AnchorVirtualPsbts

AnchorVirtualPsbts merges and then commits multiple virtual transactions in a single BTC level anchor transaction. This RPC should be used if the BTC level anchor transaction of the assets to be spent are encumbered by a normal key and don't require any special spending conditions. For any custom spending conditions on the BTC level, the two RPCs CommitVirtualPsbts and PublishAndLogTransfer should be used instead (which in combination do the same as this RPC but allow for more flexibility).

Source: assetwalletrpc/assetwallet.proto

gRPC

rpc AnchorVirtualPsbts (AnchorVirtualPsbtsRequest) returns (SendAssetResponse);

REST

HTTP Method	Path
POST	/v1/taproot-assets/wallet/virtual-psbt/anchor

Code Samples

gRPC

Javascript

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

const GRPC_HOST = 'localhost:10029'
const MACAROON_PATH = 'TAPROOT-ASSETS_DIR/regtest/taproot-assets.macaroon'
const TLS_PATH = 'TAPROOT-ASSETS_DIR/tls.cert'

const loaderOptions = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
};
const packageDefinition = protoLoader.loadSync('assetwalletrpc/assetwallet.proto', loaderOptions);
const assetwalletrpc = grpc.loadPackageDefinition(packageDefinition).assetwalletrpc;
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 assetwalletrpc.AssetWallet(GRPC_HOST, creds);
let request = {
  virtual_psbts: <bytes>,
};
client.anchorVirtualPsbts(request, function(err, response) {
  console.log(response);
});
// Console output:
//  {
//    "transfer": <AssetTransfer>,
//  }

Python

import codecs, grpc, os
# Generate the following 2 modules by compiling the assetwalletrpc/assetwallet.proto with the grpcio-tools.
# See https://github.com/lightningnetwork/lnd/blob/master/docs/grpc/python.md for instructions.
import assetwallet_pb2 as assetwalletrpc, assetwallet_pb2_grpc as assetwalletstub

GRPC_HOST = 'localhost:10029'
MACAROON_PATH = 'TAPROOT-ASSETS_DIR/regtest/taproot-assets.macaroon'
TLS_PATH = 'TAPROOT-ASSETS_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 = assetwalletstub.AssetWalletStub(channel)
request = assetwalletrpc.AnchorVirtualPsbtsRequest(
  virtual_psbts=<bytes>,
)
response = stub.AnchorVirtualPsbts(request)
print(response)
# {
#    "transfer": <AssetTransfer>,
# }

REST

Javascript

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

const REST_HOST = 'localhost:8089'
const MACAROON_PATH = 'TAPROOT-ASSETS_DIR/regtest/taproot-assets.macaroon'

let requestBody = {
  virtual_psbts: <array>, // <bytes> (base64 encoded)
};
let options = {
  url: `https://${REST_HOST}/v1/taproot-assets/wallet/virtual-psbt/anchor`,
  // 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:
//  {
//    "transfer": <object>, // <AssetTransfer> 
//  }

Python

import base64, codecs, json, requests

REST_HOST = 'localhost:8089'
MACAROON_PATH = 'TAPROOT-ASSETS_DIR/regtest/taproot-assets.macaroon'
TLS_PATH = 'TAPROOT-ASSETS_DIR/tls.cert'

url = f'https://{REST_HOST}/v1/taproot-assets/wallet/virtual-psbt/anchor'
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
headers = {'Grpc-Metadata-macaroon': macaroon}
data = {
  'virtual_psbts': base64.b64encode(<bytes>),
}
r = requests.post(url, headers=headers, data=json.dumps(data), verify=TLS_PATH)
print(r.json())
# {
#    "transfer": <AssetTransfer>,
# }

Shell

# There is no CLI command for this RPC

Messages

assetwalletrpc.AnchorVirtualPsbtsRequest

Source: assetwalletrpc/assetwallet.proto

Field	gRPC Type	REST Type	REST Placement
virtual_psbts The list of virtual transactions that should be merged and committed to in the BTC level anchor transaction.	bytes[]	array	body

taprpc.SendAssetResponse

Source: taprootassets.proto

Field	gRPC Type	REST Type
transfer	AssetTransfer	object

Nested Messages

taprpc.AssetTransfer

Field	gRPC Type	REST Type
transfer_timestamp	int64	string
anchor_tx_hash The new transaction that commits to the set of Taproot Assets found at the above new anchor point.	bytes	string
anchor_tx_height_hint	uint32	integer
anchor_tx_chain_fees	int64	string
inputs Describes the set of spent assets.	TransferInput[]	array
outputs Describes the set of newly created asset outputs.	TransferOutput[]	array

taprpc.TransferInput

Field	gRPC Type	REST Type
anchor_point The old/current location of the Taproot Asset commitment that was spent as an input.	string	string
asset_id The ID of the asset that was spent.	bytes	string
script_key The script key of the asset that was spent.	bytes	string
amount The amount of the asset that was spent.	uint64	string

taprpc.TransferOutput

Field	gRPC Type	REST Type
anchor	TransferOutputAnchor	object
script_key	bytes	string
script_key_is_local	bool	boolean
amount	uint64	string
new_proof_blob The new individual transition proof (not a full proof file) that proves the inclusion of the new asset within the new AnchorTx.	bytes	string
split_commit_root_hash	bytes	string
output_type	OutputType	string
asset_version	AssetVersion	string

taprpc.TransferOutputAnchor

Field	gRPC Type	REST Type
outpoint The new location of the Taproot Asset commitment that was created on chain.	string	string
value	int64	string
internal_key	bytes	string
taproot_asset_root	bytes	string
merkle_root	bytes	string
tapscript_sibling	bytes	string
num_passive_assets	uint32	integer

Enums

taprpc.AssetVersion

Name	Number
ASSET_VERSION_V0 ASSET_VERSION_V0 is the default asset version. This version will include the witness vector in the leaf for a tap commitment.	0
ASSET_VERSION_V1 ASSET_VERSION_V1 is the asset version that leaves out the witness vector from the MS-SMT leaf encoding.	1

taprpc.OutputType

Name	Number
OUTPUT_TYPE_SIMPLE OUTPUT_TYPE_SIMPLE is a plain full-value or split output that is not a split root and does not carry passive assets. In case of a split, the asset of this output has a split commitment.	0
OUTPUT_TYPE_SPLIT_ROOT OUTPUT_TYPE_SPLIT_ROOT is a split root output that carries the change from a split or a tombstone from a non-interactive full value send output. In either case, the asset of this output has a tx witness.	1