HMAC-SHA512 Generator

Generate an HMAC-SHA512 code for high-entropy signatures on large payloads and long-lived tokens.

Secret:

Input

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Output

Output will appear here...

What is HMAC-SHA512 Generator

Last reviewed: April 18, 2026

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-SHA512 Generator returns the RFC 2104 HMAC of a message computed with the SHA-512 hash function, as a 128-character hexadecimal string.

HMAC-SHA512 is common in high-assurance signing, long-lived token validation, JWT HS512, and bandwidth-insensitive API authentication where a 512-bit MAC is preferred.

Why use it

Sign and verify JWT HS512 tokens quickly in the browser.
Produce HMACs for long-lived tokens and session identifiers.
Match enterprise spec vectors that require 512-bit MACs.
Double-check library output when implementing HMAC-SHA512 in a backend service.
Generate deterministic signing material for audit logs.

Features

128-character HMAC-SHA512 hex output
Matches OpenSSL, Node.js, Go, Python libraries
JWT HS512 compatible
Client-side signing — nothing is uploaded
Instant recompute on edit

How to use HMAC-SHA512 Generator

Paste the message. Drop the canonical payload you want to sign into the input panel.
Enter the secret. Paste the shared secret into the Secret field.
Copy the signature. The 128-character hex HMAC-SHA512 signature updates in the output panel for copying.

Example (before/after)

Message + key

message: audit-log-entry
key: sha512-audit-key

HMAC-SHA512 hex digest

77e2ff11d2c10d5aa2df4d0e8f3ca20f4c9ad5d6f79ab3db38b2d6b48e34fb3f1aef726eb1e3bd95eb9b88c0ecb0c62a3f10b2f8ef7f8a3cf86d3f2d3d2dbc6a

Common errors

Treating HMAC-SHA512 as automatically better

HMAC-SHA256 is already strong. The 512-bit output only matters when the spec requires it or when you want a matched ECDSA P-521 pairing.

Fix: Use HMAC-SHA256 unless a longer output is required.

Truncating the digest

The 128-character digest wraps easily and is often cropped by terminals.

Fix: Copy with the button to preserve the full digest.

Key format mismatch

Passing a base64 or hex key as raw UTF-8 produces a different signature than your peer expects.

Fix: Decode the key to raw bytes before signing, or ensure both sides use the same encoding.

FAQ

What output length?

512 bits (128 hex characters).

Is it compatible with JWT HS512?

Yes. HS512 uses HMAC-SHA512 with base64url encoding of the signature.

Does this tool match Node.js crypto?

Yes. `crypto.createHmac('sha512', key).update(msg).digest('hex')` returns the same output.

Is HMAC-SHA512 FIPS approved?

Yes. It is a standard HMAC variant under FIPS 198-1 with SHA-512.

Does the tool run offline?

It runs client-side, so once the page loads you do not need a network connection for signing.

Can I import a binary key?

Convert binary keys to hex or base64 and decode accordingly; the Secret field accepts UTF-8.

Related tools

Compare HMAC-SHA512 with other HMAC variants or pair it with related crypto tools. You can also browse the full Cryptography & Hashing category for more options.

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