How to Use the HMAC-SHA512 Generator

Enter your message in the message field.

Enter your secret key.

The HMAC-SHA512 tag is computed instantly and displayed as a 128-character hexadecimal string.

Copy the output for use in your security pipeline, JWT workflow, or verification system.

What Is HMAC-SHA512?

HMAC-SHA512 is the HMAC construction applied using SHA-512 as the underlying hash function. It produces a 512-bit (128-character hex) authentication tag — the largest output in the SHA-2 HMAC family. SHA-512 operates on 64-bit words and processes 1024-bit blocks, making HMAC-SHA512 particularly efficient on 64-bit hardware for large messages. It is used in JWT tokens signed with HS512, high-security API authentication schemes, key derivation functions, and cryptographic protocols that require maximum MAC output length. Like all SHA-2 variants, SHA-512 has no known practical vulnerabilities.

When to Use This Tool

JWT HS512 debugging — JWT tokens signed with HS512 use HMAC-SHA512. Reproduce the signature manually to debug token signing or verification failures.

High-security API authentication — Use HMAC-SHA512 when maximum authentication tag length is required by a security policy or protocol specification.

Key derivation inputs — HMAC-SHA512 is a component in several key derivation functions (e.g., HKDF with SHA-512) used in cryptographic protocol implementations.

Comparing HMAC output sizes — Use alongside HMAC-SHA256 to compare authentication tag lengths and understand the security-size trade-off across SHA-2 HMAC variants.

Related Tools

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