What changes will a16z Crypto's latest zkVM solution Jolt bring?

Author: Frank, PANews

On April 10, a16z Crypto released a zkEVM solution called Jolt, aimed at accelerating and simplifying blockchain scaling operations. Jolt integrates SNARK zero-knowledge proofs and provides a framework for EVM-compatible Rollups, helping developers create SNARK-based L2 solutions. The team stated that Jolt is "twice as fast" compared to current zkVMs.

Due to the complex technical principles of Jolt, here is a brief explanation of several technical terms that may be involved:

zkSNARK is a powerful zero-knowledge proof primitive that forms the basis for building zkVM and zkEVM.

zkVM is a general concept of a zero-knowledge virtual machine that supports arbitrary instruction sets.

zkEVM is a special case of zkVM, specifically designed to be EVM-compatible.

ZK Rollup uses zkVM or zkEVM to enhance Ethereum's scalability while maintaining privacy.

What is Jolt?

Jolt is a new type of SNARK solution that offers 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. These two technologies were introduced against the backdrop of slow and costly SNARK technology.

Lasso is a new lookup parameter that can significantly reduce the prover's cost; Jolt, using Lasso, provides a new framework for designing SNARKs for the so-called zkVM and broader front-end applications. Together, they enhance the performance, developer experience, and auditability of SNARK designs, thereby improving construction in web3 and increasing 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 like C++ or Rust, which the virtual machine then compiles into some intermediate representation (such as circuits or arithmetic constraints) and proves the execution process of the intermediate representation using proof systems like zkSNARK. Unlike zkEVM, zkVM is not limited to EVM compatibility but supports arbitrary instruction sets. Jolt is a high-performance zkVM implementation targeting the RISC-V instruction set.

We can think of zkVM as a special "black box" that can prove to the outside world that it has indeed executed computations according to a predetermined program while protecting privacy. However, traditional zkVMs require a lot of cumbersome calculations to generate this proof, resulting in very low performance.

The core innovation of Jolt is finding a more efficient mathematical method to generate this proof:

First, Jolt cleverly transforms the computation to be proven into a special polynomial, which we may call the "computation polynomial." The characteristic of this polynomial is that its value will only equal zero if the black box has indeed executed the computation correctly.

To prove that the value of the "computation polynomial" equals zero, Jolt uses an interactive protocol called "sumcheck." This protocol allows the verifier to be convinced that the polynomial's value is zero in a shorter time without needing to actually compute the entire polynomial. This is somewhat similar to a teacher checking only a few questions from a student's exam to determine if the entire paper is correct.

Technical Advantages of Jolt

The technical principles of Jolt are very complex, but simply put, in the development of blockchain networks, zkVM is a key technology for enhancing the scalability of blockchain networks, providing effective proofs while ensuring privacy. Vitalik recently elaborated on zkSNARK technology in his keynote speech at the Hong Kong Web3 Carnival. Vitalik stated, "Finding ZKSNARKS is very useful for privacy and also very useful for scalability."

However, the speed of proof generation and computational overhead has always been a major challenge for the practical application of zkSNARK technology, and it has been a focus of research in both academia and industry in recent years. Traditional zkSNARK solutions, such as Pinocchio and Groth16, can take several hours or even days to generate proofs for relatively complex computational logic, consuming a large amount of memory and storage resources. This performance bottleneck severely limits the application of zkSNARK in many practical scenarios.

If blockchain is to achieve large-scale applications and real-time verification, enhancing zkSNARK performance is a crucial step.

Specifically, the proof generation process of zkSNARK involves complex cryptographic algorithms, such as elliptic curve pairing and polynomial interpolation, which consume significant computational resources. Especially when the scale of the computation circuit being proven is large, the computational complexity of proof generation can increase exponentially.

According to a16z Crypto, the initial Jolt implementation is approximately 6 times faster than RISC Zero on CPU and 2 times faster than the recently released SP1, with plans to increase Jolt's speed by about 1.5 times in the coming weeks.

Jolt's current speed is already more than twice that of existing zkVMs, but there is still significant 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 the time required for verification.

Potential Changes Brought by Jolt

From an engineering perspective, Jolt employs a series of optimization techniques, such as more compact circuit designs, more efficient pipelining, and greater parallelization, to maximize the computational power of the hardware.

Suppose you are a Web3 developer looking to deploy an on-chain poker game on Ethereum. This game requires shuffling, dealing, and comparing cards on-chain, with each operation needing to be implemented through zkVM circuits for privacy protection and verifiability.

If you use existing zkVM solutions like ZoKrates or bellman, building such a circuit could take several hours or even days. This is because the current zkVM performance is still relatively low, and generating zero-knowledge proofs for complex circuits requires a lot of computational resources and time overhead. This means that the development and testing cycles would be very lengthy.

However, if you use Jolt to build the same circuit, the situation would change significantly. According to tests by the Jolt team, the current Jolt implementation generates proofs 2-5 times faster than mainstream zkVM solutions. This means that if generating a proof originally took 10 hours, it might 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 enhanced. This will greatly lower the barrier for Web3 developers, shorten application development cycles, and provide end users with a better experience. 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 continuous iteration and optimization of Jolt technology, the performance of zkVM will further break through, ultimately paving the way for the large-scale application of Web3.