What Is Bison Labs? A Guide to the New Sovereign Rollup on Bitcoin

Discover Bison Labs, a Layer 2 network that is scaling Bitcoin with sovereign rollups, and learn how it could impact the ecosystem.

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Bitcoin Layers


Elizabeth Olson


March 25, 2024

Bison Labs, a new sovereign rollup on Bitcoin, launched on testnet in March 2024. It has joined many other Layer 2 projects competing to scale Bitcoin effectively. 

In this guide, we will introduce Bison Labs and how it works.  

What Is Bison Labs?

Bison Labs is a Layer 2 (L2) network that aims to improve Bitcoin’s efficiency and speed using zero-knowledge (ZK) sovereign rollups. It also increases utility by enabling smart contract functionality on Bitcoin. Thus, developers can build a wide range of applications on Bison Labs, which the Bitcoin blockchain will secure. 

Bison Labs utilizes the Ordinals protocol as its data layer. As a result, rollup proofs and network statuses will be inscribed on Bitcoin, allowing them to be immutable and publicly accessible. 

Ordinals is a Bitcoin-native protocol rolled out in 2023 that enables anyone to embed (inscribe) data directly on the Bitcoin blockchain. 

In March 2024, Bison Labs closed a pre-seed funding round led by Portal Ventures. Other financial backers in this round were UTXO, Bitcoin Startup Labs, Waterdrip Capital, and Domo, the creator of the BRC-20 token standard.

What Are Sovereign Rollups?

Rollups are L2 scaling solutions that minimize congestion and move computations off the main chain. They then batch multiple transactions and generate proofs to certify their correctness. 

Sovereign rollups can be used by blockchains that don’t support smart contracts, such as Bitcoin. This type of rollup uses the main chain as the Data Availability (DA) and consensus layer but operates as its own settlement layers. This means sovereign rollups execute and settle their own transactions. 

When a proof is submitted to the DA layer, nodes are responsible for validating its accuracy. Rollups can be designed to produce ZK or fraud proofs. ZK proofs demonstrate the validity of transactions immediately, while fraud proofs, used by Optimistic rollups, provide a dispute opportunity for anyone to challenge the correctness of a transaction. 

How Does Bison Labs Work?

Here are the various components that enable Bison Labs to operate.  


Bison Labs uses a ZK-STARK sovereign rollup to scale Bitcoin. ZK-STARK, also known as Zero-Knowledge Scalable Transparent Argument of Knowledge, is a proofing system created by the software company Starkware. It offers scalability and privacy to Bison users. 

The rollup processes multiple transactions off-chain and batches them into compressed bundles. A single ZK proof is then used to confirm the validity of the bundled transactions on-chain.

In addition to ZK proofs, Bison Labs features human-readable raw proofs containing users’ messages and signatures. The goal of raw proof is to offer straightforward verification of status changes. The ZK-STARK proofing system is responsible for confirming that all raw proofs are validated.

The Prover & Verifier

Bison’s ZK-STARK rollup uses specialized software modules known as a prover and verifier. The prover generates ZK proofs from raw proofs and demonstrates to the verifier that they are correct without revealing transaction details. 

Bison’s ZK-STARK proofing system supports self-verification, which means users can become their own validators. Bison’s goal is to complete self-verification within one second.

ZK proofs occupy less block space than complete transactional data, reducing computational costs, and increasing transaction speeds and privacy of a user. 

Bison OS

Bison OS is Bison Labs' central framework. It consists of sequencers and token contracts. All messages and transactions on Bison are first received by the sequencer node and then processed in the order in which they are received. 

Token contracts are smart contracts that carry out status (balance and address data) updates and maintain token balances. They receive messages from the sequencer, prompting them to execute the appropriate action. 

Furthermore, Bison token contracts have API interfaces to allow users to query them directly. Token contracts on Bison Labs are created to perform different functions, such as swapping and bridging, and are powered by ZK-STARK technology. 

L2 dApp

The Bison L2 dApp is a smart contract-powered application that acts as the user interface. It allows users to request swap price quotes and conduct actual token swaps. Users can interact directly with the L2 dApp or through a sequencer. 

In the first step of this process, the user prompts the Bison API to generate a swap price quote. Once this quote is provided, the user can utilize it to create an actual swap message, which is then sent to the sequencer. 

Next, the sequencer sends the message to the L2 dApp. If the price is acceptable, the L2 dApp signs the message and sends it to the smart contract, which executes the swap and updates wallet balances. A zero-knowledge proof is then produced and verified before being inscribed on the Bitcoin blockchain using the Ordinals protocol.


The Bison bridge enables the “transfer” of BTC, BRC-20 tokens, and Ordinal inscriptions to and from the base layer. When a user is bridging from Bitcoin, their BTC is locked in multiple multisig wallets, which also function as Discreet Log Contracts (DLCs). This prompts the bridging smart contract on Bison to mint an equivalent amount of bisonBTC. 

Using this bridged version of BTC, the user can interact with various dApps on the Layer 2 network until they are ready to move back to Layer 1 (L1).

When moving BTC back to L1, the user must sign a message to trigger the DLC to unlock their funds. A DLC is a Bitcoin transaction that uses data from oracles (entities that transmit off-chain data to blockchains) to execute smart contracts. It provides a trustless bridging process by eliminating the need for a trusted entity to custody assets. 

For each L1 asset, Bison has a corresponding DLC with trigger events that allow users to spend on L2, exit to L1, and auto-unlock BTC after a specified period of inactivity. 

What is Bison Labs’ Vision for Bitcoin?

Bison Labs wants to enhance the DeFi ecosystem by leveraging Bitcoin's untapped benefits, such as security, reliability, and decentralization. It is utilizing ZK-STARK technology to bring smart contract functionality to Bitcoin. 

As a result, developers can build DeFi applications on Bitcoin, allowing users to perform a wide range of financial activities safeguarded by the most secure blockchain today.

Bison’s ZK-STARK rollup also promises to scale Bitcoin by improving transaction throughput and minimizing transaction fees. When multiple transactions are “rolled up” into compressed bundles, Bison is able to settle more transactions at any given time. Batching also distributes fees across all the bundled transactions, lowering users' costs. 

What’s Next for Bison Labs?

Bison Labs is in the testnet stage of development. The Bison Labs team plans to integrate Stakware’s Cairo Virtual Machine (VM) as this effort continues. This will enable Bison to use the software company’s infrastructure for ZK-STARK proofs and enhance Bison’s smart contract functionality. Bison Labs is also considering upgrading to Starkware’s new prover

Although the mainnet launch date has not yet been announced at this time, Bison Lab's vision for Bitcoin could propel it into one of the most anticipated upcoming Layer 2 networks in 2024, especially because it leverages the Ordinals protocol as a DA layer. 

Xverse: Your Gateway to Web3 Built on Bitcoin

Xverse is a Web3 wallet for the Bitcoin ecosystem, supporting BTC, Ordinals, BRC-20 Runes, and a range of other assets. You can also use Xverse to swap and bridge tokens on the Bison testnet network. 

Additionally, developers can utilize Xverse’s Sats Connect API to connect their Bison decentralized applications to Xverse. Click this link to learn how to integrate Sats Connect with your Bison dApp.

Download Xverse today to explore the exciting world of Bitcoin Layer 2s.

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