PoC: onchain rln tree + root

contracts/Rln.sol

@@ -3,7 +3,7 @@ pragma solidity 0.8.15;
 
 import "./RlnBase.sol";
 
-contract Rln is RlnBase {
+contract RLN is RlnBase {
     constructor(uint256 membershipDeposit, uint256 depth, address _poseidonHasher, address _verifier)
         RlnBase(membershipDeposit, depth, _poseidonHasher, _verifier)
     {}

contracts/RlnBase.sol

@@ -4,6 +4,7 @@ pragma solidity 0.8.15;
 
 import {PoseidonHasher} from "./PoseidonHasher.sol";
 import {IVerifier} from "./IVerifier.sol";
+import {BinaryIMT, BinaryIMTData} from "@zk-kit/imt.sol/BinaryIMT.sol";
 
 /// The tree is full
 error FullTree();
@@ -61,6 +62,7 @@ abstract contract RlnBase {
     /// maps from idCommitment to their index in the set
     mapping(uint256 => uint256) public members;
 
+    /// @notice The membership status of each member
     mapping(uint256 => bool) public memberExists;
 
     /// @notice The balance of each user that can be withdrawn
@@ -75,6 +77,9 @@ abstract contract RlnBase {
     /// @notice the deployed block number
     uint32 public immutable deployedBlockNumber;
 
+    /// @notice the Incremental Merkle Tree
+    BinaryIMTData public imtData;
+
     /// Emitted when a new member is added to the set
     /// @param idCommitment The idCommitment of the member
     /// @param index The index of the member in the set
@@ -97,6 +102,7 @@ abstract contract RlnBase {
         poseidonHasher = PoseidonHasher(_poseidonHasher);
         verifier = IVerifier(_verifier);
         deployedBlockNumber = uint32(block.number);
+        BinaryIMT.initWithDefaultZeroes(imtData, 20);
     }
 
     /// Allows a user to register as a member
@@ -118,6 +124,7 @@ abstract contract RlnBase {
 
         members[idCommitment] = idCommitmentIndex;
         memberExists[idCommitment] = true;
+        BinaryIMT.insert(imtData, idCommitment);
         stakedAmounts[idCommitment] = stake;
 
         emit MemberRegistered(idCommitment, idCommitmentIndex);
@@ -164,6 +171,7 @@ abstract contract RlnBase {
         members[idCommitment] = 0;
         memberExists[idCommitment] = false;
         stakedAmounts[idCommitment] = 0;
+        // TODO: remove from IMT
 
         // refund deposit
         withdrawalBalance[receiver] += amountToTransfer;
@@ -191,10 +199,10 @@ abstract contract RlnBase {
     }
 
     /// Hashes a value using the Poseidon hasher
-    /// NOTE: The variant of Poseidon we use accepts only 1 input, assume n=2, and the second input is 0
-    /// @param input The value to hash
-    function hash(uint256 input) internal view returns (uint256) {
-        return poseidonHasher.hash(input);
+    /// NOTE: The variant of Poseidon we use accepts only 1 input, assume n=2
+    /// @param inputs The values to hash
+    function hash(uint256[2] memory inputs) internal view returns (uint256) {
+        return poseidonHasher.hash(inputs);
     }
 
     function isValidCommitment(uint256 idCommitment) public view returns (bool) {
@@ -215,4 +223,8 @@ abstract contract RlnBase {
             [idCommitment, uint256(uint160(receiver))]
         );
     }
+
+    function computeRoot() external view returns (uint256) {
+        return imtData.root;
+    }
 }

deploy/001_deploy_poseidon_hasher.ts

@@ -7,9 +7,17 @@ const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
 
   const [deployer] = await getUnnamedAccounts();
 
+  const deployRes = await deploy("PoseidonT3", {
+    from: deployer,
+    log: true,
+  });
+
   await deploy("PoseidonHasher", {
     from: deployer,
     log: true,
+    libraries: {
+      PoseidonT3: deployRes.address,
+    },
   });
 };
 export default func;

deploy/003_deploy_rln.ts

@@ -11,12 +11,24 @@ const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
     .address;
   const rlnVerifierAddress = (await deployments.get("Verifier")).address;
 
-  await deploy("Rln", {
+  const deployRes = await deploy("BinaryIMT", {
+    from: deployer,
+    log: true,
+    libraries: {
+      PoseidonT3: (await deployments.get("PoseidonT3")).address,
+    },
+  });
+
+  await deploy("RLN", {
     from: deployer,
     log: true,
     args: [1000000000000000, 20, poseidonHasherAddress, rlnVerifierAddress],
+    libraries: {
+      BinaryIMT: deployRes.address,
+    },
   });
 };
+
 export default func;
 func.tags = ["Rln"];
-func.dependencies = ["PoseidonHasher", "RlnVerifier"];
+func.dependencies = ["PoseidonHasher", "RlnVerifier", "BinaryIMT"];