Module echo_broadcast 

Available on crate feature echo-broadcast only.

Reliable broadcast for any protocol via echo messages

Broadcast message is a message meant to be received by all participants of the protocol.

We say that message is reliably broadcasted if, upon reception, it is guaranteed that all honest participants of the protocol has received the same message.

One way to achieve the reliable broadcast is by adding an echo round: when we receive messages in a reliable broadcast round, we hash all messages, and we send the hash to all other participants. If party receives a the same hash from everyone else, we can be assured that messages in the round were reliably broadcasted.

This module provides a mechanism that automatically add an echo round per each round of the protocol that requires a reliable broadcast.

Example

// protocol to be executed that **requires** reliable broadcast
async fn keygen<M>(mpc: M, i: u16, n: u16) -> Result<KeyShare>
where
    M: round_based::Mpc<Msg = KeygenMsg>
{
    // ...
}
// The full message type, which corresponds to keygen msg + echo broadcast msg
type Msg = round_based::echo_broadcast::Msg<sha2::Sha256, KeygenMsg>;
// establishes network connection(s) to other parties, but
// **does not** support reliable broadcast
async fn connect() ->
    impl futures::Stream<Item = Result<round_based::Incoming<Msg>>>
        + futures::Sink<round_based::Outgoing<Msg>, Error = Error>
        + Unpin
{
    // ...
}
let delivery = connect().await;

// constructs an MPC engine as usual
let mpc = round_based::mpc::connected(delivery);
// wraps an engine to add reliable broadcast support
let mpc = round_based::echo_broadcast::wrap(mpc, i, n);

// execute the protocol
let keyshare = keygen(mpc, i, n).await?;

Structs

EchoError

An error in echo-broadcast sub-protocol

Round

Round registration witness returned by WithEchoBroadcast::add_round()

WithEchoBroadcast

Mpc engine with echo-broadcast capabilities

Enums

CompleteRoundError

An error returned in round completion

Error

An error originated either from main protocol or echo-broadcast sub-protocol

Msg

Message of the protocol with echo broadcast round(s)

Functions

wrap

Wraps an Mpc engine and provides echo broadcast capabilities