plonky2/evm/src/proof.rs

use ethereum_types::{Address, H256, U256};
use itertools::Itertools;
use plonky2::field::extension::{Extendable, FieldExtension};
use plonky2::fri::oracle::PolynomialBatch;
use plonky2::fri::proof::{FriChallenges, FriChallengesTarget, FriProof, FriProofTarget};
use plonky2::fri::structure::{
    FriOpeningBatch, FriOpeningBatchTarget, FriOpenings, FriOpeningsTarget,
};
use plonky2::hash::hash_types::{MerkleCapTarget, RichField};
use plonky2::hash::hashing::SPONGE_WIDTH;
use plonky2::hash::merkle_tree::MerkleCap;
use plonky2::iop::ext_target::ExtensionTarget;
use plonky2::iop::target::Target;
use plonky2::plonk::config::GenericConfig;
use plonky2_maybe_rayon::*;
use serde::{Deserialize, Serialize};

use crate::all_stark::NUM_TABLES;
use crate::config::StarkConfig;
use crate::permutation::GrandProductChallengeSet;

/// A STARK proof for each table, plus some metadata used to create recursive wrapper proofs.
#[derive(Debug, Clone)]
pub struct AllProof<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize> {
    pub stark_proofs: [StarkProofWithMetadata<F, C, D>; NUM_TABLES],
    pub(crate) ctl_challenges: GrandProductChallengeSet<F>,
    pub public_values: PublicValues,
}

impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize> AllProof<F, C, D> {
    pub fn degree_bits(&self, config: &StarkConfig) -> [usize; NUM_TABLES] {
        core::array::from_fn(|i| self.stark_proofs[i].proof.recover_degree_bits(config))
    }
}

pub(crate) struct AllProofChallenges<F: RichField + Extendable<D>, const D: usize> {
    pub stark_challenges: [StarkProofChallenges<F, D>; NUM_TABLES],
    pub ctl_challenges: GrandProductChallengeSet<F>,
}

#[allow(unused)] // TODO: should be used soon
pub(crate) struct AllChallengerState<F: RichField + Extendable<D>, const D: usize> {
    /// Sponge state of the challenger before starting each proof,
    /// along with the final state after all proofs are done. This final state isn't strictly needed.
    pub states: [[F; SPONGE_WIDTH]; NUM_TABLES + 1],
    pub ctl_challenges: GrandProductChallengeSet<F>,
}

/// Memory values which are public.
#[derive(Debug, Clone, Default)]
pub struct PublicValues {
    pub trie_roots_before: TrieRoots,
    pub trie_roots_after: TrieRoots,
    pub block_metadata: BlockMetadata,
}

#[derive(Debug, Clone, Default)]
pub struct TrieRoots {
    pub state_root: H256,
    pub transactions_root: H256,
    pub receipts_root: H256,
}

#[derive(Debug, Clone, Default, Deserialize, Serialize)]
pub struct BlockMetadata {
    pub block_beneficiary: Address,
    pub block_timestamp: U256,
    pub block_number: U256,
    pub block_difficulty: U256,
    pub block_gaslimit: U256,
    pub block_chain_id: U256,
    pub block_base_fee: U256,
}

/// Memory values which are public.
/// Note: All the larger integers are encoded with 32-bit limbs in little-endian order.
pub struct PublicValuesTarget {
    pub trie_roots_before: TrieRootsTarget,
    pub trie_roots_after: TrieRootsTarget,
    pub block_metadata: BlockMetadataTarget,
}

pub struct TrieRootsTarget {
    pub state_root: [Target; 8],
    pub transactions_root: [Target; 8],
    pub receipts_root: [Target; 8],
}

pub struct BlockMetadataTarget {
    pub block_beneficiary: [Target; 5],
    pub block_timestamp: Target,
    pub block_number: Target,
    pub block_difficulty: Target,
    pub block_gaslimit: Target,
    pub block_chain_id: Target,
    pub block_base_fee: Target,
}

#[derive(Debug, Clone)]
pub struct StarkProof<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize> {
    /// Merkle cap of LDEs of trace values.
    pub trace_cap: MerkleCap<F, C::Hasher>,
    /// Merkle cap of LDEs of permutation Z values.
    pub permutation_ctl_zs_cap: MerkleCap<F, C::Hasher>,
    /// Merkle cap of LDEs of trace values.
    pub quotient_polys_cap: MerkleCap<F, C::Hasher>,
    /// Purported values of each polynomial at the challenge point.
    pub openings: StarkOpeningSet<F, D>,
    /// A batch FRI argument for all openings.
    pub opening_proof: FriProof<F, C::Hasher, D>,
}

/// A `StarkProof` along with some metadata about the initial Fiat-Shamir state, which is used when
/// creating a recursive wrapper proof around a STARK proof.
#[derive(Debug, Clone)]
pub struct StarkProofWithMetadata<F, C, const D: usize>
where
    F: RichField + Extendable<D>,
    C: GenericConfig<D, F = F>,
{
    pub(crate) init_challenger_state: [F; SPONGE_WIDTH],
    pub(crate) proof: StarkProof<F, C, D>,
}

impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize> StarkProof<F, C, D> {
    /// Recover the length of the trace from a STARK proof and a STARK config.
    pub fn recover_degree_bits(&self, config: &StarkConfig) -> usize {
        let initial_merkle_proof = &self.opening_proof.query_round_proofs[0]
            .initial_trees_proof
            .evals_proofs[0]
            .1;
        let lde_bits = config.fri_config.cap_height + initial_merkle_proof.siblings.len();
        lde_bits - config.fri_config.rate_bits
    }

    pub fn num_ctl_zs(&self) -> usize {
        self.openings.ctl_zs_last.len()
    }
}

pub struct StarkProofTarget<const D: usize> {
    pub trace_cap: MerkleCapTarget,
    pub permutation_ctl_zs_cap: MerkleCapTarget,
    pub quotient_polys_cap: MerkleCapTarget,
    pub openings: StarkOpeningSetTarget<D>,
    pub opening_proof: FriProofTarget<D>,
}

impl<const D: usize> StarkProofTarget<D> {
    /// Recover the length of the trace from a STARK proof and a STARK config.
    pub fn recover_degree_bits(&self, config: &StarkConfig) -> usize {
        let initial_merkle_proof = &self.opening_proof.query_round_proofs[0]
            .initial_trees_proof
            .evals_proofs[0]
            .1;
        let lde_bits = config.fri_config.cap_height + initial_merkle_proof.siblings.len();
        lde_bits - config.fri_config.rate_bits
    }
}

pub(crate) struct StarkProofChallenges<F: RichField + Extendable<D>, const D: usize> {
    /// Randomness used in any permutation arguments.
    pub permutation_challenge_sets: Option<Vec<GrandProductChallengeSet<F>>>,

    /// Random values used to combine STARK constraints.
    pub stark_alphas: Vec<F>,

    /// Point at which the STARK polynomials are opened.
    pub stark_zeta: F::Extension,

    pub fri_challenges: FriChallenges<F, D>,
}

pub(crate) struct StarkProofChallengesTarget<const D: usize> {
    pub permutation_challenge_sets: Option<Vec<GrandProductChallengeSet<Target>>>,
    pub stark_alphas: Vec<Target>,
    pub stark_zeta: ExtensionTarget<D>,
    pub fri_challenges: FriChallengesTarget<D>,
}

/// Purported values of each polynomial at the challenge point.
#[derive(Debug, Clone)]
pub struct StarkOpeningSet<F: RichField + Extendable<D>, const D: usize> {
    /// Openings of trace polynomials at `zeta`.
    pub local_values: Vec<F::Extension>,
    /// Openings of trace polynomials at `g * zeta`.
    pub next_values: Vec<F::Extension>,
    /// Openings of permutations and cross-table lookups `Z` polynomials at `zeta`.
    pub permutation_ctl_zs: Vec<F::Extension>,
    /// Openings of permutations and cross-table lookups `Z` polynomials at `g * zeta`.
    pub permutation_ctl_zs_next: Vec<F::Extension>,
    /// Openings of cross-table lookups `Z` polynomials at `g^-1`.
    pub ctl_zs_last: Vec<F>,
    /// Openings of quotient polynomials at `zeta`.
    pub quotient_polys: Vec<F::Extension>,
}

impl<F: RichField + Extendable<D>, const D: usize> StarkOpeningSet<F, D> {
    pub fn new<C: GenericConfig<D, F = F>>(
        zeta: F::Extension,
        g: F,
        trace_commitment: &PolynomialBatch<F, C, D>,
        permutation_ctl_zs_commitment: &PolynomialBatch<F, C, D>,
        quotient_commitment: &PolynomialBatch<F, C, D>,
        degree_bits: usize,
        num_permutation_zs: usize,
    ) -> Self {
        let eval_commitment = |z: F::Extension, c: &PolynomialBatch<F, C, D>| {
            c.polynomials
                .par_iter()
                .map(|p| p.to_extension().eval(z))
                .collect::<Vec<_>>()
        };
        let eval_commitment_base = |z: F, c: &PolynomialBatch<F, C, D>| {
            c.polynomials
                .par_iter()
                .map(|p| p.eval(z))
                .collect::<Vec<_>>()
        };
        let zeta_next = zeta.scalar_mul(g);
        Self {
            local_values: eval_commitment(zeta, trace_commitment),
            next_values: eval_commitment(zeta_next, trace_commitment),
            permutation_ctl_zs: eval_commitment(zeta, permutation_ctl_zs_commitment),
            permutation_ctl_zs_next: eval_commitment(zeta_next, permutation_ctl_zs_commitment),
            ctl_zs_last: eval_commitment_base(
                F::primitive_root_of_unity(degree_bits).inverse(),
                permutation_ctl_zs_commitment,
            )[num_permutation_zs..]
                .to_vec(),
            quotient_polys: eval_commitment(zeta, quotient_commitment),
        }
    }

    pub(crate) fn to_fri_openings(&self) -> FriOpenings<F, D> {
        let zeta_batch = FriOpeningBatch {
            values: self
                .local_values
                .iter()
                .chain(&self.permutation_ctl_zs)
                .chain(&self.quotient_polys)
                .copied()
                .collect_vec(),
        };
        let zeta_next_batch = FriOpeningBatch {
            values: self
                .next_values
                .iter()
                .chain(&self.permutation_ctl_zs_next)
                .copied()
                .collect_vec(),
        };
        debug_assert!(!self.ctl_zs_last.is_empty());
        let ctl_last_batch = FriOpeningBatch {
            values: self
                .ctl_zs_last
                .iter()
                .copied()
                .map(F::Extension::from_basefield)
                .collect(),
        };

        FriOpenings {
            batches: vec![zeta_batch, zeta_next_batch, ctl_last_batch],
        }
    }
}

pub struct StarkOpeningSetTarget<const D: usize> {
    pub local_values: Vec<ExtensionTarget<D>>,
    pub next_values: Vec<ExtensionTarget<D>>,
    pub permutation_ctl_zs: Vec<ExtensionTarget<D>>,
    pub permutation_ctl_zs_next: Vec<ExtensionTarget<D>>,
    pub ctl_zs_last: Vec<Target>,
    pub quotient_polys: Vec<ExtensionTarget<D>>,
}

impl<const D: usize> StarkOpeningSetTarget<D> {
    pub(crate) fn to_fri_openings(&self, zero: Target) -> FriOpeningsTarget<D> {
        let zeta_batch = FriOpeningBatchTarget {
            values: self
                .local_values
                .iter()
                .chain(&self.permutation_ctl_zs)
                .chain(&self.quotient_polys)
                .copied()
                .collect_vec(),
        };
        let zeta_next_batch = FriOpeningBatchTarget {
            values: self
                .next_values
                .iter()
                .chain(&self.permutation_ctl_zs_next)
                .copied()
                .collect_vec(),
        };
        debug_assert!(!self.ctl_zs_last.is_empty());
        let ctl_last_batch = FriOpeningBatchTarget {
            values: self
                .ctl_zs_last
                .iter()
                .copied()
                .map(|t| t.to_ext_target(zero))
                .collect(),
        };

        FriOpeningsTarget {
            batches: vec![zeta_batch, zeta_next_batch, ctl_last_batch],
        }
    }
}