MuSig2CombineSig

MuSig2CombineSig (experimental!) combines the given partial signature(s) with the local one, if it already exists. Once a partial signature of all participants is registered, the final signature will be combined and returned.

NOTE: The MuSig2 BIP is not final yet and therefore this API must be considered to be HIGHLY EXPERIMENTAL and subject to change in upcoming releases. Backward compatibility is not guaranteed!

Source: signrpc/signer.proto

gRPC

rpc MuSig2CombineSig (MuSig2CombineSigRequest) returns (MuSig2CombineSigResponse);

REST

HTTP Method	Path
POST	/v2/signer/musig2/combinesig

Code Samples

gRPC

Javascript

const fs = require('fs');
const grpc = require('@grpc/grpc-js');
const protoLoader = require('@grpc/proto-loader');

const GRPC_HOST = 'localhost:10009'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
const TLS_PATH = 'LND_DIR/tls.cert'

const loaderOptions = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
};
const packageDefinition = protoLoader.loadSync(['lightning.proto', 'signrpc/signer.proto'], loaderOptions);
const signrpc = grpc.loadPackageDefinition(packageDefinition).signrpc;
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA';
const tlsCert = fs.readFileSync(TLS_PATH);
const sslCreds = grpc.credentials.createSsl(tlsCert);
const macaroon = fs.readFileSync(MACAROON_PATH).toString('hex');
const macaroonCreds = grpc.credentials.createFromMetadataGenerator(function(args, callback) {
  let metadata = new grpc.Metadata();
  metadata.add('macaroon', macaroon);
  callback(null, metadata);
});
let creds = grpc.credentials.combineChannelCredentials(sslCreds, macaroonCreds);
let client = new signrpc.Signer(GRPC_HOST, creds);
let request = {
  session_id: <bytes>,
  other_partial_signatures: <bytes>,
};
client.muSig2CombineSig(request, function(err, response) {
  console.log(response);
});
// Console output:
//  {
//    "have_all_signatures": <bool>,
//    "final_signature": <bytes>,
//  }

Python

import codecs, grpc, os
# Generate the following 2 modules by compiling the signrpc/signer.proto with the grpcio-tools.
# See https://github.com/lightningnetwork/lnd/blob/master/docs/grpc/python.md for instructions.
import signer_pb2 as signrpc, signer_pb2_grpc as signerstub

GRPC_HOST = 'localhost:10009'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_DIR/tls.cert'

# create macaroon credentials
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
def metadata_callback(context, callback):
  callback([('macaroon', macaroon)], None)
auth_creds = grpc.metadata_call_credentials(metadata_callback)
# create SSL credentials
os.environ['GRPC_SSL_CIPHER_SUITES'] = 'HIGH+ECDSA'
cert = open(TLS_PATH, 'rb').read()
ssl_creds = grpc.ssl_channel_credentials(cert)
# combine macaroon and SSL credentials
combined_creds = grpc.composite_channel_credentials(ssl_creds, auth_creds)
# make the request
channel = grpc.secure_channel(GRPC_HOST, combined_creds)
stub = signerstub.SignerStub(channel)
request = signrpc.MuSig2CombineSigRequest(
  session_id=<bytes>,
  other_partial_signatures=<bytes>,
)
response = stub.MuSig2CombineSig(request)
print(response)
# {
#    "have_all_signatures": <bool>,
#    "final_signature": <bytes>,
# }

REST

Javascript

const fs = require('fs');
const request = require('request');

const REST_HOST = 'localhost:8080'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'

let requestBody = {
  session_id: <string>, // <bytes> (base64 encoded)
  other_partial_signatures: <array>, // <bytes> (base64 encoded)
};
let options = {
  url: `https://${REST_HOST}/v2/signer/musig2/combinesig`,
  // Work-around for self-signed certificates.
  rejectUnauthorized: false,
  json: true,
  headers: {
    'Grpc-Metadata-macaroon': fs.readFileSync(MACAROON_PATH).toString('hex'),
  },
  form: JSON.stringify(requestBody),
}
request.post(options, function(error, response, body) {
  console.log(body);
});
// Console output:
//  {
//    "have_all_signatures": <boolean>, // <bool> 
//    "final_signature": <string>, // <bytes> 
//  }

Python

import base64, codecs, json, requests

REST_HOST = 'localhost:8080'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_DIR/tls.cert'

url = f'https://{REST_HOST}/v2/signer/musig2/combinesig'
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
headers = {'Grpc-Metadata-macaroon': macaroon}
data = {
  'session_id': base64.b64encode(<bytes>),
  'other_partial_signatures': base64.b64encode(<bytes>),
}
r = requests.post(url, headers=headers, data=json.dumps(data), verify=TLS_PATH)
print(r.json())
# {
#    "have_all_signatures": <bool>,
#    "final_signature": <bytes>,
# }

Shell

# There is no CLI command for this RPC

Messages

signrpc.MuSig2CombineSigRequest

Source: signrpc/signer.proto

Field	gRPC Type	REST Type	REST Placement
session_id The unique ID of the signing session to combine the signatures for.	bytes	string	body
other_partial_signatures The list of all other participants' partial signatures to add to the current session.	bytes[]	array	body

signrpc.MuSig2CombineSigResponse

Source: signrpc/signer.proto

Field	gRPC Type	REST Type
have_all_signatures Indicates whether all partial signatures required to create a final, full signature are known yet. If this is true, then the final_signature field is set, otherwise it is empty.	bool	boolean
final_signature The final, full signature that is valid for the combined public key.	bytes	string