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HARSH FUNCTION (INFORMATION SECURITY)- SIR PRINCE DUAH MENSAH- MPhil IT
1. AKENTEN APPIAH- MENKAH UNIVERSITY OF SKILL TRAINING AND ENTREPRENEURIAL DEVELOPMENT
SECURE HASH FUNCTIONS
IN
INFORMATION SECURITY
BY
MILLICENTIA PRINCE DUAH MENSAH CALEB
2. AKENTEN APPIAH- MENKAH UNIVERSITY OF SKILL TRAINING AND ENTREPRENEURIAL DEVELOPMENT
What are Secure Hash Functions?
Secure Hash Functions, with the acronym SHA, are a family of
cryptographic hash functions used to create text signature or hash data
and certificates.
Secure Hash Functions take an input of 20 bytes (160 bits) long
maximum and returns a 40- digit hexadecimal hash value as its output.
The smallest changes in the input can make a big difference in the coded
text output. The phenomenon is called the Avalanche Effect
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Figure 1: Shows the Basic Concept of Secure Hash Functions
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Characteristics of Secure Hash Functions
They have variable input length and fixed output length
The are one- way functions
If the same input message is fed to the Secure Hash Function, it will
generate the same resultant hash.
It is not possible to generate the same hash value using two different
input values. This is called Collision Resistance
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Types of Secure Hash Functions
Some of the Secure Hash Functions currently in use are:
Secure Hash Algorithm (SHA)- 1
Secure Hash Algorithm (SHA)- 2
Secure Hash Algorithm (SHA)- 3
Because Secure Hash Algorithm- 1 is being phased out and is not recommended for
any new designs, this application note only discusses SHA- 2 and SHA- 3
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SECURE HASH ALGORITHM (SHA)- 2
The SHA- 2 function has four main types based on output bit lengths as
follows:
SHA-224 – hash is 224 bits long
SHA-256 – hash is 256 bits long
SHA-384 – hash is 384 bits long
SHA-512 – hash is 512 bits long
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Figure 2: Secure Hash Algorithm (SHA)- 2
(SHA-256 – hash generation flow)
The input message is first padded to make sure that it will completely fit in “n” number of
512-bit blocks.
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SECURE HASH ALGORITHM (SHA)- 3
The SHA-3 function has no predefined output length. The input and output lengths have no
maximums either. For comparison purposes with SHA-2, we can define four main types
based on output bit lengths:
SHA3-224 – hash is 224 bits long
SHA3-256 – hash is 256 bits long
SHA3-384 – hash is 384 bits long
SHA3-512 – hash is 512 bits long
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Figure 3: Secure Hash Algorithm- 3 (SHA3-256 – Keccak sponge hash generation flow)