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ARCHITECTURE.md

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Architecture

Layers

The caring crate is loosely split into the following different "modules" or traits, with lower levels being more concrete and higher levels more abstract.

              VM Engine
  Protocols      |
     \__________InteractiveShared
                  /           \
               Communicate   Shared
                |              |
               Network       Schemes (shamir, spdz, etc.) 
                |
               Connection

At the lowest level we have the raw Connection<R,W> implementation, which can be anything that implements tokio::AsyncRead/tokio::AsyncWrite, such as the TcpConnection or (in-memory) DuplexConnection. This is abstracted away to a SendBytes/RecvBytes and Channel/SplitChannel traits, which allows for any kind of abstract channel for sending and receiving bytes, such as the multiplexing module caring::net::mux.

A group of connections then form a Network which allows for more broad communication by broadcast, uni(que)cast or tuning to a specific channel. This enables the traits Broadcast, Unicast, Tuneable forming Communicate. The reasoning behind this allowing protocols to specify if they only need to broadcast/unicast, and such can specialize in different kinds depending on the scenario. Furthermore, it allows different schemes of verifiable broadcasts to be swapped in place.

Networking

Note A lot of functions are defined in terms of items that belong to specific party, thus using a Vec or slice. The order of these matter, since it will be implied that index i belongs to player/party i.

Schemes

Interactive vs Non-interactive Schemes

There are two main traits defining a secret sharing scheme, the first one is the Shared which is for schemes such as shamir and feldman where the protocols for sharing, reconstruction, etc., does not need interactive communication from the other parties, but can simply be made locally.

The InteractiveShared trait however does define asynchronous functions for performing sharing and reconstruction with the aid of the Communication trait. All non-interactive Shared schemes can all function as interactive due to a blanket implementation.

Shares

The share is simply a struct containing (usually) the finite field of the secret shared data. In the case of Shamir Secret Sharing (and derivatives) the (public) x field is left out, as it is implied by the holder, except for the cases of sharing and reconstruction, where it is implied by the index. This is both to minimize the memory footprint of shares and to more strictly enforce checks on the x, as it could be cheated with, and we would then require context based parsing for all shares, which would be difficult.

Protocols

Testing Framework