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  • Topic: Cryptographic hash function, Hash function, Block cipher
  • Pages : 10 (3280 words )
  • Download(s) : 25
  • Published : January 10, 2013
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Introduction
In this digitized world, information became essential part in human’s life. Every where people are dealing with information and every field is linked with information which is analyzed, processed and stored in computer. Data is important part of decision making process. Any fault or delay in information can lead to drastic result which can unfavorable to human kind. More and more organizations and personal user wants their data to be processed fast and without an error. Hash Function is used for both that are securing data as well as locating the data fast. Hash function have important and very wide role in cryptography. With the help of hash function, hash values are generated who increases the length of the messages by padding the extra bits to the strings. Few example of hash functions are MD4, SHA-1, MD5. The major function of cryptographic hash is to provide integrity to the message and provision to check it by digital signature. In this report we analyzed hash function with propositional reasoning and i also tried to raise issues concerning hash function Background:

A cryptographic hash function is an algorithm which takes variable size block of data and stores a fixed size string. Encoded data is called ‘message’ and hash value is called as digest or message digest. Hash function is a one way cryptographic algorithm in this there is no need to send the key to the receiver with the message unlike other cryptographic methods using keys. Characteristics of cryptographic hash function:

* It is difficult to modify the message encrypted with hash function which helps to protect the integrity of the message. * It is easy to calculate hash value for data/information. * It is difficult to get two different information having same hash codes. * Difficult to produce message with given hash.

Algorithms of hash function are used for many security policies to protect the information by using security application like message authentication code (MAC), Digital signature and many more application for security of the information. There are some other application of hash function also like fingerprinting, file comparison and searching, detecting duplicate files, checksums -------------------------------------------------

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Properties:
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Cryptographic hash function algorithms are mostly designed to take input message variable length and produces output message with fixed length hash codes. These hash functions are used to protect the data from external vulnerabilities and attacks. For the protection from attacks, hash function posses some resistance policies to protect message. * Preimage resistance

When message is encoded with hash function it becomes very difficult to find message in the network to corrupt it. So this primarily eliminates the preimage attacks which are harmful to the integrity of the message. One way hash function uses this concept to protect the data.

* Second preimage resistance

With this property, it is very difficult to find different input when hashing is done to the message. This property is also known as weak collision resistance and it saves the message from second-preimaga attacks.

* Collision resistance

It becomes difficult to find two dissimilar messages and such duo is called hash collision. This property is also known as strong collision resistance. Length of the hash value in this resistance property is required as twice as with compared to the preimage resistance. This property of the hash function protects the data from birthday...
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