Show members-only content to wallets that hold a pass
Beginner8h1–2
WagmiViemNext.js
16/20Document Hash Notary
Prove a document existed at a time without revealing its content.
Beginner8h1 person17/20 fit
Build Document Hash Notary for freelancers, researchers and lawyers in ~8h with 1 person. Stack: Viem + Web Crypto + Next.js.
Why it wins: Simple, privacy-preserving and understandable.
Build flow
01 · Problem
Proving you had a file at a certain date is hard.
02 · Solution
Hash the file locally, record the hash onchain or as an attestation and let anyone verify by re-hashing the file.
03 · Build
- 1Hash in browser
- 2Write to chain
- 3Build verify page
- 4Handle batches
04 · Demo
Notarise a file and verify it; change one byte and it fails.
MVP checklist
- Local hashing
- Timestamp record
- Verify page
- Batch mode
Tech stack
| Tech | Role | |
|---|---|---|
| Viem | Ethereum client | Chain |
| Web Crypto | Tooling | Tool |
| Next.js | Frontend + API routes | Web |
Reference repos
Open-source projects you can build on. Links checked 2026-10-31.
Related ideas
More Web3Know the cheapest time to send a non-urgent transaction
Beginner8h1ViemEChartsNext.js16/20Run transparent elections where each member votes once
Beginner10h1–2SolidityScaffold-ETHNext.js17/20