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HMAC-SHA3 Generator

Generate an HMAC-SHA3 keyed-hash authentication code using the Keccak family for modern cryptographic workflows.

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Input
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Output

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What is HMAC-SHA3 Generator

Last reviewed:

HMAC (Hash-based Message Authentication Code) combines a cryptographic hash with a secret key to verify both the integrity and authenticity of a message.

HMAC-SHA3 Generator produces an HMAC using the FIPS 202 SHA-3 hash function and a shared secret key, returning the keyed digest in hexadecimal.

It is useful when you need algorithm diversity from SHA-2 or when a protocol specifies HMAC-SHA3 explicitly — for example, some post-quantum migration plans pair SHA-3 constructions alongside SHA-2 HMACs.

Why use it

  • Add SHA-3 based keyed authentication to workflows already using SHA-2.
  • Match HMAC-SHA3 reference vectors during library testing.
  • Avoid relying solely on SHA-2 for MACs in high-assurance systems.
  • Produce keyed digests that are structurally independent of SHA-256.
  • Generate interoperability vectors when migrating to SHA-3.

Features

  • HMAC-SHA3 hex output
  • FIPS 202 SHA-3 base
  • Runs entirely in the browser
  • Algorithm-diverse signing alongside SHA-2
  • Instant recompute on edit

How to use HMAC-SHA3 Generator

  1. Paste the message. Drop your canonical string into the input panel.
  2. Enter the secret. Paste the shared secret in the Secret field.
  3. Copy the signature. The HMAC-SHA3 hex digest updates as you type — copy it when ready.

Example (before/after)

Message + key

message: sha3-migration-vector
key: sha3-rollover-key

HMAC-SHA3 hex digest

b7e4a2ad76c8f6b1920c1c0f7b4ffa5f6ddf6aeccf94e02d4a3cd8bc25c1f1ad

Common errors

Confusing SHA-3 with Keccak

Pre-FIPS Keccak libraries use different padding than FIPS 202 SHA-3.

Fix: Match the variant your peer requires, specifically checking for the FIPS 202 padding byte.

Encoding mismatch in key

Passing a hex key as UTF-8 changes the effective bytes and therefore the HMAC.

Fix: Decode the key to bytes first, or agree on an encoding with your peer.

Expecting pre-FIPS Keccak output

This tool uses FIPS 202 SHA-3, not legacy Keccak.

Fix: Use a dedicated Keccak tool when targeting pre-standard implementations.

FAQ

What output length does HMAC-SHA3 produce?

By default it uses SHA3-256, so 256 bits (64 hex characters).

Can I pick the SHA-3 variant?

This tool focuses on SHA3-256. Use the dedicated tools for SHA3-224/384/512 HMAC variants when needed.

Is HMAC-SHA3 FIPS approved?

Yes, under FIPS 198-1 used with SHA-3 (FIPS 202).

How does it compare with HMAC-SHA256?

Both provide strong authentication. HMAC-SHA3 offers structural diversity from SHA-2.

Does my data leave the browser?

No. HMAC-SHA3 is computed on your device.

Why would I prefer SHA-3 here?

For algorithm diversity, regulatory requirements, or when implementing post-quantum migration plans.

Related tools

Combine HMAC-SHA3 with plain SHA-3 hashes and matched HMAC-SHA2 variants. You can also browse the full Cryptography & Hashing category for more options.

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