Broly is a POC that enables users to create Bitcoin inscriptions via Starknet without owning BTC or interacting directly with the Bitcoin network – securely, easily, and in a trust-minimized way. Broly runs an order book of inscription requests on Starknet, handles the Bitcoin transactions in the background, and uses smart contracts to prove that the transactions are valid.
Broly was developed by the Exploration team at StarkWare – the technology company that is Starknet’s main contributor – for the benefit of the Bitcoin dev community. Broly enables Bitcoin devs to trustlessly create inscriptions in their applications with the best UX possible, paving the way for devs to build many new experiences and use cases. Broly also demonstrates the benefits of the Utu Relay and Raito open source libraries, which are discussed below.
How Broly works
Broly allows users to prove statements about inscriptions, including the validity of inscribed data and the ownership of an inscription. For those who are less familiar with Bitcoin’s ecosystem, inscriptions are similar to NFTs – data attached to satoshis, which are unique and numbered. The owner of a satoshi also owns the data that is inscribed on it. The Broly experience for inscriptions is designed to resemble the simplicity and freedom of applications like pump.fun, a Solana-based platform that allows users to easily trade and create assets, tokens or NFTs. In this way, Broly allows app devs to easily build pump.fun experiences for Bitcoin with inscriptions.
To use Broly, the requester, who doesn’t need any BTC on the Bitcoin network, broadcasts a request to get their data inscribed on Bitcoin. A submitter running the inscriber service accepts the request, inscribes the data on Bitcoin, and transfers it to the requester’s Bitcoin address. The submitter can then submit the inscription and transfer transactions to the Broly contract on Starknet and obtain full verification of the validity of the transaction’s execution, transaction inclusion in the block, and inclusion of the block on the canonical Bitcoin chain.
Use cases for Broly POC and related dev libraries
The capabilities unlocked by Broly’s validation of certain statements about Bitcoin transactions and Bitcoin wallets are vast. This is thanks to a powerful library written in Cairo and deployed on Starknet called Utu Relay. Utu Relay, created by web3-focused company LFG Labs, is a smart contract that enables verification of Bitcoin transactions and events. Outside of Utu Relay, there is no other provable method of verifying transactions on Bitcoin except on Bitcoin itself.
Through Utu Relay, users can submit the headers of the canonical Bitcoin chain and dispute them with a longer chain that comprises more proof of work. Using Merkle proofs, users can also write a contract that will check that a transaction is indeed part of a block. In this way, Utu Relay allows for optimistic disputes. This system will eventually minimize trust when rewards for disputing “bad” chains are implemented for Utu Relay.
Utu Relay functions like a storage proof and allows different properties of the Bitcoin blockchain to be queried. For example, a user can confirm that someone is the owner of a particular Broly-created inscription using Utu Relay. The tool can also be used to prove solvency, the balance or activity history of a wallet, or a wallet’s history for the purpose of airdrops. Utu Relay can also be used to give early platform access to wallets that have made transactions in multiple ecosystems, not just Bitcoin. Using Utu Relay, for example, a user could prove that he or she had made over 100 transactions cumulatively on Ethereum and Bitcoin by early 2017. OG vibes!
Another use case is a project in development that allows users to mint Bitcoin badges. This experimental project, built on top of the Broly and Utu Relay infrastructure, allows users to create digital badges based on provable facts or milestones from their historical Bitcoin transaction activity. For instance, a badge might certify that a wallet was active before a certain date or interacted with a specific type of protocol. The key innovation is that these badges are not self-claimed; they can be trusted, as they are based on cryptographic proofs that Utu Relay helps verify. In addition to being great fun, these badges can assert credibility and could be used as collateral for loans, to prove solvency, and more.
Another useful open source library that Broly is based on is Raito, a Bitcoin consensus light client written in Cairo and developed by the StarkWare Exploration team, which implements the same validation logic as Bitcoin core. Raito is a way to run Bitcoin’s consensus rules in a provable way on Starknet by providing a state between two checkpoints. It allows a system to verify Bitcoin state transitions – like block headers, Merkle roots, or UTXO status – directly within a smart contract on Starknet, eliminating the need for centralized oracles or trusted relayers.
With Raito, instead of a user needing to trust that someone gave them the correct Bitcoin chain state, or re-run the entire transaction history of Bitcoin, the user can verify a STARK proof. Because Raito compresses Bitcoin’s block validation quickly and trustlessly, verification of the proof is faster than the reexecution of the computation. In the future, this could be a game-changer for building faster syncs among nodes, which currently require hours or even days to sync; making Bitcoin light wallets faster and more secure; and even offering meta-protocol indexers, such as Ordinals, RGB, or Taproot Assets, a decentralized indexing model whereby different clients could verify inscriptions or asset states without rerunning full chain validation themselves.
Broly as part of Starknet’s Bitcoin vision
While Bitcoin has revolutionized the way people think about money and trust, today most BTC sits static in wallets and exchanges, constrained by the network’s lack of scalability and inability to natively support complex applications. Starknet seeks to unleash Bitcoin’s full potential, while preserving its core principles. As a Layer 2 above Bitcoin, Starknet will become Bitcoin’s execution layer, aiming to bring and serve one billion Bitcoin users, introducing improved UX, and trustlessly scaling Bitcoin to thousands of transactions per second (TPS). In the same way that Starknet has brought Ethereum massive scalability with STARK proofs, Starknet aims to bring Bitcoin the same benefits with zero compromises on security and decentralization.
Starknet’s development of the Broly POC showcases its Bitcoin integration vision, as Broly allows Starknet to work seamlessly with Bitcoin, without requiring users to own BTC or Bitcoin wallets, or even operate on the Bitcoin network. Now it is open for Bitcoin app devs who want to provide their users with rich experiences on Bitcoin without needing to worry about scale, trustlessness and security.
Final thoughts
The Broly POC brings the concept of storage proofs to Bitcoin on Starknet and it can inspire many interesting use cases for teams that are interested in building on Bitcoin, but have been stymied by the network’s limitations. If you are a developer or a builder looking to start building on Bitcoin, the possibilities with Broly, and the underlying Utu Relay and Raito libraries, are endless.
To learn more about using Broly, check out the full Broly demo video below, as well as the relevant Broly, Utu Relay, and Raito Github pages. The StarkWare Exploration team’s Github site, Keep Starknet Strange, is the best place to learn about all the team’s exciting projects. You can also check out Starknet’s devs hub and dApps ecosystem. Also, be sure to follow Starknet on X for the latest news and announcements. Lastly, delve into Starknet’s vision for Bitcoin integration.
