Deciphering Zero-Knowledge Proofs: A Comparative Study of zkVMs and zkEVMs
zkVMs: The Flexible Approach
zkVMs, or zero-knowledge virtual machines, are essentially VMs implemented as circuits for a zero-knowledge proof system. This means that instead of proving the execution of a program, you’re proving the execution of a VM. This approach is often likened to the CPU approach in computing.
The instructions of the actual program can be passed as public input to the circuit, allowing everyone to see what program is being proven. There are several zkVMs available, including Cairo (used by Starknet), Miden (a project from Polygon), and Risczero (a project aiming to support the set of RISC-V instructions). However, each of these supports a different instruction set, meaning they are not compatible with each other.
zkEVMs: The Compatible Approach
On the other hand, we have zkEVMs, which are EVM-compatible virtual machines that support zero-knowledge-proof computation. Unlike regular VMs, a zkEVM proves the correctness of program execution, including the validity of inputs and outputs used in the operation. The primary aim of a zkEVM is to support the Ethereum VM, making it a more familiar environment for developers already working with Ethereum.
The Trade-offs
When it comes to choosing between zkVMs and zkEVMs, it’s important to understand the trade-offs. zkVMs offer flexibility, allowing for a distinct set of fundamental trade-offs and foundational parameters. This can be advantageous for certain applications.
zkEVMs, however, aim to maintain compatibility with the Ethereum Virtual Machine (EVM). This can be beneficial for developers already familiar with the EVM environment. But this compatibility might come with trade-offs in terms of performance and flexibility.
In conclusion, both zkVMs and zkEVMs have their unique advantages and trade-offs. The choice between the two often depends on the specific requirements of the application, including factors such as compatibility needs, performance considerations, and the desired level of flexibility. It’s all about finding the right balance for your specific needs.
