Halo2 and the PSE stack
Halo2 started inside Electric Coin Co as the backend for the Orchard pool and escaped into the Privacy and Scaling Explorations group at the Ethereum Foundation. It is a PLONKish backend with no trusted setup, using an inner-product argument and a cycle of curves to do recursion cheaply.
PSE took Halo2 and built a gadget library, a zkEVM, and a general-purpose tooling stack around it. For years it has been the default option when a builder wants customizable PLONKish circuits without shipping a trusted setup ceremony.
The Halo2 circuit DSL is verbose but gives tight control over layout. The stack is slowly being joined and partially replaced by zkVM approaches, but Halo2 gadgets still underpin a surprising amount of shipped code.
- cycle of curves
- PLONKish gadgets
- inner product arguments
- vanilla PLONK without trusted setup
- Ethereum PSE stack
- EP 005CH-012026-03-02
Halo2 and the PSE gadget library
A tour of the Halo2 circuit DSL, the cycle of curves, and the PSE stack that still powers a surprising amount of shipped ZK code.
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