👻 SealBid: The Ghost Auction — Where Every Bid Is Hidden Until It's Time
This is my submission for the Hacktoberfest Open-Source AI Challenge Week 4: Ghost in the Machine.
What if an auction had a ghost?
A participant who could influence the outcome, but whose intentions remained completely invisible until the right moment?
That's the idea behind SealBid, a sealed-bid auction platform built on Stellar Soroban smart contracts.
What I Built
SealBid is a commit-reveal sealed-bid auction platform designed to make auctions more private, transparent, and trustworthy.
Traditional online auctions expose bids while the auction is happening. This can encourage last-second bidding, copying competitors, and strategic price manipulation.
SealBid takes a different approach.
Instead of immediately submitting a visible bid, participants first submit a cryptographic commitment: a SHA-256 hash generated from their bid amount and a secret.
The actual bid remains hidden during the commit phase.
When the reveal phase begins, bidders reveal their amount and secret. The smart contract independently verifies that the revealed information matches the original commitment.
Once the auction ends, the smart contract settles the auction:
- The highest valid revealed bidder wins.
- Losing bidders automatically receive their escrowed funds back.
- The winner's escrowed funds are released to the seller.
- Settlement is protected against repeated execution.
The interesting part is that the system doesn't need to trust the auction operator to handle the money. The Soroban smart contract is responsible for escrow, refunds, and payouts.
The ghost is the hidden bid: present in the system, committed cryptographically, but invisible until reveal time.
Demo
🚀 Live application: https://bid-aution.vercel.app/
🎥 Video demonstration: Watch the project demo
You can explore the auction experience, bidding interface, and application flow.
Code
💻 GitHub Repository: https://github.com/Tusharkhadde/Bid-aution
The repository contains the frontend, backend, and Soroban smart contract implementation.
How I Built It
I built SealBid using a combination of web technologies, blockchain infrastructure, and cryptographic verification.
Frontend
- Next.js
- React
- TypeScript
- Stellar Freighter wallet integration
Backend
- Node.js
- WebSockets
- Prisma ORM
- PostgreSQL (Neon)
Blockchain
- Stellar
- Soroban smart contracts
- Rust
- SHA-256 cryptographic commitments
How the commit-reveal mechanism works
1. Commit phase
A bidder generates a secret and combines it with their intended bid amount.
The application generates a SHA-256 commitment:
SHA256(amount || secret)
Only the resulting hash is submitted to the smart contract. The actual bid amount remains hidden.
2. Reveal phase
After the commit deadline, bidders reveal their original amount and secret.
The contract recomputes the hash and compares it against the stored commitment. If they don't match, the transaction is rejected.
3. Settlement phase
After the reveal deadline, the smart contract determines the highest valid bid and handles the escrowed funds.
Losing bidders are refunded, while the winner's funds are transferred to the seller.
The role of AI and open-source technology
I used open-source development tools and frameworks to build and integrate the application.
The core auction mechanism is implemented through a Rust-based Soroban smart contract, rather than relying on a centralized backend to determine the financial outcome.
Transparency: The project uses publicly inspectable smart contract code and an open-source repository.
Note: The core commit-reveal mechanism is cryptographic, not an AI model. I am not claiming that an open-weight AI model powers the auction.
Why Does Open Innovation Matter?
Open innovation matters because financial infrastructure should not require blind trust.
With closed systems, users often have to trust the platform's internal implementation. They may not know exactly how bids are handled, how winners are selected, or how money is distributed.
Building with open-source infrastructure allows developers and users to inspect the implementation, understand the rules, and contribute improvements.
For SealBid, open innovation made it possible to build around:
- Open and inspectable smart contracts.
- Publicly available cryptographic verification logic.
- An open-source frontend and backend.
- Stellar's blockchain infrastructure.
- Reusable technologies that other developers can fork and extend.
The goal is not simply to build another auction website. It is to explore how decentralized infrastructure can make digital auctions more trustworthy.
My Agent Session
Not included in this submission.
The Spirit of It
The most interesting thing about this project is the moment when hidden bids become visible.
Imagine several people participating in the same auction.
Everyone has committed their bid. Nobody knows what anyone else has offered. No one can simply watch the highest bidder and adjust their price.
Then the reveal phase begins.
The hidden information finally becomes public, and the smart contract verifies what everyone committed to earlier.
That moment is what inspired the connection to Ghost in the Machine.
Something invisible was influencing the entire process. It was there all along, waiting to be revealed.
No visible bids. No guessing competitors' prices. Just cryptographic commitments and a transparent settlement.
Prize Categories
Project submission for the Hacktoberfest Open-Source AI Challenge Week 4: Ghost in the Machine.
Built with open-source technologies including Rust, Soroban, Stellar, Next.js, React, Node.js, and PostgreSQL.
Built by @Tusharkhadde.
Thanks for checking out SealBid! 👻
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