Lumen Bank

A sandbox bank that only moves money Countersign signed. When the Policy Engine says PAY, the Payer signs that exact transfer: who, how much, which invoice, once. Anything without a valid countersignature is refused at the door.

Operating account

Payees on file

routing and last 4 only

Simulate a hijacked agent

Suppose an attacker controls an AI agent with network access and skips Countersign to talk to the bank directly. These are four real requests to the bank's public transfer endpoint, sent from this page.

1
No signature
A perfectly formed $48,000 transfer, sent straight to the bank.
Not sent
2
Its own key
The same transfer, signed with a key this page just made.
Not sent
3
Edit a real one
A real countersigned transfer with the amount changed to $48,000.
Not sent
4
Replay a real one
A real countersigned transfer, sent again byte for byte.
Not sent

POST insightful-otter-553.convex.site/bank/transfers

Transfer ledger

Live

Result	Transfer	Bank's answer	Door	Time

Sandbox bank, fictional company, no real money. In this demo the bank and the signer run in one backend, and the bank only ever reads the public key. In production the bank holds only the public key and the signer runs in its own isolated service.