ChainStar

Problem Statement

CoStar on Blockchain is a decentralized astrology platform that combines celestial insights with blockchain-powered privacy. Users can input their birth details securely, and the data is encrypted and stored on-chain using smart contracts — ensuring full ownership and transparency. Astrologers and algorithms then generate personalized daily horoscopes and compatibility reports without compromising user privacy. The platform also supports token-based interactions, where users can tip astrologers or unlock premium charts.

Solution

The project uses Ethereum smart contracts (Solidity) to handle encrypted user birth data and astrology requests. We built the backend with Node.js and Express, connecting to a MongoDB database for metadata while storing sensitive data hashes on-chain. The frontend is designed in React with Ethers.js for wallet interactions (MetaMask). Astrological computations are powered by the Swiss Ephemeris API, while encryption and decryption are handled using AES-256. Our biggest challenge was maintaining data privacy in a public blockchain — solved by combining off-chain storage with on-chain proofs. The result is a user-owned, censorship-resistant astrology experience.