We’re excited to announce Spire, one of the first zk rollups to be integrated with Espresso’s shared sequencer. Spire is a modular L3 network built on top of zkEVM L2s, scaling Ethereum in a fractal fashion.

What is Spire?

Spire provides the infrastructure for a broad set of developers to spin up their own appchain L3s that are interoperable with one another. So Spire is a type of Rollup-as-a-service(RaaS), and also a L3-as-a-service.

Unlike other Raas, Spire focuses on L3 on top zkEVMs. Through its recursive zkrollup architecture, L3s spun up with Spire can scale vertically and are also equipped with a special power that taps into contracts on L2s such as Scroll.

In addition, Spire itself will introduce its own L3 that empowers other appchains on Spire.

Why L3?

There are many design spaces in rollups and we are excited for these approaches. Among them, here are some reasons why Spire is taking a path toward L3s or fractal scaling on zkEVMs.

We expect the majority of onchain activity to happen on L2s in the short term, so there will be deep liquidity, advanced smart contracts, and useful protocols on L2s in the future. (Especially on zk rollups in the long term, because of the fast finality and therefore better composability and interoperability).

The Spire architecture allows app-specific L3s to tap into these smart contracts on L2s. For example, users on a gaming L3 can sell their in-game currency for ETH by tapping into an Uniswap liquidity on L2s like Scroll. In other words, L3s are able to leverage L2 resources and benefit from EVM network effects.

Furthermore, as Vitalik wrote in his post “What kind of layer 3s make sense?”, L3s can serve customized functionality + customized scaling. More specifically, as has been covered by StarkWare who first advocates fractal scaling, the benefits of L3s include:

• Hyper scalability

• Greater control by app developers

• Functioning as a test network for L2s (similar to Kusama for Polkadot)

• Privacy

In our view, this enhanced control is an underrated advantage. App developers with Spire can design appchains where the first few transactions are free for their users.

Also, they will be able to monetize based on the transaction fee generated + MEV, even without issuing tokens. Or their tokens will be able to capture the value based on the transaction fee if app developers decide to issue tokens. App developers can also design appchains in a way that transaction fees could go to a referrer user. We are currently exploring fee and MEV distribution mechanisms with the Espresso team to open up a new economy.

zkVM, not zkEVM

Spire has also a powerful execution environment utilizing RISC Zero. This is zkVM, not zkEVM.

Web3 developers, such as solidity developers, represent a very small number of all developers worldwide. Electric Capital Developer Report (page 112) indicates that web3 developers are approximately 0.07% of all developers.

By leveraging RISC Zero, Spire supports smart contracts written in WASM, enabling the developers to write contracts in any languages that compile down to WASM, such as Rust, Go, and C++. We believe that this infrastructure is important for crypto to reach a broader set of developers and to go beyond the limitations of EVM.

With this execution environment, more developers, including non-crypto developers today, will hack more casually and easily on a decentralized tech stack. We will see more innovation in a world where 10,000 apps are built in a week compared to a world where only 10 apps are built in a week.

Also this doesn’t mean that we ignore EVM and its network effects. In fact, RiscZero + Spire will be able to support EVM inside its zkVM. Not only that, L3 appchains spun up with Spire are able to tap into EVM contracts underlying L2s too.

Why Espresso’s Sequencer?

Today’s rollups rely on centralized sequencers. This means that a user’s transaction could be censored and selectively blocked. Espresso’s shared sequencers can mitigate the centralization and rollups can set transaction ordering to be executed in a decentralized way.

Moreover, by leveraging Espresso’s shared sequencer, rollups can achieve native interoperability with one another. The remarkable feature of Espresso’s sequencer is its capability to enable atomic cross-rollup composability. This means that developers can define that a transaction on Rollup A can be included in a block only if a different transaction on Rollup B is included within the same block. For example, a DeFi rollup can send assets to a gaming rollup only when a player successfully completes a challenge within the game, without trusting a third party.

We continue to work with the Espresso team and design the best ways, such as transaction bundles signed in the sequencer network, in order to leverage the full potential and capabilities of this modular infrastructure.

Data Availability and Restaking

In addition to sequencers, rollups comprise multiple components that work together to enable their functionality. One critical component is the data availability layer (or DA layer). Espresso has developed its own DA layer, which is secured by its ‘HotShot’ consensus.

Spire uses this DA layer and will also gain security through restaking, a mechanism that borrows security from Ethereum validators. For more information on this, Espresso recently announced a collaboration with EigenLayer.

Stay in touch with us

Spire plans on releasing a public testnet in 2024, please get in touch with us and follow our updates on Twitter.

If you are a developer or researcher and are interested in contributing to Spire and the modular movement, please reach out to us.

• Twitter: https://twitter.com/Spire_Labs

• Website: https://www.spire.dev/