HMAC
This module implements the HMAC algorithm, as described by RFC 2104 (https://datatracker.ietf.org/doc/html/rfc2104.html). HMAC (which stands for hash-based message authentication code or keyed-hash message authentication code, depending on who you ask) is a widely used mechanism for authenticating messages and verifying that they have not been tampered with.
The algorithm combines a message with a secret key and generates a hash of the combination. This hash is referred to as a message authentication code (MAC) or signature. The signature is stored or transmitted along with the message. You can verify that the message has not been tampered with by re-computing the signature using the same secret key and comparing it to the previously computed signature. The secret key must be carefully protected; otherwise, an attacker with access to the key would be able to modify the message and replace the signature, thereby defeating the authentication mechanism.
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