Keccak sponge STARK

It contains a row for each absorb step of the sponge.

evm/src/cpu/columns/mod.rs

@@ -3,11 +3,12 @@
 
 use std::borrow::{Borrow, BorrowMut};
 use std::fmt::Debug;
-use std::mem::{size_of, transmute, transmute_copy, ManuallyDrop};
+use std::mem::{size_of, transmute};
 use std::ops::{Index, IndexMut};
 
 use crate::cpu::columns::general::CpuGeneralColumnsView;
 use crate::memory;
+use crate::util::{indices_arr, transmute_no_compile_time_size_checks};
 
 mod general;
 
@@ -157,14 +158,6 @@ pub struct CpuColumnsView<T: Copy> {
 // `u8` is guaranteed to have a `size_of` of 1.
 pub const NUM_CPU_COLUMNS: usize = size_of::<CpuColumnsView<u8>>();
 
-unsafe fn transmute_no_compile_time_size_checks<T, U>(value: T) -> U {
-    debug_assert_eq!(size_of::<T>(), size_of::<U>());
-    // Need ManuallyDrop so that `value` is not dropped by this function.
-    let value = ManuallyDrop::new(value);
-    // Copy the bit pattern. The original value is no longer safe to use.
-    transmute_copy(&value)
-}
-
 impl<T: Copy> From<[T; NUM_CPU_COLUMNS]> for CpuColumnsView<T> {
     fn from(value: [T; NUM_CPU_COLUMNS]) -> Self {
         unsafe { transmute_no_compile_time_size_checks(value) }
@@ -224,12 +217,7 @@ where
 }
 
 const fn make_col_map() -> CpuColumnsView<usize> {
-    let mut indices_arr = [0; NUM_CPU_COLUMNS];
-    let mut i = 0;
-    while i < NUM_CPU_COLUMNS {
-        indices_arr[i] = i;
-        i += 1;
-    }
+    let indices_arr = indices_arr::<NUM_CPU_COLUMNS>();
     unsafe { transmute::<[usize; NUM_CPU_COLUMNS], CpuColumnsView<usize>>(indices_arr) }
 }
 

evm/src/cross_table_lookup.rs

@@ -1,3 +1,4 @@
+use std::borrow::Borrow;
 use std::iter::repeat;
 
 use anyhow::{ensure, Result};
@@ -38,8 +39,10 @@ impl<F: Field> Column<F> {
         }
     }
 
-    pub fn singles<I: IntoIterator<Item = usize>>(cs: I) -> impl Iterator<Item = Self> {
-        cs.into_iter().map(Self::single)
+    pub fn singles<I: IntoIterator<Item = impl Borrow<usize>>>(
+        cs: I,
+    ) -> impl Iterator<Item = Self> {
+        cs.into_iter().map(|c| Self::single(*c.borrow()))
     }
 
     pub fn constant(constant: F) -> Self {
@@ -74,16 +77,20 @@ impl<F: Field> Column<F> {
         Self::linear_combination_with_constant(iter, F::ZERO)
     }
 
-    pub fn le_bits<I: IntoIterator<Item = usize>>(cs: I) -> Self {
-        Self::linear_combination(cs.into_iter().zip(F::TWO.powers()))
+    pub fn le_bits<I: IntoIterator<Item = impl Borrow<usize>>>(cs: I) -> Self {
+        Self::linear_combination(cs.into_iter().map(|c| *c.borrow()).zip(F::TWO.powers()))
     }
 
-    pub fn le_bytes<I: IntoIterator<Item = usize>>(cs: I) -> Self {
-        Self::linear_combination(cs.into_iter().zip(F::from_canonical_u16(256).powers()))
+    pub fn le_bytes<I: IntoIterator<Item = impl Borrow<usize>>>(cs: I) -> Self {
+        Self::linear_combination(
+            cs.into_iter()
+                .map(|c| *c.borrow())
+                .zip(F::from_canonical_u16(256).powers()),
+        )
     }
 
-    pub fn sum<I: IntoIterator<Item = usize>>(cs: I) -> Self {
-        Self::linear_combination(cs.into_iter().zip(repeat(F::ONE)))
+    pub fn sum<I: IntoIterator<Item = impl Borrow<usize>>>(cs: I) -> Self {
+        Self::linear_combination(cs.into_iter().map(|c| *c.borrow()).zip(repeat(F::ONE)))
     }
 
     pub fn eval<FE, P, const D: usize>(&self, v: &[P]) -> P

evm/src/keccak_sponge/columns.rs

@@ -0,0 +1,118 @@
+use std::borrow::{Borrow, BorrowMut};
+use std::mem::{size_of, transmute};
+
+use crate::util::{indices_arr, transmute_no_compile_time_size_checks};
+
+pub(crate) const KECCAK_WIDTH_BYTES: usize = 200;
+pub(crate) const KECCAK_WIDTH_U32S: usize = KECCAK_WIDTH_BYTES / 4;
+pub(crate) const KECCAK_RATE_BITS: usize = 1088;
+pub(crate) const KECCAK_RATE_BYTES: usize = KECCAK_RATE_BITS / 8;
+pub(crate) const KECCAK_RATE_U32S: usize = KECCAK_RATE_BYTES / 4;
+pub(crate) const KECCAK_CAPACITY_BYTES: usize = 64;
+pub(crate) const KECCAK_CAPACITY_U32S: usize = KECCAK_CAPACITY_BYTES / 4;
+
+#[repr(C)]
+#[derive(Eq, PartialEq, Debug)]
+pub(crate) struct KeccakSpongeColumnsView<T: Copy> {
+    /// 1 if this row represents a dummy operation (for padding the table); 0 otherwise.
+    pub is_dummy: T,
+
+    /// 1 if this row represents a full input block, i.e. one in which each byte is an input byte,
+    /// not a padding byte; 0 otherwise.
+    pub is_full_input_block: T,
+
+    /// 1 if this row represents the final block of a sponge, in which case some or all of the bytes
+    /// in the block will be padding bytes; 0 otherwise.
+    pub is_final_block: T,
+
+    // The address at which we will read the input block.
+    pub context: T,
+    pub segment: T,
+    pub virt: T,
+
+    /// The timestamp at which inputs should be read from memory.
+    pub timestamp: T,
+
+    /// The length of the original input, in bytes.
+    pub len: T,
+
+    /// The number of input bytes that have already been absorbed prior to this block.
+    pub already_absorbed_bytes: T,
+
+    /// If this row represents a final block row, the `i`th entry should be 1 if the final chunk of
+    /// input has length `i` (in other words if `len - already_absorbed == i`), otherwise 0.
+    ///
+    /// If this row represents a full input block, this should contain all 0s.
+    pub is_final_input_len: [T; KECCAK_RATE_BYTES],
+
+    /// The initial rate bits of the sponge, at the start of this step.
+    pub original_rate_bits: [T; KECCAK_RATE_BITS],
+
+    /// The capacity bits of the sponge, encoded as 32-bit chunks, at the start of this step.
+    pub original_capacity_u32s: [T; KECCAK_CAPACITY_U32S],
+
+    /// The block being absorbed, which may contain input bytes and/or padding bytes.
+    pub block_bits: [T; KECCAK_RATE_BITS],
+
+    /// The rate bits of the sponge, after the current block is xor'd in, but before the permutation
+    /// is applied.
+    pub xored_rate_u32s: [T; KECCAK_RATE_U32S],
+
+    /// The entire state (rate + capacity) of the sponge, encoded as 32-bit chunks, after the
+    /// permutation is applied.
+    pub updated_state_u32s: [T; KECCAK_WIDTH_U32S],
+}
+
+// `u8` is guaranteed to have a `size_of` of 1.
+pub const NUM_KECCAK_SPONGE_COLUMNS: usize = size_of::<KeccakSpongeColumnsView<u8>>();
+
+impl<T: Copy> From<[T; NUM_KECCAK_SPONGE_COLUMNS]> for KeccakSpongeColumnsView<T> {
+    fn from(value: [T; NUM_KECCAK_SPONGE_COLUMNS]) -> Self {
+        unsafe { transmute_no_compile_time_size_checks(value) }
+    }
+}
+
+impl<T: Copy> From<KeccakSpongeColumnsView<T>> for [T; NUM_KECCAK_SPONGE_COLUMNS] {
+    fn from(value: KeccakSpongeColumnsView<T>) -> Self {
+        unsafe { transmute_no_compile_time_size_checks(value) }
+    }
+}
+
+impl<T: Copy> Borrow<KeccakSpongeColumnsView<T>> for [T; NUM_KECCAK_SPONGE_COLUMNS] {
+    fn borrow(&self) -> &KeccakSpongeColumnsView<T> {
+        unsafe { transmute(self) }
+    }
+}
+
+impl<T: Copy> BorrowMut<KeccakSpongeColumnsView<T>> for [T; NUM_KECCAK_SPONGE_COLUMNS] {
+    fn borrow_mut(&mut self) -> &mut KeccakSpongeColumnsView<T> {
+        unsafe { transmute(self) }
+    }
+}
+
+impl<T: Copy> Borrow<[T; NUM_KECCAK_SPONGE_COLUMNS]> for KeccakSpongeColumnsView<T> {
+    fn borrow(&self) -> &[T; NUM_KECCAK_SPONGE_COLUMNS] {
+        unsafe { transmute(self) }
+    }
+}
+
+impl<T: Copy> BorrowMut<[T; NUM_KECCAK_SPONGE_COLUMNS]> for KeccakSpongeColumnsView<T> {
+    fn borrow_mut(&mut self) -> &mut [T; NUM_KECCAK_SPONGE_COLUMNS] {
+        unsafe { transmute(self) }
+    }
+}
+
+impl<T: Copy + Default> Default for KeccakSpongeColumnsView<T> {
+    fn default() -> Self {
+        [T::default(); NUM_KECCAK_SPONGE_COLUMNS].into()
+    }
+}
+
+const fn make_col_map() -> KeccakSpongeColumnsView<usize> {
+    let indices_arr = indices_arr::<NUM_KECCAK_SPONGE_COLUMNS>();
+    unsafe {
+        transmute::<[usize; NUM_KECCAK_SPONGE_COLUMNS], KeccakSpongeColumnsView<usize>>(indices_arr)
+    }
+}
+
+pub(crate) const KECCAK_SPONGE_COL_MAP: KeccakSpongeColumnsView<usize> = make_col_map();

evm/src/keccak_sponge/keccak_sponge_stark.rs

@@ -0,0 +1,441 @@
+use std::borrow::Borrow;
+use std::iter;
+use std::marker::PhantomData;
+use std::mem::size_of;
+
+use itertools::Itertools;
+use plonky2::field::extension::{Extendable, FieldExtension};
+use plonky2::field::packed::PackedField;
+use plonky2::field::polynomial::PolynomialValues;
+use plonky2::field::types::Field;
+use plonky2::hash::hash_types::RichField;
+use plonky2::iop::ext_target::ExtensionTarget;
+use plonky2::timed;
+use plonky2::util::timing::TimingTree;
+
+use crate::constraint_consumer::{ConstraintConsumer, RecursiveConstraintConsumer};
+use crate::cpu::kernel::keccak_util::keccakf_u32s;
+use crate::cross_table_lookup::Column;
+use crate::keccak_sponge::columns::*;
+use crate::memory::segments::Segment;
+use crate::stark::Stark;
+use crate::util::{trace_rows_to_poly_values, u32_from_le_bits, u32_to_le_bits, u8_to_le_bits};
+use crate::vars::StarkEvaluationTargets;
+use crate::vars::StarkEvaluationVars;
+
+#[allow(unused)] // TODO: Should be used soon.
+pub(crate) fn ctl_looked_data<F: Field>() -> Vec<Column<F>> {
+    let cols = KECCAK_SPONGE_COL_MAP;
+    let outputs = Column::singles(&cols.updated_state_u32s[..KECCAK_RATE_U32S]);
+    Column::singles([
+        cols.context,
+        cols.segment,
+        cols.virt,
+        cols.timestamp,
+        cols.len,
+    ])
+    .chain(outputs)
+    .collect()
+}
+
+#[allow(unused)] // TODO: Should be used soon.
+pub(crate) fn ctl_looking_keccak<F: Field>() -> Vec<Column<F>> {
+    let input_rate_cols = (0..KECCAK_WIDTH_U32S)
+        .map(|i| Column::le_bits(&KECCAK_SPONGE_COL_MAP.original_rate_bits[i * 32..(i + 1) * 32]));
+    let input_capacity_cols = Column::singles(
+        (0..KECCAK_WIDTH_U32S).map(|i| KECCAK_SPONGE_COL_MAP.original_capacity_u32s[i]),
+    );
+    let output_cols = Column::singles(
+        (0..KECCAK_WIDTH_U32S).map(|i| KECCAK_SPONGE_COL_MAP.updated_state_u32s[i]),
+    );
+    input_rate_cols
+        .chain(input_capacity_cols)
+        .chain(output_cols)
+        .collect()
+}
+
+#[allow(unused)] // TODO: Should be used soon.
+pub(crate) fn ctl_looking_memory<F: Field>(i: usize) -> Vec<Column<F>> {
+    let cols = KECCAK_SPONGE_COL_MAP;
+
+    let mut res = vec![Column::constant(F::ONE)]; // is_read
+
+    res.extend(Column::singles([cols.context, cols.segment, cols.virt]));
+
+    // The i'th input byte being read.
+    res.push(Column::le_bits(&cols.block_bits[i * 8..(i + 1) * 8]));
+
+    // Since we're reading a single byte, the higher limbs must be zero.
+    res.extend((1..8).map(|_| Column::zero()));
+
+    res.push(Column::single(cols.timestamp));
+
+    assert_eq!(
+        res.len(),
+        crate::memory::memory_stark::ctl_data::<F>().len()
+    );
+    res
+}
+
+#[allow(unused)] // TODO: Should be used soon.
+pub(crate) fn ctl_looked_filter<F: Field>() -> Column<F> {
+    // The CPU table is only interested in our final-block rows, since those contain the final
+    // sponge output.
+    Column::single(KECCAK_SPONGE_COL_MAP.is_final_block)
+}
+
+#[allow(unused)] // TODO: Should be used soon.
+/// CTL filter for reading the `i`th byte of input from memory.
+pub(crate) fn ctl_looking_memory_filter<F: Field>(i: usize) -> Column<F> {
+    // We perform the `i`th read if either
+    // - this is a full input block, or
+    // - this is a final block of length `i` or greater
+    let cols = KECCAK_SPONGE_COL_MAP;
+    Column::sum(iter::once(&cols.is_full_input_block).chain(&cols.is_final_input_len[i..]))
+}
+
+/// Information about a Keccak sponge operation needed for witness generation.
+#[derive(Debug)]
+pub(crate) struct KeccakSpongeOp {
+    // The address at which inputs are read.
+    pub(crate) context: usize,
+    pub(crate) segment: Segment,
+    pub(crate) virt: usize,
+
+    /// The timestamp at which inputs are read.
+    pub(crate) timestamp: usize,
+
+    /// The length of the input, in bytes.
+    pub(crate) len: usize,
+
+    /// The input that was read.
+    pub(crate) input: Vec<u8>,
+}
+
+#[derive(Copy, Clone, Default)]
+pub(crate) struct KeccakSpongeStark<F, const D: usize> {
+    f: PhantomData<F>,
+}
+
+impl<F: RichField + Extendable<D>, const D: usize> KeccakSpongeStark<F, D> {
+    #[allow(unused)] // TODO: Should be used soon.
+    pub(crate) fn generate_trace(
+        &self,
+        operations: Vec<KeccakSpongeOp>,
+        min_rows: usize,
+    ) -> Vec<PolynomialValues<F>> {
+        let mut timing = TimingTree::new("generate trace", log::Level::Debug);
+
+        // Generate the witness row-wise.
+        let trace_rows = timed!(
+            &mut timing,
+            "generate trace rows",
+            self.generate_trace_rows(operations, min_rows)
+        );
+
+        let trace_polys = timed!(
+            &mut timing,
+            "convert to PolynomialValues",
+            trace_rows_to_poly_values(trace_rows)
+        );
+
+        timing.print();
+        trace_polys
+    }
+
+    fn generate_trace_rows(
+        &self,
+        operations: Vec<KeccakSpongeOp>,
+        min_rows: usize,
+    ) -> Vec<[F; NUM_KECCAK_SPONGE_COLUMNS]> {
+        let mut rows = vec![];
+        for op in operations {
+            rows.extend(self.generate_rows_for_op(op));
+        }
+
+        let num_rows = rows.len().max(min_rows).next_power_of_two();
+        let padding_row = self.generate_padding_row();
+        for _ in rows.len()..num_rows {
+            rows.push(padding_row);
+        }
+        rows
+    }
+
+    fn generate_rows_for_op(&self, op: KeccakSpongeOp) -> Vec<[F; NUM_KECCAK_SPONGE_COLUMNS]> {
+        let mut rows = vec![];
+
+        let mut sponge_state = [0u32; KECCAK_WIDTH_U32S];
+
+        let mut input_blocks = op.input.chunks_exact(KECCAK_RATE_BYTES);
+        let mut already_absorbed_bytes = 0;
+        for block in input_blocks.by_ref() {
+            let row = self.generate_full_input_row(
+                &op,
+                already_absorbed_bytes,
+                sponge_state,
+                block.try_into().unwrap(),
+            );
+
+            // xor block into sponge_state's rate elements.
+            let block_u32s = block
+                .chunks(size_of::<u32>())
+                .map(|chunk| u32::from_le_bytes(chunk.try_into().unwrap()));
+            for (state_u32, block_u32) in sponge_state.iter_mut().zip(block_u32s) {
+                *state_u32 ^= block_u32;
+            }
+
+            sponge_state = row.updated_state_u32s.map(|f| f.to_canonical_u64() as u32);
+
+            rows.push(row.into());
+            already_absorbed_bytes += KECCAK_RATE_BYTES;
+        }
+
+        rows.push(
+            self.generate_final_row(
+                &op,
+                already_absorbed_bytes,
+                sponge_state,
+                input_blocks.remainder(),
+            )
+            .into(),
+        );
+
+        rows
+    }
+
+    fn generate_full_input_row(
+        &self,
+        op: &KeccakSpongeOp,
+        already_absorbed_bytes: usize,
+        sponge_state: [u32; KECCAK_WIDTH_U32S],
+        block: [u8; KECCAK_RATE_BYTES],
+    ) -> KeccakSpongeColumnsView<F> {
+        let mut row = KeccakSpongeColumnsView {
+            is_full_input_block: F::ONE,
+            ..Default::default()
+        };
+
+        row.block_bits = block
+            .into_iter()
+            .flat_map(u8_to_le_bits)
+            .map(F::from_bool)
+            .collect_vec()
+            .try_into()
+            .unwrap();
+
+        Self::generate_common_fields(&mut row, op, already_absorbed_bytes, sponge_state);
+        row
+    }
+
+    fn generate_final_row(
+        &self,
+        op: &KeccakSpongeOp,
+        already_absorbed_bytes: usize,
+        sponge_state: [u32; KECCAK_WIDTH_U32S],
+        final_inputs: &[u8],
+    ) -> KeccakSpongeColumnsView<F> {
+        assert_eq!(already_absorbed_bytes + final_inputs.len(), op.len);
+
+        let mut row = KeccakSpongeColumnsView {
+            is_final_block: F::ONE,
+            ..Default::default()
+        };
+
+        let final_input_bits = final_inputs
+            .iter()
+            .flat_map(|x| u8_to_le_bits(*x))
+            .map(F::from_bool);
+        for (block_bit, input_bit) in row.block_bits.iter_mut().zip(final_input_bits) {
+            *block_bit = input_bit;
+        }
+        // pad10*1 rule
+        row.block_bits[final_inputs.len() * 8] = F::ONE;
+        row.block_bits[KECCAK_RATE_BITS - 1] = F::ONE;
+
+        row.is_final_input_len[final_inputs.len()] = F::ONE;
+
+        Self::generate_common_fields(&mut row, op, already_absorbed_bytes, sponge_state);
+        row
+    }
+
+    /// Generate fields that are common to both full-input-block rows and final-block rows.
+    fn generate_common_fields(
+        row: &mut KeccakSpongeColumnsView<F>,
+        op: &KeccakSpongeOp,
+        already_absorbed_bytes: usize,
+        mut sponge_state: [u32; KECCAK_WIDTH_U32S],
+    ) {
+        row.context = F::from_canonical_usize(op.context);
+        row.segment = F::from_canonical_usize(op.segment as usize);
+        row.virt = F::from_canonical_usize(op.virt);
+        row.timestamp = F::from_canonical_usize(op.timestamp);
+        row.len = F::from_canonical_usize(op.len);
+        row.already_absorbed_bytes = F::from_canonical_usize(already_absorbed_bytes);
+
+        row.original_rate_bits = sponge_state[..KECCAK_RATE_U32S]
+            .iter()
+            .flat_map(|x| u32_to_le_bits(*x))
+            .map(F::from_bool)
+            .collect_vec()
+            .try_into()
+            .unwrap();
+
+        row.original_capacity_u32s = sponge_state[KECCAK_RATE_U32S..]
+            .iter()
+            .map(|x| F::from_canonical_u32(*x))
+            .collect_vec()
+            .try_into()
+            .unwrap();
+
+        let block_u32s = (0..KECCAK_RATE_U32S).map(|i| {
+            u32_from_le_bits(
+                row.block_bits[i * 32..(i + 1) * 32]
+                    .iter()
+                    .map(|f| *f == F::ONE)
+                    .collect_vec()
+                    .try_into()
+                    .unwrap(),
+            )
+        });
+
+        // xor in the block
+        for (state_i, block_i) in sponge_state.iter_mut().zip(block_u32s) {
+            *state_i ^= block_i;
+        }
+        let xored_rate_u32s: [u32; KECCAK_RATE_U32S] = sponge_state[..KECCAK_RATE_U32S]
+            .to_vec()
+            .try_into()
+            .unwrap();
+        row.xored_rate_u32s = xored_rate_u32s.map(F::from_canonical_u32);
+
+        keccakf_u32s(&mut sponge_state);
+        row.updated_state_u32s = sponge_state.map(F::from_canonical_u32);
+    }
+
+    fn generate_padding_row(&self) -> [F; NUM_KECCAK_SPONGE_COLUMNS] {
+        // We just need is_dummy = 1; the other fields will have no effect.
+        KeccakSpongeColumnsView {
+            is_dummy: F::ONE,
+            ..Default::default()
+        }
+        .into()
+    }
+}
+
+impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for KeccakSpongeStark<F, D> {
+    const COLUMNS: usize = NUM_KECCAK_SPONGE_COLUMNS;
+
+    fn eval_packed_generic<FE, P, const D2: usize>(
+        &self,
+        vars: StarkEvaluationVars<FE, P, { Self::COLUMNS }>,
+        _yield_constr: &mut ConstraintConsumer<P>,
+    ) where
+        FE: FieldExtension<D2, BaseField = F>,
+        P: PackedField<Scalar = FE>,
+    {
+        let _local_values: &KeccakSpongeColumnsView<P> = vars.local_values.borrow();
+
+        // TODO: Each flag (full-input block, final block or dummy row) must be boolean.
+        // TODO: before_rate_bits, block_bits and is_final_input_len must contain booleans.
+
+        // TODO: Sum of row type flags (full-input block, final block or dummy row) should equal 1.
+
+        // TODO: Sum of is_final_input_len should equal is_final_block (which will be 0 or 1).
+
+        // TODO: If this is the first row, the original sponge state should be 0 and already_absorbed_bytes = 0.
+        // TODO: If this is a final block, the next row's original sponge state should be 0 and already_absorbed_bytes = 0.
+
+        // TODO: If this is a full-input block, the next row's address, time and len must match.
+        // TODO: If this is a full-input block, the next row's "before" should match our "after" state.
+        // TODO: If this is a full-input block, the next row's already_absorbed_bytes should be ours plus 136.
+
+        // TODO: A dummy row is always followed by another dummy row, so the prover can't put dummy rows "in between" to avoid the above checks.
+
+        // TODO: is_final_input_len implies `len - already_absorbed == i`.
+    }
+
+    fn eval_ext_circuit(
+        &self,
+        _builder: &mut plonky2::plonk::circuit_builder::CircuitBuilder<F, D>,
+        vars: StarkEvaluationTargets<D, { Self::COLUMNS }>,
+        _yield_constr: &mut RecursiveConstraintConsumer<F, D>,
+    ) {
+        let _local_values: &KeccakSpongeColumnsView<ExtensionTarget<D>> =
+            vars.local_values.borrow();
+
+        // TODO
+    }
+
+    fn constraint_degree(&self) -> usize {
+        3
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::borrow::Borrow;
+
+    use anyhow::Result;
+    use itertools::Itertools;
+    use keccak_hash::keccak;
+    use plonky2::field::goldilocks_field::GoldilocksField;
+    use plonky2::field::types::PrimeField64;
+    use plonky2::plonk::config::{GenericConfig, PoseidonGoldilocksConfig};
+
+    use crate::keccak_sponge::columns::KeccakSpongeColumnsView;
+    use crate::keccak_sponge::keccak_sponge_stark::{KeccakSpongeOp, KeccakSpongeStark};
+    use crate::memory::segments::Segment;
+    use crate::stark_testing::{test_stark_circuit_constraints, test_stark_low_degree};
+
+    #[test]
+    fn test_stark_degree() -> Result<()> {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = <C as GenericConfig<D>>::F;
+        type S = KeccakSpongeStark<F, D>;
+
+        let stark = S::default();
+        test_stark_low_degree(stark)
+    }
+
+    #[test]
+    fn test_stark_circuit() -> Result<()> {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = <C as GenericConfig<D>>::F;
+        type S = KeccakSpongeStark<F, D>;
+
+        let stark = S::default();
+        test_stark_circuit_constraints::<F, C, S, D>(stark)
+    }
+
+    #[test]
+    fn test_generation() -> Result<()> {
+        const D: usize = 2;
+        type F = GoldilocksField;
+        type S = KeccakSpongeStark<F, D>;
+
+        let input = vec![1, 2, 3];
+        let expected_output = keccak(&input);
+
+        let op = KeccakSpongeOp {
+            context: 0,
+            segment: Segment::Code,
+            virt: 0,
+            timestamp: 0,
+            len: input.len(),
+            input,
+        };
+        let stark = S::default();
+        let rows = stark.generate_rows_for_op(op);
+        assert_eq!(rows.len(), 1);
+        let last_row: &KeccakSpongeColumnsView<F> = rows.last().unwrap().borrow();
+        let output = last_row.updated_state_u32s[..8]
+            .iter()
+            .flat_map(|x| (x.to_canonical_u64() as u32).to_le_bytes())
+            .collect_vec();
+
+        assert_eq!(output, expected_output.0);
+        Ok(())
+    }
+}

evm/src/keccak_sponge/mod.rs

@@ -0,0 +1,6 @@
+//! The Keccak sponge STARK is used to hash a variable amount of data which is read from memory.
+//! It connects to the memory STARK to read input data, and to the Keccak-f STARK to evaluate the
+//! permutation at each absorption step.
+
+pub mod columns;
+pub mod keccak_sponge_stark;

evm/src/lib.rs

@@ -15,6 +15,7 @@ pub mod generation;
 mod get_challenges;
 pub mod keccak;
 pub mod keccak_memory;
+pub mod keccak_sponge;
 pub mod logic;
 pub mod lookup;
 pub mod memory;

evm/src/stark_testing.rs

@@ -60,17 +60,20 @@ where
         })
         .collect::<Vec<_>>();
 
-    let constraint_eval_degree = PolynomialValues::new(constraint_evals).degree();
-    let maximum_degree = WITNESS_SIZE * stark.constraint_degree() - 1;
+    let constraint_poly_values = PolynomialValues::new(constraint_evals);
+    if !constraint_poly_values.is_zero() {
+        let constraint_eval_degree = constraint_poly_values.degree();
+        let maximum_degree = WITNESS_SIZE * stark.constraint_degree() - 1;
 
-    ensure!(
-        constraint_eval_degree <= maximum_degree,
-        "Expected degrees at most {} * {} - 1 = {}, actual {:?}",
-        WITNESS_SIZE,
-        stark.constraint_degree(),
-        maximum_degree,
-        constraint_eval_degree
-    );
+        ensure!(
+            constraint_eval_degree <= maximum_degree,
+            "Expected degrees at most {} * {} - 1 = {}, actual {:?}",
+            WITNESS_SIZE,
+            stark.constraint_degree(),
+            maximum_degree,
+            constraint_eval_degree
+        );
+    }
 
     Ok(())
 }

evm/src/util.rs

@@ -1,3 +1,5 @@
+use std::mem::{size_of, transmute_copy, ManuallyDrop};
+
 use ethereum_types::{H160, U256};
 use itertools::Itertools;
 use plonky2::field::extension::Extendable;
@@ -67,3 +69,35 @@ pub(crate) fn h160_limbs<F: Field>(h160: H160) -> [F; 5] {
         .try_into()
         .unwrap()
 }
+
+pub(crate) fn u8_to_le_bits(x: u8) -> [bool; 8] {
+    std::array::from_fn(|i| ((x >> i) & 1) != 0)
+}
+
+pub(crate) fn u32_to_le_bits(x: u32) -> [bool; 32] {
+    std::array::from_fn(|i| ((x >> i) & 1) != 0)
+}
+
+pub(crate) fn u32_from_le_bits(bits: [bool; 32]) -> u32 {
+    bits.into_iter()
+        .rev()
+        .fold(0, |acc, b| (acc << 1) | b as u32)
+}
+
+pub(crate) const fn indices_arr<const N: usize>() -> [usize; N] {
+    let mut indices_arr = [0; N];
+    let mut i = 0;
+    while i < N {
+        indices_arr[i] = i;
+        i += 1;
+    }
+    indices_arr
+}
+
+pub(crate) unsafe fn transmute_no_compile_time_size_checks<T, U>(value: T) -> U {
+    debug_assert_eq!(size_of::<T>(), size_of::<U>());
+    // Need ManuallyDrop so that `value` is not dropped by this function.
+    let value = ManuallyDrop::new(value);
+    // Copy the bit pattern. The original value is no longer safe to use.
+    transmute_copy(&value)
+}

field/src/polynomial/mod.rs

@@ -37,6 +37,10 @@ impl<F: Field> PolynomialValues<F> {
         Self::constant(F::ZERO, len)
     }
 
+    pub fn is_zero(&self) -> bool {
+        self.values.iter().all(|x| x.is_zero())
+    }
+
     /// Returns the polynomial whole value is one at the given index, and zero elsewhere.
     pub fn selector(len: usize, index: usize) -> Self {
         let mut result = Self::zero(len);