ECDSA Sign Message

Sign a message with ECDSA

ECDSA creates a digital signature from a message, elliptic-curve private key, and hash algorithm. The signature can be checked with the corresponding public key to detect changes and authenticate the signing key holder.

Select the curve, message encoding, digest, private-key representation, and signature output encoding required by the receiving system. Signing does not encrypt the message or make it confidential.

How to create an ECDSA signature

1. Enter the exact message and select how it becomes bytes.
2. Choose the curve and hash algorithm expected by the verifier.
3. Paste the private key as PEM, Hex, or Base64 and enter its PEM passphrase when applicable.
4. Sign and retain the algorithm, curve, signature encoding, and matching public key.

Any difference in whitespace, line endings, character encoding, or serialization changes the signed bytes.

ECDSA security and compatibility

NIST FIPS 186-5 specifies ECDSA. Curve acceptance and digest requirements still depend on the application protocol. The default secp256k1 curve is distinct from NIST P-256 even though both use 256-bit parameters.

ECDSA requires a unique, unpredictable per-signature nonce. A broken implementation that repeats or biases this nonce can expose the private key; use reviewed libraries and protected key storage for production signing.

ECDSA signing FAQ

Does signing hide the message?

No. Encrypt separately when confidentiality is required.

Can the public key create a signature?

No. Only the private key signs; the public key verifies.

How do I verify the result?

Use ECDSA Verify Signature with the exact message bytes, curve, hash, public key, and signature encoding.