Research paper on SHA2 algorithm of minimum 20 pages

In general the SHA2 algorithm ( secure hash algorithm ) is a combination of cryptographic hash functions designed by the united states national security agency (NSA) . Actually cryptographic hash functions are mathematical operations which are run on digital data just by comparing the computed hash ( this is nothing but the output that which we get by executing the algorithm ). In general cases SHA 2 is not often used as of now and even it is the successor of SHA1 and gathered 4 kinds of hash functions such as the SHA224, SHA384, and SHA512. even it works in the same way than SHA1 but is stronger and generate a longer hash.