HMAC
HMAC (Hash-Based Message Authentication Code) is a cryptographic technique that combines a secret key with a hash function to verify both the integrity and authenticity of a message. It produces a fixed-size output (the MAC) that can be sent alongside the message, allowing the receiver to recompute it with the same key to detect tampering or forgery. It is widely used in secure communication protocols, APIs, and data storage to ensure data has not been altered by unauthorized parties.
Developers should learn HMAC when building systems that require secure message verification, such as API authentication (e.g., in webhooks or REST APIs), digital signatures, or data integrity checks in distributed systems. It is particularly useful in scenarios where symmetric keys are shared between parties, as it provides a lightweight and efficient way to prevent replay attacks and ensure message trustworthiness without the overhead of full encryption.