ECDSA Tool

This tool enables signing and verification using ECDSA across common curves such as secp256k1 and NIST P-256. It is designed for developers, security engineers, and testers who need to validate digital signatures in client-side or offline contexts. By providing inputs for a message, a chosen curve, a hash function, and the appropriate key material, users can generate signatures or confirm existing ones without server involvement.
Conceptually, the tool implements the standard ECDSA equations. For signing, it hashes the message to z, selects a nonce k (deterministic when RFC6979 is enabled), computes r as the x-coordinate of kG modulo n, and computes s as k inverse times (z + rd) modulo n. For verification, it uses the public key Q and the signature (r,s) to recompute a point on the curve and checks that r matches the derived x-coordinate modulo n. Outputs include r, s, an optional DER-encoded signature, and a boolean verification result.
Who benefits: developers integrating blockchain transactions, API request signing, or secure message exchange; testers who compare against reference vectors; security researchers exploring curve behaviors. Unique value includes multi-curve support in a single browser tool, deterministic nonce options, and canonicalized signatures to reduce malleability. It can emit derived values to aid debugging and demonstration.
Core features: input validation, multiple curves, hash options, hex formatting, optional deterministic signing, and DER output; exportable components to feed into other tooling; clear error codes for invalid inputs; and a no-dependency, client-side implementation suitable for quick experiments.