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Digest-generic MerkleTreeGadget #167

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merged 6 commits into from
Jan 20, 2023
Merged

Digest-generic MerkleTreeGadget #167

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e5e9925
Add an associated type DigestGadget to MerkleTreeGadget
tessico Dec 19, 2022
364dadf
make struct fields private
tessico Jan 18, 2023
502abbb
replace usages of RescueGadget with generic DigestGadget
tessico Jan 18, 2023
2e397e1
Merge branch 'main' into digest-generic-mt
tessico Jan 18, 2023
abc72a7
constrain M::NodeValue to be of type PrimeField
tessico Jan 19, 2023
d3560a6
position should be of type `Variable`, not `usize`
tessico Jan 19, 2023
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49 changes: 45 additions & 4 deletions primitives/src/circuit/merkle_tree/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,12 +10,15 @@ use crate::{
merkle_tree::{MerkleTreeScheme, UniversalMerkleTreeScheme},
rescue::RescueParameter,
};
use ark_ff::PrimeField;
use jf_relation::{errors::CircuitError, BoolVar, Circuit, PlonkCircuit, Variable};

mod rescue_merkle_tree;
mod sparse_merkle_tree;
use ark_std::vec::Vec;

use super::rescue::RescueNativeGadget;

/// Gadget for a Merkle tree
///
/// # Examples
Expand Down Expand Up @@ -60,12 +63,16 @@ use ark_std::vec::Vec;
pub trait MerkleTreeGadget<M>
where
M: MerkleTreeScheme,
M::NodeValue: PrimeField,
{
/// Type to represent the merkle proof of the concrete MT instantiation.
/// It is MT-specific, e.g arity will affect the exact definition of the
/// underlying Merkle path.
type MembershipProofVar;

/// Gadget for the digest algorithm.
type DigestGadget: DigestAlgorithmGadget<M::NodeValue>;

/// Allocate a variable for the membership proof.
fn create_membership_proof_variable(
&mut self,
Expand Down Expand Up @@ -149,6 +156,7 @@ where
pub trait UniversalMerkleTreeGadget<M>: MerkleTreeGadget<M>
where
M: UniversalMerkleTreeScheme,
M::NodeValue: PrimeField,
{
/// Type to represent the merkle non-membership proof of the concrete MT
/// instantiation. It is MT-specific, e.g arity will affect the exact
Expand Down Expand Up @@ -212,13 +220,13 @@ fn constrain_sibling_order<F: RescueParameter>(
/// Circuit variable for a node in the Merkle path.
pub struct Merkle3AryNodeVar {
/// First sibling of the node.
pub sibling1: Variable,
sibling1: Variable,
/// Second sibling of the node.
pub sibling2: Variable,
sibling2: Variable,
/// Boolean variable indicating whether the node is a left child.
pub is_left_child: BoolVar,
is_left_child: BoolVar,
/// Boolean variable indicating whether the node is a right child.
pub is_right_child: BoolVar,
is_right_child: BoolVar,
}

/// Circuit variable for a Merkle non-membership proof of a 3-ary Merkle tree.
Expand All @@ -240,3 +248,36 @@ pub struct Merkle3AryMembershipProofVar {
node_vars: Vec<Merkle3AryNodeVar>,
elem_var: Variable,
}
/// Circuit counterpart to DigestAlgorithm
pub trait DigestAlgorithmGadget<F>
where
F: PrimeField,
{
/// Digest a list of variables
fn digest(circuit: &mut PlonkCircuit<F>, data: &[Variable]) -> Result<Variable, CircuitError>;

/// Digest an indexed element
fn digest_leaf(
circuit: &mut PlonkCircuit<F>,
pos: usize,
elem: Variable,
) -> Result<Variable, CircuitError>;
}

/// Digest gadget using for the Rescue hash function.
pub struct RescueDigestGadget {}

impl<F: RescueParameter> DigestAlgorithmGadget<F> for RescueDigestGadget {
fn digest(circuit: &mut PlonkCircuit<F>, data: &[Variable]) -> Result<Variable, CircuitError> {
Ok(RescueNativeGadget::<F>::rescue_sponge_no_padding(circuit, data, 1)?[0])
}

fn digest_leaf(
circuit: &mut PlonkCircuit<F>,
pos: Variable,
elem: Variable,
) -> Result<Variable, CircuitError> {
let zero = circuit.zero();
Ok(RescueNativeGadget::<F>::rescue_sponge_no_padding(circuit, &[zero, pos, elem], 1)?[0])
}
}
17 changes: 7 additions & 10 deletions primitives/src/circuit/merkle_tree/rescue_merkle_tree.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,21 +8,21 @@
//! with a Rescue hash function.

use crate::{
circuit::rescue::RescueNativeGadget,
circuit::merkle_tree::DigestAlgorithmGadget,
merkle_tree::{
internal::MerkleNode, prelude::RescueMerkleTree, MerkleTreeScheme, ToTraversalPath,
},
rescue::RescueParameter,
};
use ark_std::{string::ToString, vec::Vec};
use jf_relation::{errors::CircuitError, BoolVar, Circuit, PlonkCircuit, Variable};

type NodeVal<F> = <RescueMerkleTree<F> as MerkleTreeScheme>::NodeValue;
type MembershipProof<F> = <RescueMerkleTree<F> as MerkleTreeScheme>::MembershipProof;
use typenum::U3;

use super::{
constrain_sibling_order, Merkle3AryMembershipProofVar, Merkle3AryNodeVar, MerkleTreeGadget,
RescueDigestGadget,
};

impl<F> MerkleTreeGadget<RescueMerkleTree<F>> for PlonkCircuit<F>
Expand All @@ -31,6 +31,8 @@ where
{
type MembershipProofVar = Merkle3AryMembershipProofVar;

type DigestGadget = RescueDigestGadget;

fn create_membership_proof_variable(
&mut self,
merkle_proof: &MembershipProof<F>,
Expand Down Expand Up @@ -96,14 +98,10 @@ where
) -> Result<BoolVar, CircuitError> {
let computed_root_var = {
let proof_var = &proof_var;
let zero_var = self.zero();

// elem label = H(0, uid, elem)
let mut cur_label = RescueNativeGadget::<F>::rescue_sponge_no_padding(
self,
&[zero_var, elem_idx_var, proof_var.elem_var],
1,
)?[0];
let mut cur_label =
Self::DigestGadget::digest_leaf(self, elem_idx_var, proof_var.elem_var)?;
for cur_node in proof_var.node_vars.iter() {
let input_labels = constrain_sibling_order(
self,
Expand All @@ -115,8 +113,7 @@ where
)?;
// check that the left child's label is non-zero
self.non_zero_gate(input_labels[0])?;
cur_label =
RescueNativeGadget::<F>::rescue_sponge_no_padding(self, &input_labels, 1)?[0];
cur_label = Self::DigestGadget::digest(self, &input_labels)?;
}
Ok(cur_label)
}?;
Expand Down
22 changes: 9 additions & 13 deletions primitives/src/circuit/merkle_tree/sparse_merkle_tree.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
//! with a Rescue hash function.

use crate::{
circuit::rescue::RescueNativeGadget,
circuit::merkle_tree::DigestAlgorithmGadget,
merkle_tree::{
internal::MerkleNode, prelude::RescueSparseMerkleTree, MerkleTreeScheme, ToTraversalPath,
},
Expand All @@ -18,15 +18,15 @@ use ark_std::{string::ToString, vec::Vec};
use jf_relation::{errors::CircuitError, BoolVar, Circuit, PlonkCircuit, Variable};

type SparseMerkleTree<F> = RescueSparseMerkleTree<BigUint, F>;

type NodeVal<F> = <SparseMerkleTree<F> as MerkleTreeScheme>::NodeValue;
type MembershipProof<F> = <SparseMerkleTree<F> as MerkleTreeScheme>::MembershipProof;
use num_bigint::BigUint;
use typenum::U3;

use super::{
constrain_sibling_order, Merkle3AryMembershipProofVar, Merkle3AryNodeVar,
Merkle3AryNonMembershipProofVar, MerkleTreeGadget, UniversalMerkleTreeGadget,
Merkle3AryNonMembershipProofVar, MerkleTreeGadget, RescueDigestGadget,
UniversalMerkleTreeGadget,
};

impl<F> UniversalMerkleTreeGadget<SparseMerkleTree<F>> for PlonkCircuit<F>
Expand Down Expand Up @@ -57,8 +57,7 @@ where
)?;
// check that the left child's label is non-zero
self.non_zero_gate(input_labels[0])?;
cur_label =
RescueNativeGadget::<F>::rescue_sponge_no_padding(self, &input_labels, 1)?[0];
cur_label = Self::DigestGadget::digest(self, &input_labels)?;
}
Ok(cur_label)
}?;
Expand Down Expand Up @@ -126,6 +125,8 @@ where
{
type MembershipProofVar = Merkle3AryMembershipProofVar;

type DigestGadget = RescueDigestGadget;

fn create_membership_proof_variable(
&mut self,
merkle_proof: &MembershipProof<F>,
Expand Down Expand Up @@ -191,14 +192,10 @@ where
) -> Result<BoolVar, CircuitError> {
let computed_root_var = {
let proof_var = &proof_var;
let zero_var = self.zero();

// elem label = H(0, uid, elem)
let mut cur_label = RescueNativeGadget::<F>::rescue_sponge_no_padding(
self,
&[zero_var, elem_idx_var, proof_var.elem_var],
1,
)?[0];
let mut cur_label =
Self::DigestGadget::digest_leaf(self, elem_idx_var, proof_var.elem_var)?;
for cur_node in proof_var.node_vars.iter() {
let input_labels = constrain_sibling_order(
self,
Expand All @@ -210,8 +207,7 @@ where
)?;
// check that the left child's label is non-zero
self.non_zero_gate(input_labels[0])?;
cur_label =
RescueNativeGadget::<F>::rescue_sponge_no_padding(self, &input_labels, 1)?[0];
cur_label = Self::DigestGadget::digest(self, &input_labels)?;
}
Ok(cur_label)
}?;
Expand Down