Interactive demo · try it yourself
Signing: prove it's you, without showing the key
This is the magic trick at the heart of Bitcoin. You sign a payment with your private key — and anyone can confirm the signature could only have come from that key, yet no one can work backwards from it to the key itself. Watch it happen, then try to cheat it.
The key below is randomly generated in your browser and thrown away when you leave. Never enter your real seed or keys anywhere. These are real signatures, over a fake payment.
Generate a throwaway key, sign a payment, then try tampering with it.
Runs entirely in your browser · nothing is sent, saved, or logged.
The payment you're approving
The private key never left — only the signature did, and the signature is glued to that exact payment. Change one character and it stops verifying, so a thief can't reuse it or reroute your coins. This is why a hardware wallet can sign on a malware-riddled computer and still be safe: it sends out proof, not the key.
✓ Last verified: July 30, 2026