PedersonsCommitment.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract PedersonsCommitment {
    struct Commitment {
        bytes32 commitmentValue;
        bool isSet;
    }

    mapping(uint256 => Commitment) public commitments;
    bytes32 public root;

    modifier rootIsSet() {
        require(root != bytes32(0), "Root not set");
        _;
    }

    function commitToNumber(uint256 index, bytes32 commitmentValue) public {
        commitments[index] = Commitment(commitmentValue, true);
    }

    function setRoot(bytes32 newRoot) public {
        root = newRoot;
    }

    function verifyDuplicate(uint256[] memory indices, bytes32[] memory proof) public view rootIsSet returns (bool) {
        require(indices.length > 0, "Indices array is empty");
        require(proof.length > 0, "Proof array is empty");

        bytes32 computedRoot = root;

        for (uint256 i = 0; i < indices.length; i++) {
            uint256 index = indices[i];
            Commitment storage commitment = commitments[index];
            require(commitment.isSet, "Commitment not set");

            bytes32 commitmentValue = commitment.commitmentValue;
            bytes32 proofElement = proof[i];

            if (i % 2 == 0) {
                computedRoot = keccak256(abi.encodePacked(computedRoot, proofElement));
            } else {
                computedRoot = keccak256(abi.encodePacked(proofElement, computedRoot));
            }
        }

        return computedRoot == commitmentValue; // Compare the computed root with the provided commitment value
    }
}