Custom WebSocket Client
Overview
The CloudWebSocketClient class is a protocol-aware WebSocket client designed specifically for MPC (Multi-Party Computation) operations. It serves as a thin wrapper around the SilentShardWebSocketClient which implements IWebSocketClient from @silencelaboratories/silent-shard-sdk.
1. CloudWebSocketClient
- Role: Protocol-aware MPC client
- Responsibility:
- MPC-specific URL construction
- Operation routing (keygen/sign/refresh)
- Customization Use Cases:
- Add authentication headers
2. SilentShardWebSocketClient implements IWebSocketClient
- Role: Low-level WebSocket implementation
- Responsibility:
- Raw WebSocket connection management
- Message queueing and asynchronous I/O
- Binary/text data transmission
- Customization Use Cases:
- Replace WebSocket library (e.g., Socket.IO, different WebSocket impl)
- Modify low-level message queueing logic
Example adding authentication headers to WebSocket connection
import { CloudWebSocketClient } from '@silencelaboratories/silent-shard-sdk';
import { createEcdsaDuoSession } from '@silencelaboratories/silent-shard-sdk/ecdsa';
import type { WebSocketAction } from '@/silent-shard-sdk/src/network/WebSocketAction';
class CustomCloudClient extends CloudWebSocketClient {
connect(opt: WebSocketAction): Promise<void> {
// You can read your client ID and access token from environment variables or a secure store.
const token = 'client-access-token-here';
const headers = {
'client-id': 'your-client-id-here',
'access-token': token,
};
return super.connect(opt, { headers });
}
}
// Then you can use the CustomCloudClient in Session objects
const customClient = new CustomCloudClient('CLOUD_NODE_URL', true); // true for WSS, false for WS
createEcdsaDuoSession({
client: customClient,
cloudVerifyingKey: '',
});
Overview
The CloudClient class is a protocol-aware WebSocket client designed specifically for MPC (Multi-Party Computation) operations. It serves as a thin wrapper around the WebSocketClient which implements WebSocketClientInterface from silent-shard-sdk.
1. CloudClient
- Role: Protocol-aware MPC client
- Responsibility:
- MPC-specific URL construction
- Operation routing (keygen/sign/refresh)
- Customization Use Cases:
- Add authentication headers
2. WebSocketClient implements WebSocketClientInterface
- Role: Low-level WebSocket implementation
- Responsibility:
- Raw WebSocket connection management
- Message queueing and asynchronous I/O
- Binary/text data transmission
- Customization Use Cases:
- Replace WebSocket library (e.g., Socket.IO, different WebSocket impl)
- Modify low-level message queueing logic
Example adding authentication headers to WebSocket connection
import 'package:silent_shard_sdk/silent_shard_sdk.dart' as sdk;
// To add custom header with each connection
class CloudSocketClient extends sdk.CloudClient {
final String userToken;
CloudSocketClient(
{required super.baseUri,
required this.userToken,
required super.isSecure,
super.webSocketClient})
: super();
Future<void> connect(String uri, [String protocol = 'duo-instance']) {
return webSocketClient.connect(uri: uri, protocol: protocol, headers: {
'Authorization': 'Bearer $userToken',
});
}
}
Future<void> setup() async {
final customCloudClient = CloudSocketClient(
baseUri: 'wss://cloud.silent-shard.com',
isSecure: true,
userToken: 'your-token',
);
final session = await sdk.createDuoEcdsaSession(
cloudClient: customCloudClient,
cloudVerifyingKeyHex: 'SERVER_PUBLIC_KEY_HEX',
storageClient: sdk.SimpleStorageClient(),
);
final keyshare = await session.keygen();
print('Keyshare: $keyshare');
}
Overview
Protocol traffic between your app and the cloud peer flows through a NetworkClient — a small transport contract the SDK drives to run each MPC step. The SDK ships a WebSocket implementation, DuoNetworkClient, and uses it automatically when you pass a WebsocketConfig to duoInitiator. You only need this guide if you want to customize that transport.
The NetworkClient contract is a fixed rhythm the session repeats for every protocol step:
| Method | Responsibility |
|---|---|
connect(action, params) | Open a channel for one step. action carries the routing (which operation, which algorithm); params is optional detail such as a keyId. |
send(bytes) / send(text) | Send one framed message to the peer. |
read() | Suspend until the next message arrives, and return its bytes. |
disconnect() | Close the channel. The client stays reusable for the next connect. |
DuoNetworkClient implements this contract over Ktor WebSockets. On connect it:
- opens a session at
wss://<host>/v3/{algorithm}/{action}— for example/v3/ecdsa/keygen; - negotiates the
duo-instanceWebSocket subprotocol; - sends
WebsocketConfig.authenticationTokenas the first message, if you set one.
The underlying HTTP engine is created on connect and released on disconnect, so an idle client holds no transport resources.
Three ways to provide a transport
duoInitiator has three overloads, from zero-config to full control. Pick the one that matches how much of the transport you need to own.
| # | Approach | When to use |
|---|---|---|
| 1 | WebsocketConfig | The default. The SDK builds and owns the WebSocket client. |
| 2 | Subclass DuoNetworkClient | Keep the WebSocket transport, but hook connect / send / read — logging, headers, retry, or route rewriting. |
| 3 | Custom NetworkClient + DuoNetworkActionProvider | Route protocol traffic over a different transport entirely. |
1. Default WebSocket — pass a WebsocketConfig
Give the factory a WebsocketConfig and the SDK builds and owns the default DuoNetworkClient. There is nothing to implement — this is the standard path used in the session setup.
// The default transport. Pass a WebsocketConfig and the SDK builds and owns the
// default DuoNetworkClient (a Ktor WebSocket client) for you — nothing to implement.
val websocketConfig = WebsocketConfig(url = "wss://your-server.example.com")
val duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner = messageSigner,
cloudVerifyingKey = cloudPublicKey,
websocketConfig = websocketConfig,
storageClient = storageClient,
)
2. Customize the WebSocket — subclass DuoNetworkClient
Subclass DuoNetworkClient and override connect (or send / read) to add logging, inject headers, add retry/back-off, or rewrite a route — while reusing the default framing, /v3/{algorithm}/{action} routing, subprotocol negotiation, and engine lifecycle. Pass your subclass to the duoInitiator overload that accepts a DuoNetworkClient.
Import DuoNetworkClient and the DuoNetworkAction types from com.silencelaboratories.silentshard.duo.initiator.network.
import com.silencelaboratories.silentshard.duo.initiator.network.DuoNetworkAction
import com.silencelaboratories.silentshard.duo.initiator.network.DuoNetworkClient
import com.silencelaboratories.silentshard.network.websocket.WebsocketConfig
// Subclass the default client to hook connect / send / read while reusing its framing
// and /v3/{algorithm}/{action} routing. Here we rewrite the keygen route as an example
// and delegate every other action unchanged; you could just as easily log, add headers,
// or wrap the call in retry/back-off before calling super.
class CustomNetworkClient(websocketConfig: WebsocketConfig) : DuoNetworkClient(websocketConfig) {
override suspend fun connect(action: DuoNetworkAction, params: String?) {
val routed = when (action) {
is DuoNetworkAction.ECDSA.Keygen ->
DuoNetworkAction.ECDSA.Keygen(path = "custom-path-for-keygen")
else -> action
}
super.connect(routed, params)
}
}
// Pass your subclass to the DuoNetworkClient overload of duoInitiator.
val duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner = messageSigner,
cloudVerifyingKey = cloudPublicKey,
networkClient = CustomNetworkClient(websocketConfig),
storageClient = storageClient,
)
3. Bring your own transport — implement NetworkClient
The most control: carry protocol traffic over any channel you like. Because the transport only has to move framed bytes between the two parties, this can be a shared app socket, a native bridge, or an already-open host connection — or a peer-to-peer link such as Bluetooth Low Energy (BLE), letting two nearby devices run the protocol directly with no cloud relay (you would map connect / send / read / disconnect onto GATT characteristic writes and notifications).
A custom transport has two halves, and you supply both to the duoInitiator overload that accepts a NetworkClient + DuoNetworkActionProvider.
a. The transport — implement NetworkClient
How bytes move. The SDK drives your client with connect → send/read → disconnect for each step; the action it hands connect is the step your routing selected.
import com.silencelaboratories.silentshard.network.NetworkAction
import com.silencelaboratories.silentshard.network.NetworkClient
// How bytes move. The SDK drives your client with the same rhythm for every step:
// connect → send/read → disconnect. `action` is the concrete step your routing selected.
class CustomTransport : NetworkClient {
override suspend fun connect(action: NetworkAction, params: String?) {
// `action` is the step the provider chose; `params` may carry a keyId.
// Open a channel for it over your transport (WebSocket, app socket, BLE, …).
}
override suspend fun send(bytes: ByteArray) { /* send framed bytes to the peer */ }
override suspend fun send(text: String) { /* send framed text to the peer */ }
override suspend fun read(): ByteArray = TODO("suspend until the next peer message, then return its bytes")
override suspend fun disconnect() { /* close the channel; stay reusable for the next connect */ }
}
b. The routing — implement DuoNetworkActionProvider
How each step is addressed. It exposes one NetworkAction per operation (keygen, reconcile, refresh, sign, import), and the action it supplies is exactly what your client's connect receives. Take DuoNetworkActionProvider.Default.ECDSA / .EdDSA for the standard /v3/{algorithm}/{action} routing, or implement it yourself — every DuoNetworkAction lets you override path / action / protocol / algorithm.
import com.silencelaboratories.silentshard.duo.initiator.network.DuoNetworkAction
import com.silencelaboratories.silentshard.duo.initiator.network.DuoNetworkActionProvider
// How each step is addressed. Every DuoNetworkAction constructor takes
// path / action / protocol / algorithm — override whichever fields you want: pass one,
// spell them all out, or take the defaults, per step.
class CustomActions : DuoNetworkActionProvider {
// Override a single field (here, the route's `path`).
override val keygen = DuoNetworkAction.ECDSA.Keygen(path = "my-keygen-route")
// Spell out every field explicitly.
override val reconcile = DuoNetworkAction.ECDSA.Reconcile(
path = "duo", action = "reconcile", protocol = "duo-instance", algorithm = "ecdsa",
)
// Override the WebSocket subprotocol negotiated on connect.
override val refresh = DuoNetworkAction.ECDSA.KeyRefresh(protocol = "my-duo-instance")
// Override the `action` segment of the /v3/{algorithm}/{action} route.
override val sign = DuoNetworkAction.ECDSA.Signature(action = "signature")
// …or just take the stock routing.
override val import = DuoNetworkAction.ECDSA.Import()
}
// Note: `algorithm` + `action` form the /v3/{algorithm}/{action} route and `protocol`
// is the subprotocol header, so change those only to match your own server; `path`
// only feeds the HTTP POST URL, which duo flows don't use.
c. Wire the two halves into duoInitiator
// Pass both halves — your transport and your routing — to the custom-transport
// overload of duoInitiator.
val duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner = messageSigner,
cloudVerifyingKey = cloudPublicKey,
storageClient = storageClient,
networkClient = CustomTransport(),
actionProvider = CustomActions(), // or DuoNetworkActionProvider.Default.ECDSA
)
Most protocol steps run over the open WebSocket; a few request-response steps run over HTTP POST (sendPostRequest). Duo never needs the POST path — it is only exercised by trio pre-signatures — so a custom duo transport can leave it out.
Overview
Protocol traffic between your app and the cloud peer flows through a NetworkClient — a small transport contract the SDK drives to run each MPC step. The SDK ships a WebSocket implementation, DuoNetworkClient, and uses it automatically when you pass a WebsocketConfig to duoInitiator. You only need this guide if you want to customize that transport.
The NetworkClient contract is a fixed rhythm the session repeats for every protocol step (every method is async throws):
| Method | Responsibility |
|---|---|
connect(action:params:) | Open a channel for one step. action carries the routing (which operation, which algorithm); params is optional detail such as a keyId. |
send(bytes:) / send(text:) | Send one framed message to the peer. |
read() | Suspend until the next message arrives, and return its Data. |
disconnect() | Close the channel. The client stays reusable for the next connect. |
DuoNetworkClient implements this contract over URLSessionWebSocketTask. On connect it:
- opens a task at
wss://<host>/v3/{algorithm}/{action}— for example/v3/ecdsa/keygen; - negotiates the
duo-instanceWebSocket subprotocol; - sends
WebsocketConfig.authenticationTokenas the first message, if you set one.
The underlying URLSession is created on connect and released on disconnect, so an idle client holds no transport resources.
Three ways to provide a transport
duoInitiator has three overloads, from zero-config to full control. Pick the one that matches how much of the transport you need to own.
| # | Approach | When to use |
|---|---|---|
| 1 | WebsocketConfig | The default. The SDK builds and owns the WebSocket client. |
| 2 | Subclass DuoNetworkClient | Keep the WebSocket transport, but hook connect / send / read — logging, headers, retry, or route rewriting. |
| 3 | Custom NetworkClient + DuoNetworkActionProvider | Route protocol traffic over a different transport entirely. |
1. Default WebSocket — pass a WebsocketConfig
Give the factory a WebsocketConfig and the SDK builds and owns the default DuoNetworkClient. There is nothing to implement — this is the standard path used in the session setup.
// The default transport. Pass a WebsocketConfig and the SDK builds and owns the
// default DuoNetworkClient (a URLSession WebSocket client) for you — nothing to implement.
let websocketConfig = WebsocketConfig(url: "wss://your-server.example.com")
let duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner: messageSigner,
cloudVerifyingKey: cloudPublicKey,
websocketConfig: websocketConfig,
storageClient: storageClient
)
2. Customize the WebSocket — subclass DuoNetworkClient
Subclass DuoNetworkClient and override connect (or send / read) to add logging, inject headers, add retry/back-off, or rewrite a route — while reusing the default framing, /v3/{algorithm}/{action} routing, subprotocol negotiation, and session lifecycle. Pass your subclass to the duoInitiator overload that accepts a DuoNetworkClient.
DuoNetworkClient and the DuoNetworkAction types are exported from the duo module (import duo).
import duo
// Subclass the default client to hook connect / send / read while reusing its framing
// and /v3/{algorithm}/{action} routing. Here we rewrite the keygen route as an example
// and delegate every other action unchanged; you could just as easily log, add headers,
// or wrap the call in retry/back-off before calling super.
class CustomNetworkClient: DuoNetworkClient {
override func connect(websocketAction: DuoNetworkAction, params: String?) async throws {
let routed: DuoNetworkAction
switch websocketAction {
case is DuoAction.ECDSA.Keygen:
routed = DuoAction.ECDSA.Keygen(path: "custom-path-for-keygen")
default:
routed = websocketAction
}
try await super.connect(websocketAction: routed, params: params)
}
}
// Pass your subclass to the DuoNetworkClient overload of duoInitiator.
let duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner: messageSigner,
cloudVerifyingKey: cloudPublicKey,
networkClient: CustomNetworkClient(websocketConfig: websocketConfig),
storageClient: storageClient
)
3. Bring your own transport — implement NetworkClient
The most control: carry protocol traffic over any channel you like. Because the transport only has to move framed bytes between the two parties, this can be a shared app socket, a native bridge, or an already-open host connection — or a peer-to-peer link such as Bluetooth Low Energy (BLE), letting two nearby devices run the protocol directly with no cloud relay (you would map connect / send / read / disconnect onto GATT characteristic writes and notifications).
A custom transport has two halves, and you supply both to the duoInitiator overload that accepts a NetworkClient + DuoNetworkActionProvider.
a. The transport — implement NetworkClient
How bytes move. The SDK drives your client with connect → send/read → disconnect for each step; the action it hands connect is the step your routing selected.
import duo
// How bytes move. The SDK drives your client with the same rhythm for every step:
// connect → send/read → disconnect. `action` is the concrete step your routing selected.
class CustomTransport: NetworkClient {
func connect(action: NetworkAction, params: String?) async throws {
// `action` is the step the provider chose; `params` may carry a keyId.
// Open a channel for it over your transport (WebSocket, app socket, BLE, …).
}
func send(bytes: Data) async throws { /* send framed bytes to the peer */ }
func send(text: String) async throws { /* send framed text to the peer */ }
func read() async throws -> Data { Data() /* suspend until the next peer message, then return its bytes */ }
func disconnect() async throws { /* close the channel; stay reusable for the next connect */ }
// sendPostRequest has a default that throws .postRequestUnsupported; duo never needs it.
}
b. The routing — implement DuoNetworkActionProvider
How each step is addressed. It exposes one NetworkAction per operation (keygen, reconcile, refresh, sign, import), and the action it supplies is exactly what your client's connect receives. Take the built-in .ecdsa / .eddsa provider for the standard /v3/{algorithm}/{action} routing, or implement it yourself — every DuoNetworkAction lets you override path / action / protocol / algorithm.
import duo
// How each step is addressed. Every DuoAction.ECDSA.* initializer takes
// path / action / protocol / algorithm — override whichever fields you want: pass one,
// spell them all out, or take the defaults, per step.
struct CustomActions: DuoNetworkActionProvider {
// Override a single field (here, the route's `path`).
let keygen: NetworkAction = DuoAction.ECDSA.Keygen(path: "my-keygen-route")
// Spell out every field explicitly.
let reconcile: NetworkAction = DuoAction.ECDSA.Reconcile(
path: "duo", action: "reconcile", protocol: "duo-instance", algorithm: "ecdsa"
)
// Override the WebSocket subprotocol negotiated on connect.
let refresh: NetworkAction = DuoAction.ECDSA.KeyRefresh(protocol: "my-duo-instance")
// Override the `action` segment of the /v3/{algorithm}/{action} route.
let sign: NetworkAction = DuoAction.ECDSA.Signature(action: "signature")
// …or just take the stock routing.
let `import`: NetworkAction = DuoAction.ECDSA.Import()
}
// Note: `algorithm` + `action` form the /v3/{algorithm}/{action} route and `protocol`
// is the subprotocol header, so change those only to match your own server; `path`
// only feeds the HTTP POST URL, which duo flows don't use.
c. Wire the two halves into duoInitiator
// Pass both halves — your transport and your routing — to the custom-transport
// overload of duoInitiator.
let duoSession = SilentShard.ECDSA.duoInitiator(
messageSigner: messageSigner,
cloudVerifyingKey: cloudPublicKey,
storageClient: storageClient,
networkClient: CustomTransport(),
actionProvider: CustomActions() // or .ecdsa
)
Most protocol steps run over the open WebSocket; a few request-response steps run over HTTP POST (sendPostRequest). Duo never needs the POST path — it is only exercised by trio pre-signatures — so a custom duo transport can leave it out.