How HMAC works, step-by-step explanation with examples

Oleksandr Volkov·Follow9 min read·Dec 17, 2023--HMAC (Hash Message Authentication Code) is an approach for creating digital signatures using different hash algorithms like MD5, SHA1, SHA256, SHA512, etc…Why do we need HMAC?Short answer — for digital signatures (DA) which give us data Integrity and authentication. This is a unified approach for applying a digital signature with a private key. Let’s take a quick look at how hashing-based DA works (This part is optional and you can skip it).Let’s consider a scenario where Alice wants to securely send a message to Bob, ensuring that the message remains unchanged during transmission. Simultaneously, Bob needs to verify that the message indeed originated from Alice. To achieve this, Alice decides to enhance security by incorporating a secret key into the hashed message. For a more in-depth understanding of this process, refer to the details on how Digital Authentication (DA) works.In practice, Alice combines the secret key with the hashed me...