Scroll Axiom Keccak diffs

[naure]

This PR displays the differences from Axiom’s code to PSE/Scroll code of the Keccak circuit. It contains a set of .diff files, generated by a script (also included).

Scope

• Axiom: upgrade-v0.3.0-fixes 2023-03-30 c7bb4a8
• PSE / Scroll: keccak-data-rlc 2023-03-20 scroll-tech/zkevm-circuits@e9584ce
• Helper PR that moves Axiom code into the PSE file structure: Keccak - Split files #7

Summary of Differences

• Challenge API. Axiom and PSE have different variants of the "multiphase" or "challenge" concept.
  • Axiom uses separate functions for phase1 and phase2, rather than a single function in PSE.
  • PSE uses two challenges, shared with other circuits (evm_word, keccak_input).
• Computation of input RLC (data_rlc). Similar idea but different code. PSE#1330.
• Simplification of the function arguments in split and WordParts.
• Different interface. PSE uses the SubCircuit trait in particular.
• In PSE, the KeccakTable is defined in a central table.rs shared with other circuits.
• PSE split from one file to multiple files.
• PSE has minor refactoring around the constant functions (get_num_bits_per_absorb_lookup, variable KECCAK_DEGREE, etc).
• PSE introduced new unittests since the fork (also more in PRs pending merge).
• Axiom copied the non-keccak dependency code from PSE zkevm-circuits into a util module (eth_types, etc).
• Adjustments to imports and item visibilities.

Entry-points and example usage

Axiom

    // Configure.
    let config = KeccakCircuitConfig::new(
        meta,                       // ConstraintSystem
        challenge,                  // Challenge
    );

    // Synthesize.
    config.load_aux_tables(&mut layouter)?;
    let mut challenge = layouter.get_challenge(config.challenge);
    let mut first_pass = true;
    layouter.assign_region(
        || "keccak circuit",
        |mut region| {
            if first_pass {
                first_pass = false;
                return Ok(());
            }
            let (witness, squeeze_digests) = multi_keccak_phase0(&self.inputs, self.capacity());
            config.assign(&mut region, &witness);

            #[cfg(feature = "halo2-axiom")]
            {
                region.next_phase();
                challenge = region.get_challenge(config.challenge);
            }
            multi_keccak_phase1(
                &mut region,
                &config.keccak_table,
                self.inputs.iter().map(|v| v.as_slice()),
                challenge,
                squeeze_digests,
            );
            Ok(())
        },
    )?;

Scroll

    // Configure.
    let config = KeccakCircuitConfig::new(
        meta,                       // ConstraintSystem
        KeccakCircuitConfigArgs {
            keccak_table,           // KeccakTable
            challenges,             // Challenges<Expression<F>>
        },
    );

    // Synthesize.
    let circuit = KeccakCircuit::new(
        num_rows,
        inputs,                     // Vec<Vec<u8>>
    );
    circuit.synthesize_sub(
        &config,
        &challenges,                // Challenges<Value<F>>
        &mut layouter,              // Layouter<F>
    )?;