Fractal
Overview
Status
Mainnet
Type
Alt. Chain
Fee Token
FB
BTC Supply
Unavailable
Fractal is a Bitcoin sidechain purpose built to scale bitcoin-native applications like Runes and BRC-20s. It leverages a novel consensus mechanism similar to merge-mining.
CUSTODY
DATA AVAILABILITY
OPERATORS
FINALITY ASSURANCE
Trust Assumption Review
BTC Custody
Very High
🛑
Bool bBTC
Fractal relies on a third party for bridge infrastructure
Fractal’s asset bridge between Bitcoin and Fractal is managed by a third party, Bool Network. Bool Network is responsible for custodying the bitcoin assets that back BTC on Fractal.
⚠️ The code behind Bool Network’s bridge is not open-source. We do not know the signing mechanism, or who the signers are, for the Bool Network.
⚠️ If a fraudulent withdrawal was processed by the bridge operator, users would have no way to challenge it. Bridge operators can steal funds.
⚠️ The code behind Bool Network’s bridge is not open-source. We do not know the signing mechanism, or who the signers are, for the Bool Network.
⚠️ If a fraudulent withdrawal was processed by the bridge operator, users would have no way to challenge it. Bridge operators can steal funds.
Data Availability
Medium
⚠️
DA requirement satisfied by Fractal full nodes
The data availability requirement is satisfied by sidechain full nodes. Fractal’s node software is open-source, and anyone can run a full node to verify the current state of the chain.
Like any sidechain, sidechain blocks can be orphaned, so miners are disincentivized to withhold data and not broadcast their blocks as they would not receive mining rewards.
Like any sidechain, sidechain blocks can be orphaned, so miners are disincentivized to withhold data and not broadcast their blocks as they would not receive mining rewards.
Block Production
Medium
⚠️
Blocks are produced by two distinct miner sets
Fractal inherits probabilistic finality from its operator set. It implements a mining mechanism called “cadence mining” that sees every ⅓ blocks merge-mined by bitcoin miners, and ⅔ blocks mined by miners running Fractal’s mining software. This sees Fractal run two different mining algorithms catered to two different operator sets.
Fractal blocks are considered finalized after a sufficient amount of hashrate has built on top of the longest chain.
Fractal blocks are considered finalized after a sufficient amount of hashrate has built on top of the longest chain.
Finality Guarantees
Medium
⚠️
Fractal full nodes validate proposed blocks
Fractal state transitions are validated by its miner set. After a block is mined by a Fractal miner, it is broadcast to its full node set who validates the block and includes it in the chain.
Bitcoin Security
Fractal is partially merge-mined
Fractal is partially secured by bitcoin miners who merge-mine fractal as a part of its cadence mining set up.
MEV not directly on bitcoin
Fractal does not leak MEV to bitcoin directly. Bitcoin miners may take advantage of opportunities to extract MEV if the network is experiencing high activity.
Alternative token used for fees and to incentivize miners
Fees on Fractal are paid in FB tokens. Token issuance is paid out in FB tokens to incentivized miners.
Merge-mining enables Bitcoin miners to earn more fees
Fractal contributes to Bitcoin's security budget indirectly by providing Bitcoin miners an opportunity to earn fee revenue via merge-mining.
Additional Considerations
The Fractal blockchain is growing at a fast rate
The Fractal blockchain is growing at a rate much faster than that of Bitcoin. As the blockchain continues to grow, it becomes more difficult for users to run Fractal full nodes. This might see the majority of users pass on the data availability requirement onto another party.
🚨 Project is not a sidesystem
This project will be moved to the Alternative category
Projects that do not meet our requirements to be considered a sidesystem will be moved to the Alternative category. They have until June 30th to implement the technical requirements to be considered a sidesystem.
Withdrawals
Users trust sidechain consensus and third party bridge providers with withdrawals
Withdrawals from Fractal, like any sidechain, users would need to trust the operators of the Fractal chain and the bridge operator, the Bool Network, to process their withdrawal transaction and release funds on the Bitcoin mainchain.
Technology
Bitcoin Script
Bitcoin Script is bitcoin’s scripting language that enables users to define the conditions under which a Bitcoin UTXO can be spent. It is a low-level Assembly-based programming language.
Fractal is based on Bitcoin Script.
Fractal is based on Bitcoin Script.
OP_CAT
OP_CAT is a Bitcoin opcode, short for Operation Concatenate. It allows the combination of two data elements on the Bitcoin stack. The opcode was originally introduced by Satoshi Nakamoto, but was removed due to potential denial of service attack vectors.
OP_CAT would enable more expressive smart contracts on bitcoin, including “covenants”, a way to set spending conditions on individual UTXOs. Teams are also reviewing how it can support SNARK verification in Script, which would further improve bridging L1 assets to second layer protocols.
OP_CAT would enable more expressive smart contracts on bitcoin, including “covenants”, a way to set spending conditions on individual UTXOs. Teams are also reviewing how it can support SNARK verification in Script, which would further improve bridging L1 assets to second layer protocols.
Merge-mining
Merged mining is a feature of Fractal’s consensus mechanism that allows coupling between bitcoin and Fractal. Essentially, BTC mining pools add references to Fractal blocks in mining jobs sent to mining participants. Additionally, because the Fractal mining algorithm is the same as bitcoin’s, there is little added energy expenditure. This sees bitcoin miners have an ability to additionally mine a percentage of Fractal blocks. Miners are incentivized through earning a portion of transaction fees and newly issued tokens to mine Fractal.
Cadence mining
Cadence mining is a novel mining mechanism that sees ⅓ of Fractal blocks mined by bitcoin miners who merge-mine Fractal, and ⅔ of Fractal blocks mined by its own miner set. Thus, the security of Fractal mining is dependent on two distinct operator sets.
Bitcoin miners who want to merge-mine Fractal point some of their hashrate to secure the Fractal chain. Fractal miners run a distinct mining software that sees them leverage a different difficulty adjustment.
Bitcoin miners who want to merge-mine Fractal point some of their hashrate to secure the Fractal chain. Fractal miners run a distinct mining software that sees them leverage a different difficulty adjustment.
Use Cases
Ordinals, Runes, & BRC-20 trading
Due to having a similar scripting language as the Bitcoin mainchain, Fractal provides users with similar applications for Ordinals and BRC-20 token trading as the Bitcoin L1.
Testing ground for new opcodes
Since Fractal has enabled opcodes that are not yet live on Bitcoin, developers can deploy applications there to preview what it would be like on Bitcoin. This includes analyzing the builder experience, potential security vulnerabilities, and presenting how these changes might permanently affect the Bitcoin network.
Source Code
Code is open-source
The source code for Fractal's node implementation is open-source.
Knowledge Bits
Learn more