The Message Authentication Code (MAC) is a widely used technique for performing message authentication. HMAC (short for "keyed-Hashing for Message Authentication"), a variation on the MAC algorithm, has emerged as an Internet standard for a variety of applications.
It involves hashing a message with a secret key. As with any MAC, it can be used with standard hash function, such as MD5 or SHA-1, which results in methods such as HMAC-MD5 or HMAC-SHA-1. As with any hashing function, the strength depends on the quality of the hashing function, and the resulting number of code bits.
Message Digest (hash) engine allows direct processing of arbitrary length messages using a variety of hashing algorithms.
Returns a string containing the calculated message digest as lowercase hexits.
HMAC authentication is a shared-secret cryptography method where signatures are generated on the client side and validated by the server in order to authenticate the request.
This helps to authenticate the message. The secret key is known both by the sender and the receiver of the message.
Essentially HMAC is like a mix between one-way hashing and key based encryption. HMAC security relies on the key size used, and strength of the hash function used for the calculation. The secure hash algorithm is used to provide integrity and you will need a secure cryptographic hash with very specific properties. Cryptography is all about preventing attackers from doing malicious things.
HMAC is used in TLS to generate the key material that is used to create keys for cryptographic use. A pseudo random number generator provides the need function for creating public-private key pair. TLS uses Message Authentication Codes (MACs) to perform message integrity checks and determine whether a message has been altered over the nerwork. TLS uses HMAC, allowing it to work with a wide variety of hash functions; including MD5 and SHA.