What is Opside
The 3-layer architecture
Opside proposes a 3-layer blockchain architecture, where layer 2 is an EVM-compatible and rollup-friendly chain, and layer 3 is composed of multiple zk-rollups. The chain makes many system-level optimizations for zk-rollups and introduces the concept of native rollup. Based on this architecture, layer 2 gains asset variety from bridges and infinite scalability from rollups, providing a more friendly running environment for applications.
Layer 1: zk-bridge
Opside has a zk-bridge between layer-1 public blockchains (like Ethereum and BNB chain) and layer-2 Opside chain. The zk-bridge supports secure and trustless asset transfers between layer 1 and layer 2.
The short-term solution for zk-bridge is to use on-chain oracle and off-chain zk state validity proofs, which double-check the correctness of the cross-chain state with high security. Its security assumption is similar to LayerZero, which is widely accepted by the market. But in the long run, we will use zk state validity proofs combined with zk consensus proofs to implement the trustless zk-bridge completely.
There is also a liquidity bridge to support faster and cheaper asset transfers between the Opside chain and more layer-1 blockchains. The liquidity bridge leverages token vaults on different blockchains to support cross-chain token exchanges at varying prices, providing better liquidity to assets on layer 2.
Layer 2: a rollup-friendly chain
Layer 2 is an EVM-compatible blockchain (called Opside chain) with optimizations to zk-rollups. We propose the idea of native rollups, which utilize rollup slots (some precompiled smart contracts) to integrate zk-rollups into the blockchain consensus.
Therefore, the Opside chain's consensus is a hybrid of PoS and PoW:
PoS. Users first stake their tokens to be validators on layer 2. Then they are able to generate blocks to earn layer-2 block and gas rewards.
PoW. Validators with computing power can generate batches and proofs for layer-3 zk-rollups and send them to layer 2. Then they get layer-3 batch and gas rewards.
In this way, the consensus incentivizes miners to provide the computing power needed by zk-rollups, which will attract a bunch of hardware to join the network.
Besides the computing power, the rollup slots can give native rollups more support, like cross-rollup communication and zkp verification acceleration. All these will finally improve the performance and functionality of zk-rollups.
Layer 3: rollup as a service
On layer 3, zk-rollups will provide standalone, high-TPS, and low-gas execution environments to applications. They are suitable for high-throughput web3 applications like order book DEX, games, and social networks. Developers can run their applications on pre-deployed general-purpose rollups or launch their own application-specific rollups on rollup slots (with some economic models). Then applications are running fully on-chain without the concern about servers.
To support different zkEVMs running on layer 3 in a decentralized manner, we designed a decentralized zk-rollup consensus named PoVP (Proof-of-Validity-Proof). It allows anyone with computing power to compete for the next batch and proof of a zk-rollup. The process is absolutely trustless and permissionless.
Advantages
High security. With zk-bridge, layer-2 Opside chain securely connects to layer 1. Then layer-3 zk-rollups inherit the security of layer 2. So the Opside 3-layer architecture has a high security level guarded by zero-knowledge proofs.
Infinite scalability. The entire system can be scaled infinitely by adding an arbitrary number of rollups to layer 3. Users can use pre-deployed general-purpose rollups or launch their own application-specific rollups.
Asset variety. By building bridges to multiple layer-1 blockchains, layer 2 and 3 can accept various assets from layer 1. Liquidity bridge is faster and cheaper, while zk-bridge is more secure, especially for large-amount transfers.
Use cases
A typical use case is to deploy games to layer 3 and use layer 2 as a marketplace for trading game items. In this way, players play different games in different rollups without a throughput burden to each other as well as to layer 2. Then they transfer game items to layer 2 for trading, in a DEX or an NFT marketplace. Assets bridged from layer 1 can also participate in the trading. For example, players can sell game items to ETH or use ETH to buy these items.
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