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In its initial version, the Logos Blockchain is intended to support Sovereign Zones - the most customisable, performant solutions for applications built on Logos. Sovereign Zones have broad freedom to define their own state, using the Logos Blockchain to ensure consensus and the availability of Zone data. At the same time, Sovereign Zones have the option to take advantage of some interoperability features provided by Bedrock - including bridging and cross-Zone messaging.
This design allows applications built on Sovereign Zones to have low fees and maximum scalability. While the Logos Blockchain is designed to eventually support permissionless and fully interoperable Native Zones with minimal setup required, this support remains a work in progress and is slated for inclusion in later versions of the protocol.
The idea behind Sovereign Zones is to make performant applications with the freedom to define an execution environment to suit their needs, with the Logos Blockchain providing economic security and data availability guarantees that the Zone alone could not provide, helping to bootstrap Zones’ economic security. To ensure the correctness of the Zone state, Sovereign Zones are left to their own devices instead of relying on a smart contract on the L1 as with Ethereum L2s. This could be done in any number of ways - including publishing ZK validity proofs to be verified by its validators, providing a challenge window for fraud proofs, or by requiring Zone nodes to re-execute the state transition function.
Bedrock does not attempt to interpret Sovereign Zone data, instead providing operations via Mantle to allow Zones to inscribe their state updates permanently to the blockchain. In future versions of the protocol, Sovereign Zones will also be able to post data temporarily in the form of a LogosDA blob, which is distributed among DA nodes with blob commitments written on-chain. This model will allow all Logos Light Nodes to easily verify the availability of Zone data while ensuring that the Zone state enjoys the benefits of Cryptarchia consensus.
One example of a Sovereign Zone that uses validity proofs to verify its state and LogosDA to verify the availability of its data.
The Sovereign Zone depicted above has a single sequencer that processes transactions from clients and sends the batched state data to LogosDA, while simultaneously creating ZK proofs for its state updates and distributing them off-chain. Zone light nodes can then verify the proofs received from the sequencer and check the availability of the data via data availability sampling.
The Sovereign Zone model described above is very similar to that of conventional Sovereign Rollups. In fact, Sovereign Zones can be built as pure Sovereign Rollups, with Bedrock only used for ordering and data availability guarantees. However, Bedrock also provides some optional functionality that somewhat increases the decentralisation and interoperability of Sovereign Zones without significantly compromising the benefits of the Sovereign Rollup design.
While a Sovereign Zone can be implemented with just one sequencer to update the Zone state, this design allows the sequencer to take full advantage of any MEV and represents a centralised point of failure. On Logos, it is also possible to distribute sequencing rights to a permissioned set of parties who take turns sequencing the Zone according to a round-robin schedule. This model provides more Bedrock-level protections for Sovereign Zone users, including an automated timeout for unresponsive sequencers. It also allows a given threshold of sequencers to update the sequencer list to remove a malicious sequencer. All these operations are handled by Mantle channels.
Users can also take advantage of built-in token bridging to transfer value between Bedrock and Sovereign Zones. A Zone’s associated Mantle channel maintains a token balance, which keeps track of the total token value stored in the Zone. This balance is updated as value is deposited to or withdrawn from a Zone, with notes of equivalent value destroyed or created on Bedrock as a result of these operations.
Note that, unlike the Native Zone design, Sovereign Zones do not maintain a Common Ledger of UTXO notes. It is the Sovereign Zone’s responsibility to ensure that token transfers are executed correctly within its own state. Bedrock only ensures that the total token value withdrawn from a Sovereign Zone does not exceed the value deposited.
Sovereign Zone sequencers can use Mantle channels to submit messages with arbitrary data, allowing them to communicate on-chain with other sequencers. Sequencers can use these messages to coordinate actions with other sequencers of the same Zone, for example to agree to sign a message modifying the sequencer list. They can also be used to arrange action across several Zones, such as atomic token transfers or other coordinated state transitions. In the latter case, sequencers must interpret all new messages and determine whether the message is directed to them. The Logos Blockchain provides a suggested message standard to make it easier for sequencers to interpret messages from other Zones, but anybody can define their own standard if they so desire.
Sovereign Zones can implement almost anything, ranging from applications to virtual machines that are home to many different applications. They are best suited for applications that require high performance and do not need strong interoperability.
The Logos Execution Zone is a prime example of a Sovereign Zone on the Logos Blockchain. It serves as the home for applications built using the complete Logos stack, including its messaging and storage modules. It also provides support for private accounts and program execution, with the state being verified via zero knowledge proofs. For more information about the Logos Execution Zone, see here.