Data Security

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hash function

part 1

1- what is the hash function

A Hash function (H) accepts a variable-length block of data M as input and produces a fixed-size hash value h = H(M).

2- what is the good hash function

A “good” hash function has the property that the results of applying the function to a large set of inputs will produce outputs that are evenly distributed and apparently random.

3- what is the principal object of a hash function

data integrity.

4- what is the Cryptographic hash function? and what is computationally infeasible to find?

is an algorithm for which it is computationally infeasible to find either (a) a data object that maps to a pre-specified hash result (the one-way property) or (b) two data objects that map to the same hash result (the collision-free property). Because of these characteristics, hash functions are often used to determine whether or not data has changed.

5-what is the Applications of Cryptographic Hash Functions:

(1) Message authentication,

(2) Digital Signature,

(3) One-way password file,

(4) Intrusion detection,

(5) Virus detection,