Marathon announced yesterday their layer two Anduro proposal. While there aren't really any fundamentally new parts or developments in Anduro's design, they are composed slightly differently compared to other existing sidechain systems such as RSK or Liquid/Elements.
Anduro is a federated model that uses a quorum, called “Collective” in published documents. The main distinction between Anduro and other sidechain proposals is the explicit design based on collective operation and the ability to create and manage multiple sidechains with different architectures. This is not that different from the concept of transmission chains allowing for a larger network of side chains, rather than a single network.
Anduro will also be merge-operated, which like RSK (also using a federated peg), does not provide any type of additional security for bitcoin tied to the sidechain owned by the federation. However, like RSK, it provides POW security to other assets that might be issued on the sidechain, not attached to the main chain and held by the federation.
Peg and Consensus Model
The actual link between the main chain and the side chain is fundamentally the same as that of Liquid and, in detail, appears to be roughly identical in terms of structure and implementation. The collective will launch with 15 members as officials, the entities that actually manage the multisig keys involved in peg management, and 50 or more contributors, who appear to be similar to Liquid's partial members who can whitelist and initiate withdrawals from the sidechain(s). ), even if they do not actively participate in processing these withdrawals.
Much like Liquid, Anduro will also use a formal organization to manage governance matters. That is, managing network upgrades, deciding on future changes in the composition of the federation's members and, in general, any problems that arise regarding the operation of the sidechains managed by the collective. The security of the federation ultimately relies on jurisdictional diversity in order to maintain any type of resistance to censorship or security against confiscation of funds, even if a federation is made up of honest members.
The interesting part of the design here is that, unlike RSK, the collective plays an active role in the consensus process beyond facilitating the operations of the fixation mechanism. In Anduro, the collective actually reaches consensus on block content for the sidechain via a Byztanine Fault Tolerant (BFT) algorithm or round-robin selection where only one member builds the blocks for that round. They also periodically sign blocks to function as a checkpoint system to prevent any reorganization of anything in the historical past. Once signed and verified, miners are unable to reorganize sidechain blocks without help from the collective.
These two factors essentially function as a firewall between miners' extractable value opportunities and miners. MEV is any opportunity available to miners where reordering transactions, such as initial orders on a decentralized exchange, may present an opportunity for that miner to earn additional revenue when mining their next block. MEV has shown a tendency to increase centralization pressures for block producers in other networks in which it has become prevalent. Since the collective actually decides the content of sidechain blocks and miners simply commit to them with proof of work, the collective acts as a shield against centralizing pressures on block producers (in the case of Bitcoin miners) by taking on the role of real block construction.
In the long term, Marathon says it intends to work towards establishing trustless fixation and consensus mechanisms, specifically citing BitVM as an example of how this could be achieved. While this calls into question the ability to maintain the MEV protections that the current architecture has in such a transition, it currently prevents MEV from posing a risk of centralization pressures for miners. It is also important to note that BitVM, ultimately, as designed with a provider-verifier model, inherently requires defined participants to manage all funds locked into a BitVM peg. While this radically improves the home security model by allowing provable penalization of dishonest participants by a single member, massive changes to the design of BitVM itself would be required to completely remove the need for the equivalent of a federation .
Overall, the architecture strikes a good balance between implementing a variation of existing sidechain designs, while intentionally creating in its current iteration a sort of layers of protection between sidechains and miners in terms of concerns the risks of VPD.
The first two
At launch, Anduro will support two sidechain architectures, one based on Bitcoin, the other on Ethereum.
Coordinate: Coordinate is the variant of the Bitcoin sidechain. It will implement small changes in Bitcoin, including native support for asset issuance similar to Liquid, and intends to address use cases for ordinals and tokens such as BRC-20 , as well as the primitive DeFi products and services that have grown around them.
Alys: Alys is the variant of the Ethereum sidechain, essentially just porting the Ethereum virtual machine and Solidity onto a Bitcoin sidechain. The hope is that it can provide a new learning curve environment allowing Ethereum application developers to focus on building services and tools on top of Bitcoin.