ZK IR: A Minimalist Instruction Set Architecture for Efficient Zero-Knowledge Proof Generation

Abstract

We present ZK IR, a novel 32-bit instruction set architecture (ISA) specifically designed for efficient zero-knowledge proof generation using STARK protocols. Unlike existing zkVMs that adapt general-purpose ISAs like RISC-V, ZK IR is designed from first principles to minimize proving overhead while maintaining compatibility with modern compiler toolchains. Our key contribution is a rigorous analysis demonstrating that a pure 32-bit register architecture with software-based multi-precision arithmetic outperforms designs with wider registers or specialized field arithmetic units. We achieve approximately 2× reduction in constraint count compared to naive approaches. ZK IR uses the Baby Bear field (31-bit prime) with Plonky3 for proving, and provides an LLVM-based compiler infrastructure enabling developers to write ZK applications in Rust, C, and C++.