Add support for anchoring with an ERC20 contract with deposit and withdraw

solidity/contracts/erc20.sol

@@ -0,0 +1,40 @@
+// Copyright © 2024 Kaleido, Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+pragma solidity ^0.8.20;
+
+import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
+import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import "hardhat/console.sol";
+
+/// @title A sample implementation of a Zeto based fungible token with anonymity and no encryption
+/// @author Kaleido, Inc.
+/// @dev The proof has the following statements:
+///        - each value in the output commitments must be a positive number in the range 0 ~ (2^40 - 1)
+///        - the sum of the input values match the sum of output values
+///        - the hashes in the input and output match the `hash(value, salt, owner public key)` formula
+///        - the sender possesses the private BabyJubjub key, whose public key is part of the pre-image of the input commitment hashes
+contract SampleERC20 is ERC20, Ownable {
+    constructor()
+        ERC20("Sample ERC20 token", "SampleERC20")
+        Ownable(msg.sender)
+    {
+        _mint(msg.sender, 1000000 * 10 ** 18);
+    }
+
+    function mint(address to, uint256 amount) public onlyOwner {
+        _mint(to, amount);
+    }
+}

solidity/contracts/lib/verifier_check_hashes_value.sol

@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-3.0
+/*
+    Copyright 2021 0KIMS association.
+
+    This file is generated with [snarkJS](https://github.com/iden3/snarkjs).
+
+    snarkJS is a free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    snarkJS is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+    License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with snarkJS. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+pragma solidity >=0.7.0 <0.9.0;
+
+contract Groth16Verifier_CheckValue {
+    // Scalar field size
+    uint256 constant r    = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
+    // Base field size
+    uint256 constant q   = 21888242871839275222246405745257275088696311157297823662689037894645226208583;
+
+    // Verification Key data
+    uint256 constant alphax  = 20491192805390485299153009773594534940189261866228447918068658471970481763042;
+    uint256 constant alphay  = 9383485363053290200918347156157836566562967994039712273449902621266178545958;
+    uint256 constant betax1  = 4252822878758300859123897981450591353533073413197771768651442665752259397132;
+    uint256 constant betax2  = 6375614351688725206403948262868962793625744043794305715222011528459656738731;
+    uint256 constant betay1  = 21847035105528745403288232691147584728191162732299865338377159692350059136679;
+    uint256 constant betay2  = 10505242626370262277552901082094356697409835680220590971873171140371331206856;
+    uint256 constant gammax1 = 11559732032986387107991004021392285783925812861821192530917403151452391805634;
+    uint256 constant gammax2 = 10857046999023057135944570762232829481370756359578518086990519993285655852781;
+    uint256 constant gammay1 = 4082367875863433681332203403145435568316851327593401208105741076214120093531;
+    uint256 constant gammay2 = 8495653923123431417604973247489272438418190587263600148770280649306958101930;
+    uint256 constant deltax1 = 11559732032986387107991004021392285783925812861821192530917403151452391805634;
+    uint256 constant deltax2 = 10857046999023057135944570762232829481370756359578518086990519993285655852781;
+    uint256 constant deltay1 = 4082367875863433681332203403145435568316851327593401208105741076214120093531;
+    uint256 constant deltay2 = 8495653923123431417604973247489272438418190587263600148770280649306958101930;
+
+
+    uint256 constant IC0x = 21353820865548503329577756525221633465332622166799959856825877352905192473267;
+    uint256 constant IC0y = 156932616567894649841337587302503574238981053813007972854040490364635182694;
+
+    uint256 constant IC1x = 12322194858529188061062625971813098256741654889417169683222060161781584608609;
+    uint256 constant IC1y = 20246326882683168066748851145817053112674664250127727211412715232179245157022;
+
+    uint256 constant IC2x = 8022016804019415581152964105487657307044363981768180695730643477130121229579;
+    uint256 constant IC2y = 15328789577726767026198857145765587783001722435319756601432638671812565154978;
+
+
+    // Memory data
+    uint16 constant pVk = 0;
+    uint16 constant pPairing = 128;
+
+    uint16 constant pLastMem = 896;
+
+    function verifyProof(uint[2] calldata _pA, uint[2][2] calldata _pB, uint[2] calldata _pC, uint[2] calldata _pubSignals) public view returns (bool) {
+        assembly {
+            function checkField(v) {
+                if iszero(lt(v, q)) {
+                    mstore(0, 0)
+                    return(0, 0x20)
+                }
+            }
+
+            // G1 function to multiply a G1 value(x,y) to value in an address
+            function g1_mulAccC(pR, x, y, s) {
+                let success
+                let mIn := mload(0x40)
+                mstore(mIn, x)
+                mstore(add(mIn, 32), y)
+                mstore(add(mIn, 64), s)
+
+                success := staticcall(sub(gas(), 2000), 7, mIn, 96, mIn, 64)
+
+                if iszero(success) {
+                    mstore(0, 0)
+                    return(0, 0x20)
+                }
+
+                mstore(add(mIn, 64), mload(pR))
+                mstore(add(mIn, 96), mload(add(pR, 32)))
+
+                success := staticcall(sub(gas(), 2000), 6, mIn, 128, pR, 64)
+
+                if iszero(success) {
+                    mstore(0, 0)
+                    return(0, 0x20)
+                }
+            }
+
+            function checkPairing(pA, pB, pC, pubSignals, pMem) -> isOk {
+                let _pPairing := add(pMem, pPairing)
+                let _pVk := add(pMem, pVk)
+
+                mstore(_pVk, IC0x)
+                mstore(add(_pVk, 32), IC0y)
+
+                // Compute the linear combination vk_x
+
+                g1_mulAccC(_pVk, IC1x, IC1y, calldataload(add(pubSignals, 0)))
+
+                g1_mulAccC(_pVk, IC2x, IC2y, calldataload(add(pubSignals, 32)))
+
+
+                // -A
+                mstore(_pPairing, calldataload(pA))
+                mstore(add(_pPairing, 32), mod(sub(q, calldataload(add(pA, 32))), q))
+
+                // B
+                mstore(add(_pPairing, 64), calldataload(pB))
+                mstore(add(_pPairing, 96), calldataload(add(pB, 32)))
+                mstore(add(_pPairing, 128), calldataload(add(pB, 64)))
+                mstore(add(_pPairing, 160), calldataload(add(pB, 96)))
+
+                // alpha1
+                mstore(add(_pPairing, 192), alphax)
+                mstore(add(_pPairing, 224), alphay)
+
+                // beta2
+                mstore(add(_pPairing, 256), betax1)
+                mstore(add(_pPairing, 288), betax2)
+                mstore(add(_pPairing, 320), betay1)
+                mstore(add(_pPairing, 352), betay2)
+
+                // vk_x
+                mstore(add(_pPairing, 384), mload(add(pMem, pVk)))
+                mstore(add(_pPairing, 416), mload(add(pMem, add(pVk, 32))))
+
+
+                // gamma2
+                mstore(add(_pPairing, 448), gammax1)
+                mstore(add(_pPairing, 480), gammax2)
+                mstore(add(_pPairing, 512), gammay1)
+                mstore(add(_pPairing, 544), gammay2)
+
+                // C
+                mstore(add(_pPairing, 576), calldataload(pC))
+                mstore(add(_pPairing, 608), calldataload(add(pC, 32)))
+
+                // delta2
+                mstore(add(_pPairing, 640), deltax1)
+                mstore(add(_pPairing, 672), deltax2)
+                mstore(add(_pPairing, 704), deltay1)
+                mstore(add(_pPairing, 736), deltay2)
+
+
+                let success := staticcall(sub(gas(), 2000), 8, _pPairing, 768, _pPairing, 0x20)
+
+                isOk := and(success, mload(_pPairing))
+            }
+
+            let pMem := mload(0x40)
+            mstore(0x40, add(pMem, pLastMem))
+
+            // Validate that all evaluations ∈ F
+
+            checkField(calldataload(add(_pubSignals, 0)))
+
+            checkField(calldataload(add(_pubSignals, 32)))
+
+            checkField(calldataload(add(_pubSignals, 64)))
+
+
+            // Validate all evaluations
+            let isValid := checkPairing(_pA, _pB, _pC, _pubSignals, pMem)
+
+            mstore(0, isValid)
+             return(0, 0x20)
+         }
+     }
+ }