Sunday, 3 February 2013

Cryptographic Hash Function

A cryptographic hash function is a function that takes a message of any length as input and transforms into a fixed length output called a hash value, a message digest, a checksum or a digital fingerprint.

Properties of Cryptographic hash function

1. Cryptographic hash function accept a block of data of any size as input.
2. Cryptographic hash function produce a fixed length output independent of the message size.
3. Cryptographic hash function behaves like a random function.
4. Given a message digest it is very difficult to generate the message.

MD5 hash algorithm ,SHA(Secure Hash function) are examples of Cryptographic hash function.

Message digest produced by a MD5 hash function





Message digest produced by a SHA hash function





Message digest produced by a SHA hash function after changing a single character





Message digest produced by a  MD5 hash function after changing a single character






We can see that the hash value generated using MD5 and SHA are different for  the original and modified message.

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