With the fast progression of digital data exchange in electronic way, information security is becoming more important in data storage and transmission. Cryptography has come up as a solution which plays a vital role in information security system against malicious attacks. The confidentiality, Integrity and Availability are the three main goals of Information Security. To protect Confidentiality and Integrity of the message, key mechanisms and Hash functions are used. This paper proposes a novel scheme, which computes Hybrid HMAC based on improved SHA-512 algorithm. The proposed system gives a constant output of 512 bits for any input length of data and generates HMAC using multiple available keys. Paper also provides a method for reducing the time taken by traditional HMAC functions and increases complexity of SHA-512.

1. Secure Hash Algorithm, Wikipedia (access on 10 January 2014) http://en. wikipedia. org/wiki/Secure_Hash_Algorithm
2. William Stallings, Cryptography and Network Security : Principles and Practice , fifth Edition, Prentice hall.
3. S. Gueron, S. Johnson and J. Walker, "SHA-512/256", IEEE Conference on IT:new Generations, pp. 354-358, 2011.
4. BigDecimal and BigInteger, Stackoverflow (access on 20 January 2014) http://stackoverflow. com/search?q=bigdecimal+and+biginteger
5. Java Optimization Rules, Appperfect (access on 22 January 2014) http://www. appperfect. com/support/java-coding-rules/optimization. html
6. A. Mandal and A. Tiwari, "Analysis of Avalanche Effect in Plaintext of DES using Binary codes", International Journal of Emerging Trnds and Technology in Computer Science, vol. 1 , pp. 166-171, 2012.
7. String Similarity test, Tools4noobs (access on 2 February 2014) http://www. tools4noobs. com/online_tools/String-similarity

HMAC SHA-512 Modified SHA-512 Avalanche effect Buffers.