What is HMAC256 Algorithm :
HMAC ( Expanded as keyed-hash message authentication code or hash-based message authentication code) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key.
HMAC can provide authentication using a shared secret instead of using digital signatures with asymmetric cryptography.
HMAC (Hash-based Message Authentication Code) is a mechanism for verifying the authenticity and integrity of a message using a cryptographic hash function. HMAC-256 is a specific variant of HMAC that uses the SHA-256 hash function.
The HMAC-256 algorithm takes as input a secret key and a message and produces a fixed-size output (256 bits) that serves as a digital signature for the message. The steps involved in generating an HMAC-256 code are as follows:
- If the key is longer than the block size of the hash function (i.e., 64 bytes for SHA-256), the key is hashed using the same hash function to produce a fixed-length key.
- The key is then XORed with a specific constant (0x5c5c5c… for the outer hash and 0x363636… for the inner hash) to produce two different keys.
- The message is hashed using the first key.
- The resulting hash value is then hashed again using the second key.
- The final hash value is the HMAC-256 code.
The resulting HMAC-256 code is a string of 64 hexadecimal characters. It can be used to verify the authenticity and integrity of a message by comparing it with the expected HMAC-256 code generated using the same secret key and message.
HMAC-256 is commonly used in a wide range of applications, including secure messaging, authentication, and data integrity checking.
HMAC256 Functionality :
HMAC256 (Hash-based Message Authentication Code using the SHA-256 hash function) provides a way to authenticate the integrity and authenticity of a message using a secret key and a cryptographic hash function.
The HMAC256 function takes two inputs:
- A secret key is a shared secret known only to the sender and receiver of the message. The key is used to create the HMAC code and verify its authenticity.
- A message, which is the data being protected by the HMAC code.
The HMAC256 function then performs the following steps:
- If the secret key is longer than the block size of the hash function, it is hashed using the same hash function to produce a fixed-length key.
- Two keys are derived from the secret key, one for the inner hash and one for the outer hash.
- The message is hashed using the inner key and the resulting hash value is then hashed again using the outer key.
- The final hash value is the HMAC256 code, which is a fixed-length string of characters.
The HMAC256 code can be sent along with the message to the receiver. The receiver can then use the same secret key and HMAC256 function to calculate the HMAC code for the received message. If the calculated HMAC code matches the received HMAC code, then the message has not been tampered with and the authenticity and integrity of the message can be verified.
HMAC256 is commonly used in a wide range of applications, including secure messaging, authentication, and data integrity checking.