lssa/node_core/src/executions/de.rs

use k256::Scalar;
use secp256k1_zkp::{compute_adaptive_blinding_factor, verify_commitments_sum_to_equal, CommitmentSecrets, Generator, PedersenCommitment, Tag, Tweak, SECP256K1};
use rand::thread_rng;
use sha2::{Digest, Sha256};
use serde::{Serialize, Deserialize};
use storage::{commitment::Commitment, commitments_sparse_merkle_tree::CommitmentsSparseMerkleTree, nullifier::UTXONullifier, nullifier_sparse_merkle_tree::NullifierSparseMerkleTree};
use utxo::{
    utxo_core::{UTXOPayload, UTXO},
    utxo_tree::UTXOSparseMerkleTree,
};
use monotree::hasher::Blake3;
use monotree::{Hasher, Monotree, Proof};
use bincode;

fn commitment_secrets_random(value: u64) -> CommitmentSecrets {
    CommitmentSecrets {
        value,
        value_blinding_factor: Tweak::new(&mut thread_rng()),
        generator_blinding_factor: Tweak::new(&mut thread_rng()),
    }
}

pub fn tag_random() -> Tag {
    use rand::thread_rng;
    use rand::RngCore;

    let mut bytes = [0u8; 32];
    thread_rng().fill_bytes(&mut bytes);

    Tag::from(bytes)
}

pub fn commit(comm: &CommitmentSecrets, tag: Tag) -> PedersenCommitment {
    let generator = Generator::new_blinded(SECP256K1, tag, comm.generator_blinding_factor);

    PedersenCommitment::new(SECP256K1, comm.value, comm.value_blinding_factor, generator)
}

// Hash function placeholder (replace with your cryptographic library's hash).
fn hash(input: &[u8]) -> Vec<u8> {
    Sha256::digest(input).to_vec()
}

// Generate nullifiers

// takes the input_utxo and nsk 
// returns the nullifiers[i], where the nullifier[i] = hash(in_commitments[i] || nsk) where the hash function
pub fn generate_nullifiers(input_utxo: &UTXO, nsk: &[u8]) -> Vec<u8> {
    let mut input = bincode::serialize(input_utxo).unwrap().to_vec();
    input.extend_from_slice(nsk);
    hash(&input)
}

// Generate commitments for output UTXOs

//  uses the list of input_utxos[] 
//  returns in_commitments[] where each in_commitments[i] = Commitment(in_utxos[i]) where the commitment 
pub fn generate_commitments(input_utxos: &[UTXO]) -> Vec<Vec<u8>> {
    input_utxos
        .iter()
        .map(|utxo| {
            let serialized = bincode::serialize(utxo).unwrap(); // Serialize UTXO.
            hash(&serialized)
        })
        .collect()
}

// Validate inclusion proof for in_commitments

// takes the in_commitments[i] as a leaf, the root hash root_commitment and the path in_commitments_proofs[i][], 
// returns True if the in_commitments[i] is in the tree with root hash root_commitment otherwise returns False, as membership proof.
pub fn validate_in_commitments_proof(
    in_commitment: &Vec<u8>,
    root_commitment: Vec<u8>,
    in_commitments_proof: &[Vec<u8>],
) -> bool {
    // Placeholder implementation.
    // Replace with Merkle proof verification logic.
    // hash(&[pedersen_commitment.serialize().to_vec(), in_commitments_proof.concat()].concat()) == root_commitment

    let mut nsmt = CommitmentsSparseMerkleTree {
        curr_root: Option::Some(root_commitment),
        tree: Monotree::default(),
        hasher: Blake3::new(),
    };

    let commitments: Vec<_> = in_commitments_proof.into_iter().map(|n_p| Commitment { commitment_hash: n_p.clone() }).collect();
    nsmt.insert_items(commitments).unwrap();


    nsmt.get_non_membership_proof(in_commitment.clone()).unwrap().1.is_some()
}

// Validate non-membership proof for nullifiers

// takes the nullifiers[i], path nullifiers_proof[i][] and the root hash root_nullifier, 
// returns True if the nullifiers[i] is not in the tree with root hash root_nullifier otherwise returns False, as non-membership proof.
pub fn validate_nullifiers_proof(
    nullifier: [u8; 32],
    root_nullifier: [u8; 32],
    nullifiers_proof: &[[u8; 32]],
) -> bool {
    let mut nsmt = NullifierSparseMerkleTree {
        curr_root: Option::Some(root_nullifier),
        tree: Monotree::default(),
        hasher: Blake3::new(),
    };

    let nullifiers: Vec<_> = nullifiers_proof.into_iter().map(|n_p| UTXONullifier { utxo_hash: *n_p }).collect();
    nsmt.insert_items(nullifiers).unwrap();


    nsmt.get_non_membership_proof(nullifier).unwrap().1.is_none()
}