The Optimism page of Bitcoin Layers is under development.

Bitcoin Layers' focuses its efforts on reviewing protocols that claim to be a bitcoin layer and BTC wrappers that live on alternative chains. Alternative network provide a snapshot into the network architecture, but largely focus on review related to BTC wrappers on the network. If the network is an Ethereum L2, we recommend heading to L2Beat for a deeper dive into the architecture.

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Optimism

Overview

Status

Mainnet

Type

Alt. Rollup

Fee Token

ETH

BTC Supply

₿0

Optimism is an Ethereum rollup that that supports a variety of wrapped BTC tokens.

CUSTODY

DATA AVAILABILITY

OPERATORS

FINALITY ASSURANCE

Risk Summary

Bridge contracts are upgradeable

A centralized party can immediately upgrade specific system contracts. This risk may be relevant to BTC-backed tokens locked in the layer's official bridge contract.

All BTC pegs have custodian trust assumptions

All BTC backing wrapped tokens on this network are ultimately secured by custodians. Users trust that these custodians will not misappropriate funds and keep their assets pegged 1:1. Each custodian has their own risks. Learn more in the trust assumptions review section.

Another data availability layer is used

Data related to the network's state is made available by another consensus network. The network's state cannot make progress if the data availability layer withholds the data. If the network cannot make progress, user funds can be frozen.

A centralized entity is the network operator

The network is operated by a centralized operator. If this operator goes offline, the network can be halted which can freeze user funds. Please see the trust assumptions to learn if their is a fallback mechanism for liveness failures.

Trust Assumption Review

BTC Custody

High

🚨

Users trust the Threshold Network to keep tBTC backed and a 9 member federation to manage tBTC's bridge between Base and Ethereum

tBTC's peg with bitcoin is managed by the Threshold Network, a distributed but permissioned two-way peg. tBTC is minted on Ethereum and then bridged to the network via a custom bridge implementation.

This bridge is managed by a 6/9 federation. Bitcoin users trust that 6 of the 9 members of this federation do not collude and steal user funds.

Learn more about Threshold tBTC's custody model→

Data Availability

Medium

⚠️

Data is stored and made available by Ethereum full nodes

The data for network's state is made available by Ethereum full nodes. Anyone can run an Ethereum node and verify the state of the network.

Network Operators

Medium

⚠️

Optimism blocks are produced and proposed by a centralized operator, but users can propose their own state updates in the event of censorship or liveness failures

The network's sequencer is managed by one entity. The sequencer can censor transactions and can also cause liveness failures if it goes down. Users can bypass the sequencer and send their transactions directly to its parent chain. Users can also self-propose their own state transition, and exit the network to its parent chain.

Finality Guarantees

High

🚨

Optimism state transitions finalize on Ethereum. Rollup nodes finalize after applying the STF over data blogs. Light clients finalize after a fraud proof window passes

The network's state is updated offchain by nodes who apply state transition logic over the data made available by its data availability layer. After a new state is generated, a state root is posted to bridge programs.

If a proposer were to publish a malicious state update, they could be challenged via fault proofs. Anyone with sufficient capital resources can submit a fault proof.

Further sections under review

Aspects related to bitcoin security, relevant technologies, and some two-way pegs have not been reviewed.

They will be reviewed by our team soon.