Written by: LINDABELL
At the recent Devcon conference, Ethereum Foundation core member Justin Drake proposed the Beam Chain proposal, planning to upgrade the Ethereum consensus layer through zkSNARK and zkVM technology to enhance the network's scalability, security, and efficiency. This vision has once again drawn attention to the importance of zkVM. As a general-purpose zero-knowledge virtual machine, zkVM can handle complex computations in a more flexible and efficient manner while freeing itself from dependence on traditional smart contract logic.
Driven by this trend, projects like RISC Zero, Succinct, and Cysic are seen as important participants in promoting innovation in this field. Among them, RISC Zero, with its zkVM based on the RISC-V architecture, has developed a series of open-source tools such as Zeth, Kailua, and Bonsai, which not only enhance block validation and Rollup performance but also provide technical support for Ethereum's ZK upgrade.
RISC zkVM ecosystem product matrix: from core technology to scenario applications
RISC Zero is a zkVM implementation based on the RISC-V instruction set architecture. As a general-purpose zero-knowledge computing platform, it supports various mainstream programming languages, such as Rust and C++, and can run almost any computational task. Compared to other zero-knowledge technology platforms, the prover and verifier of RISC Zero are fully open-source, allowing developers to generate and verify proofs locally. In addition, RISC Zero's verifier is compatible with various platforms, adapting to different blockchain ecosystems and simplifying the development process of decentralized applications.
In June this year, RISC Zero released zkVM 1.0. zkVM 1.0 not only supports multiple languages and complex computational tasks but also uses Continuations technology to break down large-scale computations into smaller segments, achieving efficient parallel computation and verification. According to the roadmap, RISC Zero plans to achieve a 20-fold improvement in zkVM performance and costs by the end of 2024, with optimizations including fully migrating the proof process to GPU (80% completed), introducing new RISC-V v2 circuit designs, and targeted optimizations for recursive circuits. At the same time, RISC Zero is integrating a series of acceleration modules for algorithms such as RSA, Keccak, and ECDSA to enhance the performance of Ethereum-related tasks and cryptographic operations.
Around the core capabilities of zkVM, RISC Zero has also developed a series of open-source tools and products. For example, through the Bonsai network, developers can generate zero-knowledge proofs without dedicated hardware; the Steel tool allows complex EVM computations to be offloaded to off-chain environments while keeping results verifiable, reducing on-chain execution costs; and Blobstream Zero provides more possibilities for data sharing and verification in modular blockchain ecosystems by bridging the Celestia data availability layer.
Zeth: Proving that the entire Ethereum block is constructed correctly
Zeth is an open-source Ethereum zero-knowledge block prover developed by RISC Zero based on its zkVM technology, capable of verifying the validity of Ethereum blocks through zero-knowledge proofs without relying on traditional validators or synchronization committees. RISC Zero defines Zeth as a Type-0 zkEVM, fully compatible with the Ethereum protocol and improving development efficiency through code reuse.
Ethereum co-founder Vitalik Buterin categorized zkEVM into four types in his article 'Different types of zk-EVMs', where Type-1 aims for complete and uncompromising equivalence to Ethereum; Type-2 focuses on being fully equivalent to EVM but not fully equivalent to Ethereum; Type-3 is almost equivalent to EVM; and Type-4 is completely incompatible with Ethereum.
Thanks to the high performance of RISC Zero zkVM, Zeth can complete the verification of Ethereum blocks in just a few minutes. Test data shows that Zeth can generate block proofs at a speed of 1.1 MHz and, by utilizing the 'continuations' feature, extend GPU clusters to boost the speed to between 4.7 MHz and 6.3 MHz. This performance optimization also reduces the cost of proof generation. According to tests, the proof generation cost for a block containing 182 transactions was only $21.72, with a cost of about $0.11 per transaction.
At the same time, during the development of Zeth, the RISC Zero team made full use of components from the Rust ecosystem, such as revm, ethers, and alloy, enabling developers to quickly implement block proof functionality and apply it to different scenarios. This design provides developers with more flexibility to adjust block construction logic as needed and adapt to future Ethereum improvement proposals.
At the application level, Zeth provides efficient solutions for zk Rollups, light clients, and cross-chain bridges. The construction of traditional zk Rollups and zkEVMs requires substantial time and funds, making it daunting for small teams. In contrast, Zeth, based on a modular zkVM architecture, allows developers to easily customize block validation logic. For example:
zk Rollup: Zeth can quickly realize block proof, shortening the development cycle of ZK Rollup and reducing capital investment.
Light client: Verifying block validity without rebuilding the block, reducing operating costs.
Cross-chain bridge: Zeth can verify the correctness of cross-chain data without leaking sensitive on-chain information through ZKP, reducing dependence on third-party trust and lowering the risk of cross-chain attacks.
In May this year, Zeth successfully expanded to support extracting Optimism block data from the Ethereum mainnet and generating ZKP to verify block correctness, also supporting on-chain verification. This means that with Zeth, Optimism can verify transactions more efficiently and resolve transaction disputes.
Bonsai: Allows developers to generate proofs without using their own hardware
Bonsai is a remote proof service designed specifically for zkVM applications, allowing developers to generate proofs without using their own hardware, thus solving the conflict between limited on-chain computing resources and high costs. Through Bonsai, developers only need to define the zkVM application to be executed and the input data, and Bonsai can run the computations in the background and generate the corresponding zero-knowledge proofs. This process requires no additional hardware deployment by the developers. Meanwhile, Bonsai utilizes a large number of GPU clusters to support the parallel processing of multiple computational tasks. In addition, Bonsai provides an easy-to-use API and SDK interface, making it easy for developers to integrate it into existing systems, further reducing development difficulties.
Based on this remote proof service, RISC Zero launched the open-source tool Bonsai Pay, combining OAuth2.0 identity authentication and ZKP technology, allowing users to send or receive tokens on the Ethereum network using their Google accounts. For example, when Alice wants to transfer funds to Bob, Alice can use Bonsai Pay to input Bob's Google email and the transfer amount. Bob can then log in to Bonsai Pay, enter his email address, and complete Google account authentication. Bonsai Pay will use OAuth 2.0 to generate an authorization token, proving that Bob is indeed the holder of that email. Subsequently, Bonsai Pay calls the Bonsai proof service to generate a zero-knowledge proof, demonstrating that Bob's Google account is associated with his wallet address. Once the smart contract verifies the proof, it will unlock the funds and transfer them to Bob's wallet address.
Throughout this process, Bonsai Pay verified the fact that 'Bob's Google account is associated with his wallet address' using ZKP technology while avoiding the disclosure of any specific information about the Google account.
Another important application of Bonsai is the Bonsai ZK co-processor (ZK Co-processor). It uses zero-knowledge proof technology to transfer complex computation tasks off-chain while generating tamper-proof proofs to ensure the correctness of results. Additionally, deploying the Bonsai co-processor is very straightforward; developers only need to write a zkVM application to handle logic and call Bonsai through a simple Solidity contract to run calculations and validate results. Throughout this process, the Bonsai proof service is responsible for generating the zero-knowledge proofs for off-chain computations, which can then be verified on-chain.
Bonsai ZK co-processor is suitable for on-chain applications requiring high performance and low cost. For example, in DAO governance, it can offload complex voting computations to off-chain, significantly reducing on-chain gas fees. The Bonsai DAO Governor has reduced the gas cost per vote by over 50% through the co-processor, effectively improving governance efficiency and lowering the participation threshold.
Boundless: A verifiable computation layer
In traditional blockchain architecture, to ensure the validity of transactions, all nodes need to repeat all computations of each transaction. This 'global re-execution' model, while ensuring security and consistency, also incurs extremely high computational costs. To address this issue, RISC Zero launched Boundless, allowing a single node to complete computations and generate a verifiable zero-knowledge proof, enabling other nodes to confirm results by simply verifying the proof without needing to repeat the computation.
Boundless simplifies the verification process through recursive composition technology. It merges multiple small zero-knowledge proofs into a single overall proof, allowing verifiers to check only one total proof instead of verifying all stage proofs one by one. To further optimize the efficiency of zero-knowledge proof generation, Boundless includes dedicated cryptographic acceleration circuits that enhance the efficiency of common tasks such as hash computation and digital signature verification.
Moreover, developers using Boundless do not need to have a deep understanding of zero-knowledge technology; they can simply write applications in familiar programming languages (such as Rust or Solidity). Currently, Boundless is open for free access to developers. They can utilize the proving service provided by Boundless to quickly build and deploy zero-knowledge applications on any blockchain without migrating existing systems or updating verification contracts.
Blobstream Zero: A zkVM cross-chain bridge simplifying cross-chain data verification
Blobstream Zero is a zkVM-based cross-chain bridge launched in collaboration between RISC Zero and Celestia, aiming to seamlessly connect Celestia's data availability layer to existing modular blockchain ecosystems. By sharing and verifying data on Celestia, Blobstream Zero facilitates more convenient data transfer and verification between chains.
As a fully open-source public product, Blobstream Zero allows any project or developer to run local instances and generate zero-knowledge proofs. Additionally, Blobstream Zero can support ZK co-processors. ZK co-processors are essentially off-chain computation tools that require reliable data to perform computations. Blobstream Zero can obtain data from blockchains such as Celestia and can prove that the transmitted data is reliable by generating ZK proofs.
Steel: A new paradigm for off-chain execution and on-chain verification of smart contracts
Steel is an open-source tool launched by RISC Zero that uses zkVM technology to achieve off-chain verifiable smart contract execution. Through Steel, developers can offload EVM operations from on-chain to off-chain execution while generating zero-knowledge proofs, ensuring the authenticity and verifiability of computation results.
Traditional smart contracts require complete on-chain execution of all logic, which not only incurs high gas costs but also limits the development of complex applications. The off-chain computation and on-chain verification mechanism of Steel addresses this problem. For example, in a simple smart contract that checks if a certain account's ERC20 balance is greater than 1 and increments a counter variable, the traditional method requires complete on-chain execution of the logic, while Steel completes the computation off-chain and generates a zero-knowledge proof, requiring only the verification of the proof on-chain without having to repeat the contract logic.
Currently, RISC Zero has released Steel 1.0, and partners have already used this tool to develop applications. For example, in a contract call processing about 400,000 SLOAD operations, through Steel, computations were offloaded to off-chain execution, and the generated zero-knowledge proof was then validated on-chain. The proof generation cost was less than $10, and the on-chain verification cost was below 300,000 gas.
Kailua: A hybrid ZK solution driving Rollup architecture innovation
After the release of Zeth, RISC Zero launched Kailua, aiming to provide a hybrid ZK Rollup upgrade solution for optimistic Rollups. Traditional optimistic Rollups typically require a 7-day challenge period, resulting in slow transaction finality, while ZK Rollups can achieve finality quickly but incur high costs for continuously generating zero-knowledge proofs. Kailua combines the advantages of both, achieving a balance between cost and efficiency through a hybrid architecture. As an extension of the Optimism Kona framework, Kailua not only supports unmodified Kona running on zkVM but also introduces an innovative dispute resolution mechanism that lowers staking requirements and reduces finality delays, thereby improving system efficiency and usability.
In the architecture of Kailua, the dispute mechanism adopts a brand-new design. First, its dispute resolution mechanism removes time limits, allowing verifiers ample time to generate proofs when encountering special situations such as network interruptions, thereby enhancing system resilience. Even in extreme cases, RISC Zero zkVM's scalable architecture can complete proofs within an hour. Moreover, Kailua's on-demand verification feature allows developers to flexibly configure verification frequency, enabling a gradual transition to a fully verified Rollup model at lower costs.
Unlike ZK Rollup, Kailua's design does not require continuous proof generation. For low-frequency empty blocks or Rollups with special contract requirements, Kailua offers a more cost-effective option. At the same time, Kailua significantly reduces the staking cost requirements for Rollups. The staking amount for traditional optimistic Rollups increases linearly with longer finality periods, while Kailua's optimized design fixes the staking requirement, allowing the system to maintain security and activity at lower costs even over long periods.
Currently, Kailua is fully open-source. Developers can use its command-line tools to deploy a local Optimism test network and quickly upgrade to a network that supports ZK fault proofs. Kailua also supports simulating fault proposals, helping developers understand how verifiers challenge erroneous states through zkVM, thus gaining deeper insights into its dispute resolution mechanisms. In the future, Kailua will further optimize costs and performance and expand support for more Rollup frameworks.
Summary
As can be seen from the above, RISC Zero's zkVM product matrix is promoting the development of zero-knowledge proof technology in multiple fields. Zeth and Kailua focus on Rollup architecture optimization, improving block validation efficiency and dispute resolution speed. Bonsai provides remote proof services, reducing hardware dependence and operational costs, allowing developers to build applications more efficiently. Meanwhile, Blobstream Zero offers reliable support for modular blockchain ecosystems through efficient verification of cross-chain data. Furthermore, Steel reduces gas costs for executing smart contracts through its off-chain computation and on-chain verification model.
Of course, while continuously improving the zkVM product matrix, RISC Zero is also actively promoting innovation in the underlying technology of zkVM. Recently, RISC Zero zkVM released version 1.2, introducing a new pre-compilation method that allows developers to deploy pre-compilation logic alongside applications without having to embed it in the zkVM itself. This means developers can add new pre-compilation logic without modifying on-chain verification contracts or coordinating the configuration of provers, and without needing to fork or make major changes to the zkVM to achieve performance optimization. Moreover, by defining pre-compilation through applications, it can also reduce the computational costs of proof generation. For example, after Automata integrated RSA pre-compilation, the execution cycle was reduced from 39 million to 217,000, with costs decreased by about 180 times.
With the continuous optimization of zkVM technology, its development potential will gradually be reflected in multiple application scenarios. However, to better unleash this potential, it still relies on ecological collaboration and the actual performance of technology implementation.
