Verifit: Blockchain-Powered Fitness Verification and Incentivization

Verifit is an innovative fitness application that leverages blockchain technology, zero-knowledge proofs, and smart contracts to create a trustless, privacy-preserving ecosystem for fitness tracking and goal achievement.

Core Components

1. User Authentication

   • Users log in to the Verifit app using their Google accounts, ensuring a seamless and secure authentication process.

2. Data Retrieval with zkFetch

   • Verifit utilizes a custom tool called zkFetch to retrieve user fitness data from the Google Fitness API.
   • zkFetch is similar to the standard fetch API but with a crucial difference: it returns not only the requested data but also a verifiable zero-knowledge proof.
   • This proof allows for the validation of the data's authenticity without revealing the actual data, preserving user privacy.

3. On-Chain Attestation

   • Users can attest to their fitness data using the Sign Protocol.
   • This attestation process stores a cryptographic commitment of the data on the blockchain, creating an immutable record of the user's fitness activities.

4. Smart Contract Integration

   • A hook contract is triggered during the attestation process.
   • This contract verifies the zero-knowledge proof provided by zkFetch, ensuring the data's validity.

5. NFT Minting

   • Upon successful verification, the system mints a non-fungible token (NFT) for the user.
   • The NFT contains key fitness data such as the number of steps taken and the start and end timestamps of the activity period.
   • These NFTs serve as blockchain-based certificates of achievement, providing users with tangible, tradeable proof of their fitness accomplishments.

6. Accountability Bets

   • Verifit introduces a novel feature called "Accountability Bets" through the CreateBets smart contract.
   • Users can create fitness goals and place bets on their ability to achieve these goals.
   • Other users can participate in these bets, creating a community-driven incentive system for fitness achievement.

7. Bet Resolution

   • When it's time to resolve a bet, Verifit again uses zkFetch to retrieve the relevant fitness data and associated proof.
   • The CreateBets contract verifies this proof and automatically resolves the bet based on the achieved results.
   • This process ensures fair and transparent bet resolution without compromising user privacy.

Key Benefits

1. Privacy Preservation: By using zero-knowledge proofs, Verifit allows users to verify their fitness achievements without revealing sensitive data.

2. Trustless Verification: The use of blockchain and smart contracts eliminates the need for a trusted third party to verify fitness data or resolve bets.

3. Gamification and Incentivization: The combination of NFT rewards and accountability bets creates strong motivators for users to achieve their fitness goals.

4. Immutable Record Keeping: All verified achievements and bet resolutions are recorded on the blockchain, providing an tamper-proof history of user accomplishments.

5. Community Building: The betting system encourages users to engage with each other, fostering a supportive and competitive fitness community.

Technical Innovation

Verifit stands out for its novel application of zero-knowledge proofs in the fitness tracking domain. By combining zkFetch with blockchain technology, it creates a unique solution that addresses both data privacy and verifiability concerns in fitness tracking applications.

The project demonstrates how advanced cryptographic techniques can be applied to real-world problems, potentially paving the way for similar privacy-preserving solutions in other domains where data verification is crucial but privacy is a concern.

User: Initiates the process by logging in. Google Authentication: Handles user login. Verifit App: The main application interface. zkFetch: A tool similar to fetch that returns data with a verifiable ZK proof. Fitness API: Provides the user's fitness data. Sign Protocol: Used for attesting the ZK proof. Blockchain: Stores attestations, NFTs, and bet data. Hook Contract: Checks proof verifiability. Proof Verification: Verifies the ZK proof. Mint NFT: Creates an NFT with steps count and timestamps. CreateBets Contract: Manages accountability bets. Envio:An indexer to query bets