TASK

Implement ECDSA signatures

ECDSA (Elliptic Curve Digital Signature Algorithm) provides digital signatures with smaller keys than RSA. Learn signing and verification.

1

ECDSA: to sign message m with private key d, compute e = hash(m), pick random k, compute (x, y) = k*G, r = x mod n, s = k^(-1)(e + r*d) mod n. Signature is (r, s). To verify with public key Q = d*G: compute w = s^(-1) mod n, u1 = e*w, u2 = r*w, (x, y) = u1*G + u2*Q, verify x mod n = r. The random k must never repeat or leak — this broke PlayStation 3 and some Bitcoin wallets.
2

HMAC Generator →
Generate a deterministic HMAC for the message. ECDSA requires a hash of the message — use SHA-256. For deterministic ECDSA (RFC 6979), derive k from the private key and message hash using HMAC, eliminating the need for random k and preventing nonce reuse vulnerabilities.
3

Hash Calculator →
Hash the message with SHA-256 before signing. The hash reduces the message to a fixed-size digest that fits in the curve's field. Use SHA-256 for P-256, SHA-384 for P-384. Never use MD5 or SHA-1 — they are broken and allow signature forgery.

Frequently asked questions

What happens if the ECDSA nonce k is reused?: Catastrophic key compromise. If two messages are signed with the same k, an attacker can compute the private key d from the two signatures. This broke Sony PlayStation 3 (static k) and some early Bitcoin implementations. Use deterministic ECDSA (RFC 6979) to eliminate this risk.
ECDSA vs EdDSA?: ECDSA requires a random nonce per signature (or deterministic derivation). EdDSA (Ed25519) is deterministic by design, uses Edwards curves (faster, simpler, no special cases), and is strongly unforgeable. Use Ed25519 (EdDSA) for new systems — it is simpler, faster, and avoids the nonce pitfall.

Workflows that solve this

Hash content and encode as Base64

Compute a hash of the input and encode the hash digest as Base64 for compact transport.

Hash text and verify integrity

Compute a hash of the input text and compare it against an expected hash to verify integrity.

Hash text and verify with CRC32 checksum

Compute both a cryptographic SHA-256 hash and a CRC32 checksum for data integrity verification.

HMAC Sign then Base64 Encode

Generate HMAC signature then Base64-encode for API auth headers.

HMAC sign and verify

Generate an HMAC signature for a message and verify it against an expected signature.

HMAC-sign an API request string

Generate an HMAC-SHA256 signature for a request payload to authenticate API calls.

MD5 Hash then Base58 Encode

Compute MD5 hash then encode as Base58 for compact representation.

Multi-hash speed comparison

Hash the input and benchmark multiple hash algorithms to compare their speed and output.

Generate Password and Hash

Generate a random password then hash it for secure storage.

SHA3-256 Hash with CRC32 Checksum

Compute SHA3-256 hash then CRC32 checksum for dual integrity verification.

SHA-512 Hash then Hex Encode

Compute SHA-512 hash then encode as hex for readability.

Reverse Text and Hash

Reverse text then compute SHA-256 hash of the reversed result.

Scramble Text and Hash

Scramble text then hash the scrambled result.

Learn more

Want to understand why?

Choosing a hash algorithm: digests, password hashing, and MACs are three different jobs

A field guide to SHA-2, SHA-3, BLAKE2, MD5, bcrypt/Argon2, and HMAC — which one fits integrity checks, password storage, and message authentication, and why they are not interchangeable.

How to Chain Encoding and Hashing Workflows

Real data-processing tasks rarely use a single tool. This tutorial shows how to compose encoding and hashing tools into multi-step pipelines: a base64-to-hash-to-hex verification chain, parallel multi-algorithm integrity checking, and an automatic encoding-format conversion chain. Each pattern maps to an existing workflow recipe (base64-encode-decode-verify, hmac-sign-verify) and explains when to use inline tool chaining versus a saved recipe.

BLAKE3 Keyed Mode

The BLAKE3 keyed mode is BLAKE3's MAC mode: a 32-byte key is injected into the initial state to produce a keyed message authentication code.

A hash chain is a sequence obtained by repeatedly hashing the same value, h^0=x, h^i=H(h^{i-1}), used for one-time passwords and lightweight authentication.

Related tools

Generate HMAC (Keyed-Hash Message Authentication Code) with SHA-1/256/512. Free, private, and 100% client-side.

Hash Calculator

Compute MD5, SHA-1, SHA-256, or SHA-512 hashes with hex or Base64 output. Free, private, and 100% client-side.

Modular Exponentiation

Modular Exponentiation — pure client-side tool. Privacy-first, no server round-trip.