HMAC

HMAC, or Hash-based Message Authentication Code, is a method used to verify that a message or data is authentic and hasn't been altered during transmission. It combines a secret key with the message and then runs this combination through a hash function—a mathematical process that creates a unique string of characters. If the message is tampered with, the resulting hash will change, alerting the receiver that the data may not be trustworthy. HMAC thus ensures both data integrity and authenticity, commonly used in secure communications and online security protocols.