FHE2P

Screenshots

Problem Statement

MA DescriptionGo in as much detail as you can about what this project is. Please be as clear as possible!This project, named FHE2P (Fully Homomorphic Encryption Peer-to-Peer), is a decentralized voucher marketplace implemented as a smart contract on a blockchain that supports Fully Homomorphic Encryption (FHE). Here's a detailed description of the project:Core Concept: It allows for the creation, sale, resale, and redemption of encrypted vouchers. The system uses FHE to maintain privacy and security of sensitive voucher data. Key Features: Voucher Creation: Administrators can create vouchers with encrypted codes and PINs. Buying and Reselling: Users can purchase vouchers directly or buy resold vouchers. Voucher Revelation: Owners can reveal their vouchers using a PIN. Metadata Retrieval: Public voucher information can be accessed without revealing private data. Privacy and Security: Voucher codes and PINs are stored in encrypted form. FHE allows for computations on encrypted data without decryption. Only the rightful owner can reveal a voucher's contents. Economic Model: Platform fees are applied to resold vouchers. Stablecoin integration for payments. Voucher Structure: Each voucher contains: Encrypted code and PIN Price Expiry date Owner and seller information Public metadata (image URL, description) User Interactions: Buying: Users can purchase available vouchers. Reselling: Owners can resell their unrevealed vouchers. Revealing: Owners can reveal their vouchers using the correct PIN. Viewing: Users can view available vouchers and their own purchased vouchers. Administrative Functions: Voucher listing Platform fee adjustment Emergency controls (pausing, fund withdrawal) Technical Implementation: Uses Solidity with FHE extensions. Integrates OpenZeppelin libraries for standard functionalities. Implements custom FHE operations for encrypted data handling. Use Cases: Gift card marketplaces Ticket reselling platforms Confidential coupon systems This project aims to create a secure, private, and flexible system for voucher trading, leveraging blockchain technology and advanced cryptography to ensure user privacy and data security while maintaining the functionality of a dynamic marketplace.

Solution

This FHE2P (Fully Homomorphic Encryption Peer-to-Peer) project was built using a combination of cutting-edge blockchain technologies and cryptographic techniques. Here's a detailed breakdown of how it was made:Core Technology Stack:Solidity (v0.8.20): The primary smart contract language.Fhenix Protocol: Leveraged for Fully Homomorphic Encryption capabilities.OpenZeppelin Contracts: Used for standard, secure implementations of common contract functionality.FHE Integration:Imported "@fhenixprotocol/contracts/FHE.sol" to access FHE operations.Utilized encrypted types like euint256, euint32, ebool, and eaddress for sensitive data.Implemented FHE operations (e.g., FHE.eq, FHE.lt, FHE.add) for computations on encrypted data.Voucher Structure:Designed a Voucher struct combining encrypted and public fields.Used euint256 for encrypted voucher codes and euint64 for PINs.Stored public metadata (price, expiry date, image URL, description) for easy retrieval.Smart Contract Architecture:Inherited from OpenZeppelin's Ownable, Pausable, and ReentrancyGuard for security.Implemented SafeERC20 for secure token transfers.Created a mapping of voucher IDs to Voucher structs for efficient storage and retrieval.Key Functionalities:Voucher Listing: Admins can list vouchers with encrypted and public data.Buying Mechanism: Implemented separate functions for buying new and resold vouchers.Reselling: Allows users to resell their unrevealed vouchers.Revelation: Users can reveal vouchers using encrypted PINs.Privacy-Preserving Features:Used FHE.sealoutput for secure revelation of voucher codes.Implemented encrypted comparisons for expiry checks and ownership verification.Metadata Handling:Created a separate VoucherMetaData struct for public information.Implemented functions to retrieve metadata for available vouchers and user-owned vouchers.Economic Model:Integrated a platform fee system for resold vouchers.Used SafeERC20 for secure stablecoin transfers.Security Measures:Implemented pause functionality for emergency situations.Added nonReentrant modifiers to prevent reentrancy attacks.Used require statements and FHE.req for validation checks.Optimization Techniques:Two-pass approach in metadata retrieval functions to optimize gas usage.Used uint32 for prices and expiry dates to save storage space.Notable "Hacky" Solutions:Used FHE.decrypt within view functions to check encrypted conditions, allowing for gas-efficient queries of encrypted data.Implemented a custom approach to handle encrypted booleans (ebool) in conditional logic.Partner Technologies:Fhenix Protocol: Enabled FHE operations, significantly enhancing the privacy and security of the system.OpenZeppelin: Provided battle-tested implementations of common contract patterns, improving security and reducing development time.Testing and Deployment:Developed on a local blockchain environment supporting FHE operations.Planned for deployment on Fhenix's testnet for real-world testing.This project demonstrates a novel approach to building a privacy-preserving marketplace by leveraging FHE in smart contracts. The combination of blockchain technology and advanced cryptography allows for a secure, private, yet transparent system for voucher trading.