Subject: [bitcoin-dev] Taro: A Taproot Asset Representation Overlay

From: Olaoluwa Osuntokun <[email-masked]>
Date: Tue, 5 Apr 2022 11:06:03 -0400

Hi y'all,

I'm excited to publicly publish a new protocol I've been working on over the
past few months: Taro. Taro is a Taproot Asset Representation Overlay which
allows the issuance of normal and also collectible assets on the main
Bitcoin
chain. Taro uses the Taproot script tree to commit extra asset structured
meta
data based on a hybrid merkle tree I call a Merkle Sum Sparse Merkle Tree or
MS-SMT. An MS-SMT combined the properties of a merkle sum tree, with a
sparse
merkle tree, enabling things like easily verifiable asset supply proofs and
also efficient proofs of non existence (eg: you prove to me you're no longer
committing to the 1-of-1 holographic beefzard card during our swap). Taro
asset
transfers are then embedded in a virtual/overlay transaction graph which
uses a
chain of asset witnesses to provably track the transfer of assets across
taproot outputs. Taro also has a scripting system, which allows for
programmatic unlocking/transfer of assets. In the first version, the
scripting
system is actually a recursive instance of the Bitcoin Script Taproot VM,
meaning anything that can be expressed in the latest version of Script can
be
expressed in the Taro scripting system. Future versions of the scripting
system
can introduce new functionality on the Taro layer, like covenants or other
updates.

The Taro design also supports integration with the Lightning Network
(BOLTs) as
the scripting system can be used to emulate the existing HTLC structure,
which
allows for multi-hop transfers of Taro assets. Rather than modify the
internal
network, the protocol proposes to instead only recognize "assets at the
edges",
which means that only the sender+receiver actually need to know about and
validate the assets. This deployment route means that we don't need to
build up
an entirely new network and liquidity for each asset. Instead, all asset
transfers will utilize the Bitcoin backbone of the Lightning Network, which
means that the internal routers just see Bitcoin transfers as normal, and
don't
even know about assets at the edges. As a result, increased demand for
transfers of these assets as the edges (say like a USD stablecoin), which in
will turn generate increased demand of LN capacity, result in more
transfers, and
also more routing revenue for the Bitcoin backbone nodes.

The set of BIPs are a multi-part suite, with the following breakdown:
 * The main Taro protocol:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro.mediawiki
 * The MS-SMT structure:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro-ms-smt.mediawiki
 * The Taro VM:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro-vm.mediawiki
 * The Taro address format:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro-addr.mediawiki
 * The Taro Universe concept:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro-universe.mediawiki
 * The Taro flat file proof format:
https://github.com/Roasbeef/bips/blob/bip-taro/bip-taro-proof-file.mediawiki

Rather than post them all in line (as the text wouldn't fit in the allowed
size
limit), all the BIPs can be found above.

-- Laolu