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Example Contract Before and After CoFHE

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

contract SimpleCounter {
address owner;
uint256 counter;

modifier onlyOwner() {
require(msg.sender == owner, "Only the owner can increment or decrement the counter");
_;
}

constructor(uint initial_value) {
owner = msg.sender;
counter = initial_value;
}

modifier onlyOwner() {
require(msg.sender == owner, "Only the owner can increment or decrement the counter");
_;
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {FHE, euint64, InEuint64} from "@fhenixprotocol/cofhe-contracts/FHE.sol";

contract SimpleCounter {
address owner;

euint64 counter;
euint64 lastDecryptedCounter;
euint64 step;

modifier onlyOwner() {
require(msg.sender == owner, "Only the owner can access that function");
_;
}

constructor(uint64 initial_value) {
owner = msg.sender;
counter = FHE.asEuint64(initial_value);
FHE.allowThis(counter);

// Encrypt the value 1 only once instead of every value change
step = FHE.asEuint64(1);
FHE.allowThis(step);
}

function increment_counter() external onlyOwner {
counter = FHE.add(counter, step);
FHE.allowThis(counter);
}

function decrement_counter() external onlyOwner {
counter = FHE.sub(counter, step);
FHE.allowThis(counter);
}

function decrypt_counter() external onlyOwner {
lastDecryptedCounter = counter;
FHE.decrypt(lastDecryptedCounter);
}

function get_counter_value() external view returns(uint256) {
(uint256 value, bool decrypted) = FHE.getDecryptResultSafe(lastDecryptedCounter);
if (!decrypted)
revert("Value is not ready");

return value;
}
}