WhyTx

Your wallet remembers what. WhyTx remembers why.

WhyTx is a private memory and proof layer for crypto transactions. It lets a wallet owner attach encrypted context to a confirmed Monad transaction, preserve version history, selectively reveal fields, and prove that the revealed context matches a timestamped onchain commitment.

Built from scratch for the Spark hackathon, July 13–19, 2026.

Open the live app · Watch the onchain demo

The working loop

1. Connect a browser or mobile EVM wallet through Reown AppKit and sign a gas-free unlock message once per tab session.
2. Choose Monad Mainnet or Monad Testnet and import a confirmed transaction involving that wallet.
3. Add a purpose, category, counterparty label, status, follow-up date, and private details.
4. Encrypt the readable record locally with AES-GCM.
5. Secure a salted Merkle root on the selected Monad network; no readable note goes onchain.
6. Create a verification link containing only selected fields and their Merkle proofs.
7. Independently verify both the field proofs and the onchain anchor.
8. Edit the record as a new linked version; earlier anchors remain intact.

What it proves—and what it does not

WhyTx proves that a wallet created a particular cryptographic record at an onchain time, that the record was linked to a transaction, and that revealed values match that record. It does not prove a personal statement is true, agreed by the counterparty, or legally enforceable.

Privacy model

• A deterministic wallet signature derives a browser-local AES-256-GCM key.
• The derived key is cached in sessionStorage so a refresh does not require another signature; disconnecting or closing the tab clears the session.
• Full records and per-field random salts are stored only as ciphertext in localStorage.
• Each record field becomes a salted Merkle leaf. The contract receives only the root, original transaction hash, and previous-version ID.
• Reveal data is encoded in the URL fragment (#...), which browsers do not send to the hosting server.
• A verifier can check disclosed leaves without learning hidden values.

This hackathon implementation is local-first: clearing browser storage removes the encrypted records. A production release should add encrypted backup and a reviewed recovery design.

Stack

• React 19, TypeScript, Vite
• Reown AppKit with its Ethers v6 adapter for non-custodial wallet connections
• viem for Monad RPC and contract interaction
• Web Crypto API for AES-GCM
• Solidity WhyTxRegistry contract
• Vitest for cryptographic proof tests

Run locally

Requirements: Node.js 22+ and a Reown-compatible EVM wallet.

npm install
cp .env.example .env
npm run dev

Run every check:

npm run check

That command runs linting, unit tests, Solidity compilation, TypeScript, and the production build.

Contract

The contract is intentionally small and append-only. Compile it with:

npm run contract:compile

The build artifact is written to artifacts/WhyTxRegistry.json.

Deploy to mainnet with a funded key supplied only through the environment:

DEPLOYER_PRIVATE_KEY=0x... npm run contract:deploy:mainnet
npm run contract:verify-mainnet

Monad Mainnet deployment

• Contract: 0xc5e6f9952e5dd685f073922ad1221cdaad4f46f9
• Deployment transaction: 0x2ea390ac6909a1798e10d4cacab3adace368f60f90bf2b303d125b27cdb1e143
• Integration test: 0xf003a809e3778f3ac5a6fe521fad39c3bf161743da133d1f8b91f18dc1689912 (event and persisted fields verified)
• Deployment metadata: deployments/monad-mainnet.json

Monad Testnet deployment

• Contract: 0x3ccacaa6fa6ca64e1f8f8f8f448f0a5a97581129
• Deployment transaction: 0x0e1994fdce64e130d3e00de263b675c4cdf711d25c0e8a82f1b72650b51e3bf9
• Integration test: 0xbe274c628f38925228e4437c31d5b8697f00aad4201966c4ac94f00ae0b271ed (event and persisted fields verified)
• Source verification: perfect match on MonadVision
• Deployment metadata: deployments/monad-testnet.json

Networks

• Monad Mainnet — chain ID 143, RPC https://rpc.monad.xyz, explorer https://monadscan.com
• Monad Testnet — chain ID 10143, RPC https://testnet-rpc.monad.xyz, explorer https://testnet.monadexplorer.com

Connected users can switch between both networks from the dashboard. Transaction imports, contract writes, explorer links, and verification links remain bound to the selected chain.

Project structure

contracts/             onchain commitment registry
scripts/               reproducible Solidity compiler
src/lib/chain.ts       live Monad reads and wallet client
src/lib/appkit.ts      Reown wallet connection and Monad network setup
src/lib/merkle.ts      field commitments and selective proofs
src/lib/vault.ts       browser encryption
src/lib/reveal.ts      privacy-preserving verification links
src/App.tsx            product UI and complete user flow

License

MIT