ECDSA Sign & Verify Tool
Generate an ECDSA (P-256) key pair, sign a message and verify the signature in your browser — the digital-signature scheme behind TLS, JWTs and crypto wallets.
About ECDSA Sign & Verify Tool
ECDSA Sign & Verify Tool generates a P-256 key pair, signs a message with the private key and verifies it with the public key — all in your browser. It's the hands-on way to understand the digital signatures behind TLS, JWTs (ES256) and crypto wallets.
How to use ECDSA Sign & Verify Tool
- 1Paste or type your input into the box above — a sample is pre-filled so you can try it instantly.
- 2Set any options on offer (mode, key, format) to match what you need.
- 3The result appears the moment you type — no button to press, no waiting.
- 4Click Copy to grab the output — ECDSA Sign & Verify Tool keeps everything on your device.
Why use ECDSA Sign & Verify Tool?
- ✓Learning how digital signatures prove authenticity and integrity
- ✓Demonstrating tamper-detection: edit a signed message and watch verification fail
- ✓Experimenting with the ES256 algorithm used in JWTs and WebAuthn
- ✓100% free with no sign-up, no watermark and no usage limits
- ✓Runs entirely in your browser — your text and keys are never uploaded, stored or logged
- ✓Works offline once loaded, with instant results and one-click copy
Frequently asked questions
What is the difference between signing and encryption?+
Encryption hides a message; signing proves who sent it and that it wasn't changed. With ECDSA you sign with your private key and anyone can verify with your public key — the opposite key direction from encryption, and it does not conceal the message.
Is ECDSA P-256 secure?+
Yes — P-256 with SHA-256 (ES256) offers roughly 128-bit security and is widely used in TLS, JWTs and passkeys. Its main historical pitfall is reusing or leaking the per-signature random value, which Ed25519 avoids by design.
Is it free to use?+
Yes — completely free with no sign-up, no account and no usage limits. There is no paywall, so you can encode, decode and convert as much as you like.
Is my data private and secure?+
Yes. This tool runs entirely in your browser using client-side JavaScript — your input is never uploaded to a server, stored or logged. Once the page has loaded you can use it offline, which makes it safe for tokens, keys and confidential data.
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