.
```erlang
{ok, Key} = macula_node_keys:generate(identity, pq_pure),
{ok, NodeId} = macula_node_keys:node_id(Key),
Sig = macula_node_keys:sign(<<"hello">>, Key),
true = macula_node_keys:verify(<<"hello">>, Sig, macula_node_keys:public_key(Key), pq_pure),
ok = macula_node_keys:save("identity.key", Key),
%% BLAKE3 hashing
Hash = macula_blake3_nif:hash(<<"hello">>).
```
UCAN capability tokens (`macula_ucan`) are signed by node keys too, with
the profile's `alg`: `ML-DSA-87` in `pq_pure` and `ML-DSA-87-PS384`, the
LAMPS composite, in `pq_hybrid`. A token names its issuer by `did:key` and
its audience by node_id, and an EdDSA token is refused (see the
[Authorization guide](docs/guides/shared/AUTHORIZATION_GUIDE.md)).
---
## Documentation
| Guide | Description |
|-------|-------------|
| [Connecting](docs/guides/shared/CONNECTING_GUIDE.md) | Pools, seeds, expected identities, reconnection |
| [PubSub Guide](docs/guides/pubsub/PUBSUB_GUIDE.md) | Fan-out + per-publisher delivery ordering |
| [PubSub Protocol](docs/guides/pubsub/PUBSUB_PROTOCOL.md) | Raw `subscribe`/`publish` primitives |
| [Topic Naming](docs/guides/shared/TOPIC_NAMING_GUIDE.md) | Event-type topics, IDs in payloads |
| [RPC Guide](docs/guides/rpc/RPC_GUIDE.md) | Direct-dial request/response |
| [RPC Protocol](docs/guides/rpc/RPC_PROTOCOL.md) | Raw `advertise`/`call` primitives, error codes |
| [Content Guide](docs/guides/content/CONTENT_GUIDE.md) | Content-addressed blobs (MCID), push/upload |
| [Content Protocol](docs/guides/content/CONTENT_PROTOCOL.md) | The content id, the announcement, the content procedure, the fetch and its bounds |
| [Records Guide](docs/guides/shared/RECORDS_GUIDE.md) | Signed, TTL'd facts in the DHT — your own record types |
| [Streaming Guide](docs/guides/streaming/STREAMING_GUIDE.md) | Streaming RPC (server / client / bidi) |
| [Streaming Protocol](docs/guides/streaming/STREAMING_PROTOCOL.md) | Raw `call_stream`/`advertise_stream` primitives |
| [HyParView Guide](docs/guides/overlay/HYPARVIEW_GUIDE.md) | Bounded partial-view realm membership |
| [Plumtree Guide](docs/guides/overlay/PLUMTREE_GUIDE.md) | Epidemic broadcast trees, realm PubSub, OR-Set CRDT |
| [Distribution Over Mesh](docs/guides/DIST_OVER_MESH_GUIDE.md) | Erlang dist through the mesh |
| [Clustering](docs/guides/CLUSTERING_GUIDE.md) | LAN gossip clustering |
| [Authorization](docs/guides/shared/AUTHORIZATION_GUIDE.md) | Node keys, UCAN, provider authorization |
| [MRI Guide](docs/guides/shared/MRI_GUIDE.md) | Resource identifiers |
| [Development](docs/guides/DEVELOPMENT.md) | Building and testing |
| [Glossary](docs/GLOSSARY.md) | Terminology |
The station server lives in
[macula-station](https://github.com/macula-io/macula-station).
---
## Related Projects
| Project | Description |
|---------|-------------|
| [macula-station](https://github.com/macula-io/macula-station) | The station: DHT, SWIM, routing, peering |
| [macula-realm](https://github.com/macula-io/macula-realm) | Managed-realm identity + certificate authority |
| [macula-mri-khepri](https://github.com/macula-io/macula-mri-khepri) | Distributed MRI persistence (Khepri/Raft) |
| [macula-ecosystem](https://github.com/macula-io/macula-ecosystem) | Documentation hub |
---
## License
Apache 2.0 — see [LICENSE](LICENSE).
---
