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Open TSS LOGO

BuildLicense: GPLv3

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

Contact

You could reach us by email.

License

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