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Hash Function

Overview#

Hash Function is a deterministic function that takes an arbitrary block of data, the Message and returns a fixed-size bit string, the Hash value, such that an accidental or intentional change to the data will almost certainly change the Hash.

Hash Function Message-Digest, or Fingerprint

In our contexts, the data to be encoded is called the Message, and the hash value is called the Hash.

A Cryptographic Hash Function is a Hash Function with some additional properties.

Hash Functions may be used for the mapping function used in accessing hash tables, a data structure used in many algorithms.
These Hash Functions may not be suitable Cryptographic Hash Function as they do not have Hash Function Security Properties.

Why Hash Function?#

Given a message m, you could sign the message itself. Public Key operations of most Digital Signature Algorithms are fairly CPU expensive in computational terms. If a Hash Function is applied to the message first and then use Digital Signature to sign the Hash instead.

More Information#

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