What is ECDSA?
ECDSA signing creates a digital signature using your elliptic-curve private key, proving a message came from you and was not altered. Anyone with your public key can verify it. ECDSA signatures are small and fast and are used widely in TLS, SSH and blockchains. Signing runs entirely in your browser, so your private key never leaves your device.
Authenticity: a signature proves who sent a message and that it is unchanged. Verify it with the ECDSA Verify tool. Runs locally.
How ECDSA works
ECDSA signing produces a pair of numbers (r, s):
- The message is hashed (for example with SHA-256).
- A secure random nonce k is chosen for this signature.
- Curve math combines the hash, the private key and k to produce the signature (r, s).
How to use
- Paste your message and your ECDSA private key.
- Choose the algorithm options.
- The signature is produced in your browser.
Options explained
- Curve — Must match the key (for example P-256 or secp256k1).
- Hash algorithm — The digest used before signing (SHA-256 and others).
- Private key — Paste your EC private key (PEM).
Common uses
- Signing blockchain transactions (Bitcoin, Ethereum).
- JWT signing with ES256.
- Code and document signing.
Frequently asked questions
Why must the nonce be random?
Reusing or leaking the nonce k can expose the private key, so it must be unique and unpredictable per signature.
What does the signature contain?
Two values, r and s, derived from the hash, private key and nonce.
How do I verify it?
Use the ECDSA Verify tool with the public key.