BOB
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About
BOB (Build on Bitcoin) is an OP Stack rollup that aims to natively support the Bitcoin stack. The current implementation supports a variety of canonical and external bridging for BTC-related assets and a tBTC-v2 LightRelay smart contract for verifying... Bitcoin transaction proofs through their blocks' headers on the L2.
Badges
About
BOB (Build on Bitcoin) is an OP Stack rollup that aims to natively support the Bitcoin stack. The current implementation supports a variety of canonical and external bridging for BTC-related assets and a tBTC-v2 LightRelay smart contract for verifying... Bitcoin transaction proofs through their blocks' headers on the L2.
Phase 1: Optimistic BOB
2024 May 1st
BOB bootstrapping as an Optimistic Rollup on Ethereum.
Funds can be stolen if
Funds can be frozen if
MEV can be extracted if
Sequencer failure
Self sequenceState validation
NoneCurrently the system permits invalid state roots. More details in project overview.
Exit window
NoneThere is no window for users to exit in case of an unwanted regular upgrade since contracts are instantly upgradable.
Proposer failure
Cannot withdrawOnly the whitelisted proposers can publish state roots on L1, so in the event of failure the withdrawals are frozen.
BOB is a Fraud proofs are not enabled
OP Stack projects can use the OP fault proof system, already being deployed on some. This project though is not using fault proofs yet and is relying on the honesty of the permissioned Proposer and Challengers to ensure state correctness. The smart contract system permits invalid state roots.
Funds can be stolen if an invalid state root is submitted to the system (CRITICAL).
All data required for proofs is published on chain
All the data that is used to construct the system state is published on chain in the form of cheap blobs or calldata. This ensures that it will be available for enough time.
The system has a centralized operator
The operator is the only entity that can propose blocks. A live and trustworthy operator is vital to the health of the system.
MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.
Users can force any transaction
Because the state of the system is based on transactions submitted on the underlying host chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the smart contract on the host chain directly.
Regular exit
The user initiates the withdrawal by submitting a regular transaction on this chain. When the block containing that transaction is finalized the funds become available for withdrawal on L1. The process of block finalization takes a challenge period of 7d to complete. Finally the user submits an L1 transaction to claim the funds. This transaction requires a merkle proof.
Funds can be frozen if the centralized validator goes down. Users cannot produce blocks themselves and exiting the system requires new block production (CRITICAL).
Forced exit
If the user experiences censorship from the operator with regular exit they can submit their withdrawal requests directly on L1. The system is then obliged to service this request or halt all withdrawals, including forced withdrawals from L1 and regular withdrawals initiated on L2. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.
EVM compatible smart contracts are supported
OP stack chains are pursuing the EVM Equivalence model. No changes to smart contracts are required regardless of the language they are written in, i.e. anything deployed on L1 can be deployed on L2.
The system uses the following set of permissioned addresses:
Challenger is an actor allowed to delete state roots proposed by a Proposer.
Guardian is an actor allowed to pause deposits and withdrawals.
Proposer is an actor allowed to post new state roots of current layer to the host chain.
- This is a Gnosis Safe with 4 / 6 threshold.
- Can act on behalf of ProxyAdmin.
- Is a Challenger.
- Can change configuration of SystemConfig - it can update the preconfer address, the batch submitter (Sequencer) address and the gas configuration of the system.
- Can change configuration of AddressManager (acting via ProxyAdmin) - set and change address mappings.
- Is a Guardian.
- Can upgrade implementation of L1StandardBridge (acting via ProxyAdmin) - upgrading the bridge implementation can give access to all funds escrowed therein.
- Can upgrade implementation of OptimismPortal, SystemConfig, L2OutputOracle (acting via ProxyAdmin).
Those are the participants of the BobMultisig.
Is a Sequencer.
Is a Proposer.
The system consists of the following smart contracts on the host chain (Ethereum):
Escrow for custom external tokens that use the canonical bridge for messaging but are governed externally. This contract stores the following tokens: wstETH.
- Can be used to configure AddressManager - set and change address mappings.
- Can be used to upgrade implementation of L1StandardBridge - upgrading the bridge implementation can give access to all funds escrowed therein.
- Can be used to upgrade implementation of OptimismPortal, SystemConfig, L2OutputOracle.
The main entry point to deposit ERC20 tokens from host chain to this chain. This contract can store any token. This contract can store any token.
Upgrade delay: No delay
Escrow for custom external tokens that use the canonical bridge for messaging but are governed externally. This contract stores the following tokens: USDC.
The main entry point to deposit funds from host chain to this chain. It also allows to prove and finalize withdrawals. This contract stores the following tokens: ETH.
Upgrade delay: No delay
Contains a list of proposed state roots which Proposers assert to be a result of block execution. Currently only the PROPOSER address can submit new state roots.
Upgrade delay: No delay
Sends messages from host chain to this chain, and relays messages back onto host chain. In the event that a message sent from host chain to this chain is rejected for exceeding this chain’s epoch gas limit, it can be resubmitted via this contract’s replay function.
Legacy contract used to manage a mapping of string names to addresses. Modern OP stack uses a different standard proxy system instead, but this contract is still necessary for backwards compatibility with several older contracts.
Value Locked is calculated based on these smart contracts and tokens:
Main entry point for users depositing ERC20 token that do not require custom gateway.
Upgrade delay: No delay
Main entry point for users depositing ETH.
Upgrade delay: No delay
The current deployment carries some associated risks:
Funds can be stolen if a contract receives a malicious code upgrade. There is no delay on code upgrades (CRITICAL).
