The message that originated from an authorized user is defined as User Authentication and is provided by Message Authentication codes (MAC). The provision of assurance that the message is not been modified is defined as Message Authentication and is provided by Hash functions. Authenticated code is generated when MAC uses Hash function it is called Hash based MAC (HMAC). In this paper an algorithm is proposed for HMAC which uses SHA-2 as cryptographic hash function. The algorithm is implemented using GUI based controls in MATLAB toolbox which enables the algorithm to be friendly with the user. Theoretical analysis and experimentation show that this hash function is with high plaintext sensitivity and low collision resistance, and secure against birthday attacks or meet-in-the-middle attacks. These properties make it a suitable choice for data signature or authentication.