InputProofsExplained

Category: Basic | Difficulty: Intermediate | Chapters: Input Proofs | Concept: Input proofs bind encrypted inputs to a contract and sender

Demonstrate input proof binding to contract and signer.

Why this example

This example focuses on Input proofs bind encrypted inputs to a contract and sender. It is designed to be self-contained and easy to run locally.

Quick start

npm install
npm run test:mocked -- test/basic/InputProofsExplained.test.ts

Dependencies

None

Contract and test

InputProofsExplained.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.27;

import {FHE, euint64, externalEuint64} from "@fhevm/solidity/lib/FHE.sol";
import {ZamaEthereumConfig} from "@fhevm/solidity/config/ZamaConfig.sol";

/**
 * @title InputProofsExplained
 * @author Gustavo Valverde
 * @notice Demonstrate input proof binding to contract and signer.
 * @dev Example for fhEVM Examples - Basic Category
 *
 * @custom:category basic
 * @custom:chapter input-proofs
 * @custom:concept Input proofs bind encrypted inputs to a contract and sender
 * @custom:difficulty intermediate
 */
contract InputProofsExplained is ZamaEthereumConfig {
    mapping(address user => euint64 secret) private secrets;

    /// @notice Store an encrypted secret for the sender.
    /// @param encValue Encrypted value handle
    /// @param inputProof Proof for the encrypted input
    function storeSecret(externalEuint64 encValue, bytes calldata inputProof) external {
        euint64 value = FHE.fromExternal(encValue, inputProof);
        secrets[msg.sender] = value;
        FHE.allowThis(value);
        FHE.allow(value, msg.sender);
    }

    /// @notice Retrieve the encrypted secret for a user.
    /// @param user Account holding the encrypted secret
    /// @return The encrypted secret value
    function getSecret(address user) external view returns (euint64) {
        return secrets[user];
    }
}

InputProofsExplained.test.ts

Pitfalls to avoid

• rejects a proof bound to a different sender

• rejects a proof bound to a different contract

API Reference

Overview

Demonstrate input proof binding to contract and signer.

Developer Notes

Example for fhEVM Examples - Basic Category

storeSecret

function storeSecret(externalEuint64 encValue, bytes inputProof) external

Store an encrypted secret for the sender.

Parameters

Name	Type	Description
encValue	externalEuint64	Encrypted value handle
inputProof	bytes	Proof for the encrypted input

getSecret

function getSecret(address user) external view returns (euint64)

Retrieve the encrypted secret for a user.

Parameters

Name	Type	Description
user	address	Account holding the encrypted secret

Return Values

Name	Type	Description
[0]	euint64	The encrypted secret value