Original author: Frank, PANews
On April 10th, a16z Crypto released a zkEVM solution called Jolt, aiming to accelerate and simplify blockchain expansion operations. Jolt integrates SNARK zero-knowledge proof, providing a framework for EVM-compatible Rollups, which can help developers create SNARK-based L2 solutions. The team stated that Jolt's speed is "twice as fast" compared to the current zkVM.
As the technical principles of Jolt are relatively complex, here is a brief explanation of several technical terms that may be involved:
zkSNARK is a powerful zero-knowledge proof primitive and the basis for building zkVM and zkEVM.
zkVM is a general zero-knowledge virtual machine concept that supports any instruction set.
zkEVM is a specific instance of zkVM, specifically designed to be compatible with EVM.
ZK Rollup uses zkVM or zkEVM to enhance the scalability of Ethereum while also considering privacy.
What is Jolt?
Jolt is a new type of SNARK solution that provides a more concise and efficient way to build zkVM (zero-knowledge virtual machine). In fact, as early as August 2023, a16z crypto proposed concepts related to Lasso and Jolt. In the context of the slow and costly nature of SNARK technology, these two technologies were proposed.
Lasso is a new lookup parameter that can significantly reduce the cost for provers; Jolt, using Lasso, provides a new framework for designing SNARK for so-called zkVM and a broader front end. Together, they improve the performance, developer experience, and verifiability of SNARK design, thereby enhancing construction in web3. This further promotes the use of zero-knowledge proofs in the blockchain field.
Before understanding Jolt, it may be necessary to first understand zkVM and zkEVM.
zkVM is a general concept referring to a zero-knowledge virtual machine. Similar to zkEVM, zkVM allows programs to be written in high-level languages such as C++ or Rust, and then the virtual machine compiles the program into some form of intermediate representation (such as circuits or arithmetic constraints), which is then proven by proof systems like zkSNARK. Unlike zkEVM, zkVM is not limited to EVM compatibility but supports any instruction set. Jolt is a high-performance zkVM implementation for the RISC-V instruction set.
We can think of zkVM as a special "black box" that can prove to the outside world, while protecting privacy, that it has indeed executed the calculation according to the predetermined program. However, traditional zkVM requires a lot of tedious computation in the process of generating this proof, resulting in very low performance.
The core innovation of Jolt is to find a more efficient mathematical method to generate this proof:
First, Jolt cleverly transforms the calculation to be proven into a special type of polynomial, which we may call the "calculation polynomial." The characteristic of this polynomial is that its value is zero only when the black box has indeed correctly executed the calculation.
To prove that the value of the "calculation polynomial" is zero, Jolt uses an interactive protocol called "sumcheck." This protocol can make the verifier believe in a short amount of time that the polynomial value is zero, without actually computing the entire polynomial. This is somewhat similar to a teacher being able to judge the correctness of an entire exam paper by checking only a few questions.
Technical Advantages of Jolt
The technical principles of Jolt are very complex, but simply put, in the process of blockchain network development, zkVM is a key technology in improving the scalability of blockchain networks, providing effective proof while ensuring privacy. Vitalik, in his recent keynote speech at the Hong Kong Web3 Carnival, made a detailed discussion around zkSNARK technology. Vitalik stated, "Finding ZKSNARKS is very useful in terms of privacy and scalability."
However, the speed of proof generation and computational costs have always been a major challenge for practical application of zkSNARK technology, and have been a focus of academic and industry research in recent years. Traditional zkSNARK solutions, such as Pinocchio and Groth16, may take several hours or even days to generate proofs for complex computations, and require a large amount of memory and storage resources. This performance bottleneck severely restricts the application of zkSNARK in many practical scenarios.
If blockchain is to achieve large-scale applications and real-time verification, improving the performance of zkSNARK is crucial.
According to a16z Crypto, the initial Jolt implementation is approximately 6 times faster than RISC Zero on a CPU, 2 times faster than the recently released SP1, and is expected to increase the speed of Jolt by about 1.5 times in the coming weeks.
Jolt's current speed is already more than 2 times faster than existing zkVM, but there is still a lot of room for optimization.
Jolt also cleverly utilizes certain algebraic properties of polynomials to achieve a more efficient polynomial commitment scheme. This further reduces the size of the proof and verification time.
Potential Changes Brought by Jolt
From an engineering perspective, Jolt adopts a series of optimization methods, such as more compact circuit design, more efficient pipelining, and more extensive parallelization, to maximize the hardware's computing power.
Suppose you are a Web3 developer and want to deploy a blockchain-based poker game on Ethereum. This game requires on-chain shuffling, dealing, and comparing card values, and each operation needs to be implemented for privacy protection and verifiability using zkVM circuits.
If you use existing zkVM solutions such as ZoKrates or bellman to build such a circuit, it may take several hours or even days. Because the current performance of zkVM is still relatively low, generating zero-knowledge proofs for complex circuits requires a significant amount of computing resources and time. This means that the development and testing cycle will be very long.
However, if you use Jolt to build the same circuit, the situation will change significantly. According to the Jolt team's testing, the current Jolt implementation is 2-5 times faster than mainstream zkVM solutions. This means that if it originally took 10 hours to generate a proof, it may now only take 2-5 hours.
Overall, the 2-5 times performance improvement brought by Jolt means that the usability and ease of use of zkVM technology have been significantly improved. This will significantly lower the threshold for Web3 developers, shorten the development cycle of applications, and provide a better user experience for end users. In the longer term, Jolt is expected to accelerate the large-scale application of zkVM technology, allowing more privacy protection and verifiable computing capabilities to benefit every Web3 user.
Of course, Jolt is still in the early stages of development, and the 2-5 times performance improvement is just the beginning. With the continuous iteration and optimization of Jolt technology, the performance of zkVM will be further improved, ultimately paving the way for the large-scale application of Web3.
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