The zkEVM keccak circuit implementation, with some modifications.
Credit goes to https://github.com/privacy-scaling-explorations/zkevm-circuits/tree/main/zkevm-circuits/src/keccak_circuit
Brecht’s SHA-256 circuit implementation, which he modified from the Keccak bit implementation.
Note this circuit does not use lookup tables, only custom gates.
The number of columns are fixed (~130). Unlike keccak, it is not configurable.