Universes

Learn how to run a universe and connect to other universes.

In the context of Taproot Assets, a universe is a service that acts as a repository for publicly minted assets. It contains knowledge of assets, mints, metadata, public transfers and their proofs. A universe is required for users to fetch data necessary to validate transfers, and may be public or private.

Anyone may run a universe, or use one or multiple universes provided by others, such as Lightning Labs.

Your local universe

When running tapd, you will run a private universe by default. In this mode, all RPC calls to the universe require authentication using the tapd macaroon. To disable macaroon authentication for the QueryProof and InsertProof RPC calls, you may set the following configuration flag:

allow-public-uni-proof-courier=true

You may further open up your local universe to serve the QueryAssetStats , UniverseStats and QueryEvents RPC calls:

allow-public-stats=true

You may do this to operate a public universe, or make it easier for other applications to reach your API endpoints.

Running a public universe

Running a universe is as simple as running tapd and amending your configuration file. You may run a universe over RPC or REST. By default, tapd is expected to listen on gRPC TCP port 10029 and REST TCP port 8089 , so ensure this port is open on your machine if you would like others to connect to you. Being publicly reachable is not a requirement for a universe, however. Your universe may only serve resources on a private network, or be otherwise restricted.

When running tapd as part of litd, you may also use port 8443 or define your own port. For example, as the REST universe is also usable through a browser over HTTPS, you may configure it over port 443 or set up a proxy.

Sampletapd.conf file:

rpclisten=0.0.0.0:10029 restlisten=0.0.0.0:8089 allow-public-uni-proof-courier=true allow-public-stats=true universe.public-access=rw

You can verify whether your universe is accepting proofs with the command tapcli universe federation config info

{
    "global_sync_configs": [
        {
            "proof_type": "PROOF_TYPE_ISSUANCE",
            "allow_sync_insert": true,
            "allow_sync_export": true
        },
        {
            "proof_type": "PROOF_TYPE_TRANSFER",
            "allow_sync_insert": true,
            "allow_sync_export": true
        }
    ],
    "asset_sync_configs": []
}

You can change the configuration from the CLI using tapcli universe federation config global --proof_type issuance --allow_insert true and again with the --proof_type transfer flag

The default universe

By default, your tapd will connect to the default universe, for instance testnet.universe.lightning.finance:10029 for testnet, or universe.lightning.finance:10029 on mainnet.

The contents of the default universe are also available via a public REST API:

https://universe.lightning.finance/v1/taproot-assets/universe/rootsuniverse.lightning.finance

You may also make use of the UI available through Lightning Terminal

Assets - Lightning Terminal

Federations

By default, your tapd instance will connect to a default universe. You can manually add additional universes to sync to and from, called a federation. You can see this federation with tapcli universe federation list.

If you would like to add a universe to this federation, you can do this on with tapcli universe federation add --universe_host <universe_ip:port>

Similarly, you can remove universes from this federation with tapcli universe federation del --universe_host <universe_ip>:port

Tapping into Taproot Assets #4: Join a Universe Federation

Syncing to a universe

By default, your tapd will sync to universes which have configured in your local federation, and only for assets which you either hold or have created a taproot address for. You may also manually sync specific asset IDs or group keys.

tapcli universe sync --universe_host <universe_ip:port> --group_key <group key>

To configure your tapd to regularly sync to other asset IDs or group keys, you may use the universe federation configuration. The config global options will apply to all assets, while the config local options will only apply to specific assets.

tapcli universe federation config global --proof_type issuance --allow_insert true

tapcli universe federation config local --proof_type transfer --allow_insert true --group_key <group key>

The Universe APIs

A Taproot Asset Universe is available over gRPC and REST on the default ports. You may run your own universe or interact with a public universe. Public universes are unauthenticated, the macaroon checks are skipped.

For instance, when making a transfer, the proofs may be pushed to one or multiple universes using the REST API. This requires the asset ID, the leaf key index and script key.

/v1/taproot-assets/universe/proofs/asset-id/{key.id.asset_id_str}/{key.leaf_key.op.hash_str}/{key.leaf_key.op.index}/{key.leaf_key.script_key_str}

A detailed list of all available fields as well as code examples can be found under the Taproot Assets Universe API documentation.