We’ve deployed a small experiment on Kusama’s EVM: an expense splitting app where all data is encrypted before it touches the chain.
Why build this?
Most expense splitting apps require accounts, servers, and trust. Your spending data sits on someone else’s infrastructure. We wanted something different: a tool where the blockchain is just encrypted storage, and only group members hold the keys.
No accounts. No servers. No data harvesting. Just your wallet and your friends.
How it works
When you create a group, a symmetric key is generated locally. That key is encrypted to each member’s public key (ECIES) and stored on-chain. Expenses are encrypted with ChaCha20-Poly1305 before submission. The contract only sees ciphertext.
Even if someone reads the chain directly, they see nothing but encrypted blobs and wallet addresses.
Why Kusama?
Kusama felt right for this. It’s a network for experiments, for things that might break, for people who prefer sovereignty over convenience. The EVM compatibility made deployment straightforward, and the community values align with what we’re trying to build.
What it is (and isn’t)
This is a simple tool for splitting bills with friends. It’s not trying to be a protocol or a platform. It works offline (cached locally), syncs when you’re online, and does one thing reasonably well.
It’s also fully open source: hantoniu/splitex: Privacy-first expense splitting with end-to-end encryption on EVM blockchains - Codeberg.org
Try it
Android APK available on Codeberg. If you’d like to stay up to date, you can add the repo to Obtainium for automatic updates.
Create a wallet, start a group, add expenses. If something breaks, we’d love to hear about it.
Contract: Kusama Asset Hub address details for 0xD57B48C472061A1e046e6623d2B46b33E0DA557C | Blockscout