What is HMAC Authentication?
HMAC is a Hash-based Message Authentication Code. From the full form of HMAC, we need to understand two things one is Message Authentication Code and the other one is Hash-Based. So HMAC is a mechanism that is used for creating a Message Authentication Code by using a Hash Function. HMAC is a mechanism for calculating a message authentication code involving a hash function in combination with a secret key. The most important thing that we need to keep in mind is that while generating the Message Authentication Code using the Hash Function we need to use a Shared Secret Key. Moreover that Shared Secret Key must be shared between the Client and the Server involved in sending and receiving the data. It is a type of message authentication code (MAC) that is acquired by executing a cryptographic hash function on the data (that is) to be authenticated and a secret shared key.
Why HMAC is used?
This can be used to verify the integrity and authenticity of a message. It is a cryptographic technique that combines public keys, private keys, and a hash into a mix hackers can’t unpack. Using these values, the client will generate a unique HMAC (a hashed code) representing its request to the server. HMACs provides client and server with a shared private key that is known only to them. The client makes a unique hash (HMAC) for every request. When the client requests the server, it hashes the requested data with a private key and sends it as a part of the request. Both the message and key are hashed in separate steps making it secure. When the server receives the request, it makes its own HMAC.
The formula for HMAC:
HMAC = hashFunc(secret key + message)
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