AntiPatternViewOnEncrypted

Category: Basic | Difficulty: Intermediate | Chapters: Anti Patterns | Concept: View functions return encrypted handles, not plaintext

Demonstrates why a view call still returns encrypted handles.

Why this example

This example focuses on View functions return encrypted handles, not plaintext. It is designed to be self-contained and easy to run locally.

Quick start

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

Dependencies

None

Contract and test

AntiPatternViewOnEncrypted.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 AntiPatternViewOnEncrypted
 * @author Gustavo Valverde
 * @notice Demonstrates why a view call still returns encrypted handles.
 * @dev Example for fhEVM Examples - Basic Category
 *
 * @custom:category basic
 * @custom:chapter anti-patterns
 * @custom:concept View functions return encrypted handles, not plaintext
 * @custom:difficulty intermediate
 */
contract AntiPatternViewOnEncrypted is ZamaEthereumConfig {
    mapping(address user => euint64 value) private storedValues;

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

    /// @notice Read the encrypted value from a view function.
    /// @dev The return value is still encrypted and must be decrypted off-chain.
    /// @param user Account holding the encrypted value
    /// @return The encrypted value handle
    function getEncryptedValue(address user) external view returns (euint64) {
        return storedValues[user];
    }
}

AntiPatternViewOnEncrypted.test.ts

Pitfalls to avoid

• returns an encrypted handle even in a view call

API Reference

Overview

Demonstrates why a view call still returns encrypted handles.

Developer Notes

Example for fhEVM Examples - Basic Category

storeValue

function storeValue(externalEuint64 encValue, bytes inputProof) external

Store an encrypted value.

Parameters

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

getEncryptedValue

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

Read the encrypted value from a view function.

The return value is still encrypted and must be decrypted off-chain.

Parameters

Name	Type	Description
user	address	Account holding the encrypted value

Return Values

Name	Type	Description
[0]	euint64	The encrypted value handle