Compute HMAC-SHA512 message authentication codes

Create an HMAC-SHA-512 authentication tag for a message and shared secret.

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ToolHMAC-SHA512
Input
Output
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How it works

HMAC hashes an inner pad concatenated with the message, then hashes an outer pad concatenated with that inner digest. SHA-512 supplies the compression function and a 128-byte block size; keys longer than the block are hashed first.

  • HMAC separates key mixing from message hashing and avoids naïve length-extension constructions.

Worked example

Compute HMAC-SHA512 message authentication codes
Generate an HMAC-SHA512 authentication code for a message
Input
											Input: Hello, World!
Key: MySecretKey123!
Output
												3eae1073dc45c5a21427c85daf48fd6e6d56ab14e15d72209119e5651566727b11cd30d68d3adb9c21f246c4e518065481e89889c4426d77c741e9ce890e601b

When to use this

API request signing, webhook verification, and shared-secret protocols create HMAC tags.

Edge cases

  • Changing one key byte changes the tag.
  • Comparing tags with an early-exit string check can leak timing.
  • HMAC authentication does not encrypt the message.

References