Devra

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Devra - Decentralized Data Marketplace

Inspiration

The inspiration for Devra came from witnessing the challenges faced by AI researchers and data scientists in accessing quality datasets. Traditional data marketplaces are plagued with issues, centralized control, lack of transparency, questionable data provenance, and unfair compensation for data providers. We asked ourselves: What if we could create a trustless marketplace where data ownership is verifiable, quality is AI-verified, and transactions are transparent?

The rise of blockchain technology and the growing demand for ethical AI solutions converged into a single vision: democratize data trading while ensuring quality and authenticity using Polkadot.

What it does

Devra is a decentralized data marketplace built on Polkadot's Westend Asset Hub testnet that revolutionizes how datasets are bought, sold, and verified. Here's what makes it special:

NFT-Based Ownership: Every dataset is minted as an NFT, providing immutable proof of ownership and provenance
AI Verification: Our AI agent analyzes datasets for quality, completeness, and authenticity before they hit the marketplace
Encrypted Storage: Datasets are encrypted and stored on IPFS via crust network, ensuring decentralization and security
Smart Contract Trading: Trustless peer-to-peer transactions powered by Polkadot's Solidity smart contracts
Dynamic Pricing: Sellers can list, update prices, or cancel listings—all on-chain
Beautiful UX: A sleek, cyberpunk-inspired interface that makes blockchain feel accessible

The workflow is simple yet powerful: Upload → Seller uploads dataset and metadata Verify → AI agent validates data quality and authenticity Mint → Dataset becomes an NFT with encrypted IPFS storage List → Seller sets price and lists on marketplace Buy → Buyers purchase with WND tokens Access → Smart contract handles decryption and delivery

How we built it

Building Devra was a full-stack blockchain adventure that pushed us to master multiple technologies:

Frontend (Next.js 15 + React 19)

Modern React with Server Components and App Router
Framer Motion for smooth, eye-catching animations
Tailwind CSS v4 for rapid, responsive styling
Wagmi v2 + Viem for Ethereum wallet integration
Custom hooks for contract interactions (mint, list, buy, cancel)

Smart Contracts (Solidity)

ERC-721 NFT standard for dataset ownership
Integrated marketplace logic within the NFT contract
Events for tracking listings, sales, and cancellations
Secure price handling using OpenZeppelin libraries

Blockchain Integration

Deployed on Westend Asset Hub (Polkadot's EVM-compatible testnet)
Used Remix IDE for contract development and testing
MetaMask and Talisman wallet support
Transaction tracking via Blockscout explorer

AI Verification Pipeline

Python-based AI agent for dataset analysis
Checks for data quality metrics: ( Q = \frac{\text{valid_rows}}{\text{total_rows}} \times 100 )
Authenticity scoring using statistical analysis
Integration with backend API for verification results

Decentralized Storage

IPFS via Crust for storing encrypted datasets
Server-side encryption before upload
Decryption keys managed by Custom backend
Gateway fallbacks for reliable access

Architecture

┌─────────────┐
│   Frontend  │ (Next.js + Wagmi)
└──────┬──────┘
       │
┌──────▼──────────────────────┐
│  Smart Contract (Solidity)  │
│  - Mint NFT                 │
│  - List/Delist Dataset      │
│  - Buy/Transfer             │
└──────┬──────────────────────┘
       │
┌──────▼──────┐     ┌─────────┐
│    IPFS     │◄────┤ AI Agent│
│ (Encrypted) │     │ Verify  │
└─────────────┘     └─────────┘

Challenges we ran into

We ran into a lot of challenges this where the few significant challenges we faced:

Custom Wallet Connector for Talisman Wagmi doesn't have built-in Talisman support, so we had to create a custom connector:
```
const getTalismanProvider = () => {
if (typeof window === "undefined") return undefined;
return (window as WindowWithTalisman).talisman?.ethereum;
};
```
This required careful TypeScript typing and handling SSR edge cases.
Contract Interaction Edge Cases
Gas estimation failures when users had insufficient WND
Race conditions when listing/buying simultaneously
Stale data after transactions completed
Deploying to Westend Asset Hub testnet using Remix polkadot IDE

Accomplishments that we're proud of

What we learned

This project was a crash course in modern blockchain development:

Technical Skills

Smart Contract Security: Learned about reentrancy guards, access control, and safe math
EVM Compatibility: Polkadot's Asset Hub runs a full EVM, making Solidity deployment seamless
React 19 Patterns: Server Components, async components, and streaming
Web3 UX: How to make blockchain interactions feel native and intuitive
TypeScript Mastery: Strict typing for contracts, proper error handling, generic hooks

Blockchain Concepts

Gas Optimization: Every operation costs money, we optimized storage layout and function calls
Event-Driven Architecture: Using contract events to update UI state
Tokenomics: Designing pricing mechanisms and marketplace fees (even if we set them to 0%)
Wallet Integration: Supporting multiple providers (MetaMask, Talisman)

Soft Skills

Problem Decomposition: Breaking down "build a data marketplace" into manageable chunks
Debugging Persistence: Spent hours tracking down hydration bugs and build failures
Documentation Reading: Learned to navigate Wagmi, Viem, Polkadot, and OpenZeppelin docs
User Empathy: Realized blockchain UX needs to hide complexity, not flaunt it

What's next for Devra

Having established a strong foundation, our next steps will focus on deeper integration and optimization within the Polkadot ecosystem.

Integrate Native Precompiles: Leveraging Polkadot's utility pallet for features like batchAll
Optimize Marketplace: Making transactions even more secure and efficient for users and developers.
Expand Ecosystem: Further empowering developers and data providers within the Polkadot network.

Built with ❤️ by the Devra team Making data trading fair, transparent, and decentralized, one NFT at a time.