Hobbit: Space-Efficient zkSNARK with Optimal Prover Time
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Presented at USENIX Security 2025 by
Zero-knowledge succinct non-interactive arguments (zkSNARKs) are notorious for their large prover space requirements, which almost prohibits their use for really large instances. Space-efficient zkSNARKs aim to address this by limiting the prover space usage, without critical sacrifices to its runtime. In this work, we introduce Hobbit, the only existing space-efficient zkSNARK that achieves optimal prover time O(|C|) for an arithmetic circuit C. At the same time, Hobbit is the first transparent and post-quantum secure construction of its kind. Moreover, our experimental evaluation shows that Hobbit outperforms all prior general-purpose space-efficient zkSNARKs in the literature across four different applications (arbitrary arithmetic circuits, inference of pruned Multi-Layer Perceptron, batch AES128 evaluation, and select-and-aggregate SQL query) by x8-x56 in terms or prover time while requiring up to x23 less total space.