Open TSS

This project is a Rust implementation of multi-party {t,n}-threshold signature scheme(TSS).

The current version of this library supports ECDSA, other algorithms such as EdDSA, BLS, etc. will be integrated soon. Please look forward to it!

Multi-Party ECDSA

ECDSA is widely used in crypto-currencies, such as BTC, Ethereum (secp256k1 curve), etc.

The multi-party ECDSA protocol in this library is implemented based on class group. It currently includes two protocols:

• Key Generation for creating secret shares.
• Signing for using the secret shares to generate a signature. This can be divided into two phases, Offline and Online:
  • The Offline phase is independent of the message to be signed and can be calculated in advance.
  • Simply passing the message (and the output of Offline) to the Online phase, and you can get the signature very quickly.

The ECDSA in this library includes schemes described in [DMZ+21](published in Asiacrypt 2021).

Protocol	Introduction
[DMZ+21]	- This paper proposes efficient multi-party threshold ECDSA protocols from CL encryptions based on class groups. - This protocol avoids the low order assumption, which is a strong and non-standard assumption, and reduces the communication cost in keygen.

Usage

Let's take KeyGen for example, only need three steps. Assuming $(t,n) = (1,3)$, party ids are 1, 2, 3.

Step 1: New a Phase object.

let partyid = "1".to_string();
let params = Parameters {
    threshold: 1,
    share_count: 3,
};
let party_ids = vec!["1".to_string(), "2".to_string(), "3".to_string()];
let mut keygen = KeyGenPhase::new(partyid, params, &Some(party_ids)).unwrap();

Step 2: Start by calling process_begin, which returns the message to be sent in the next round.

let sending_msg: SendingMessages = keygen.process_begin().unwrap();

According to the SendingMessages type(Broadcast, P2P, etc.) and content, we can package the index(from, self partyid) with the message(msg) to the other participant(s).

match sending_msg {
    SendingMessages::BroadcastMessage(msg) => {
        // broadcast the msg to all(including self).
    }
    SendingMessages::P2pMessage(msg) => {
        // send according to the k,v in the msg. k is the index which v will to be sent to.
    }
    SendingMessages::SubsetMessage(msg) => {
        // send according to the k in the party_ids or subset(used in sign phase). k is the index which msg will to be sent to.
    }
    _ => {}
}

Step 3: Handling messages by msg_handler.

When a message has been received, got the recv_from and recv_msg, and then pass them into msg_handler, which returns a result or the message to be sent in the next round.

loop {
    // let (recv_from, recv_msg) = According to the last round of SendingMessages
    let recv_from = "".to_string();
    let recv_msg = vec![0u8];
    let sending_msg = keygen.msg_handler(recv_from, &recv_msg).unwrap();
    match sending_msg {
        SendingMessages::KeyGenSuccessWithResult(msg) => {
            // got the keygen result
            break;
        }
        _ => {
            // other sending messages, ref Step 2.
        }
    }
}

Once SendingMessages::KeyGenSuccessWithResult is received, it indicates completion.

• A local test shows how to use these functions.

• The usage of SignOffline, SignOnline are similar to KeyGen. Please ref here for more details.

References

• [DMZ+21] https://eprint.iacr.org/2022/297

Contact

You could reach us by email.

License

The OpenTSS library is licensed under the GNU General Public License v3.0.