程序代写代做代考 algorithm Introduction to Computer Security – G6077

Introduction to Computer Security – G6077
Dr. Imran U Khan Engineering and Informatics Sussex University
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Overview
Introduction and checksum method Key characteristics
General design of hashing algorithms Popular hashing algorithms Applications of hashing
Salting hashing
 Collisions 

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Introduction and checksum method
 Cryptography is to provide privacy, prove identity and show integrity
 Secret key used to provide secrecy/privacy but we need a method to check integrity of a message
 Hashing used either to hide the original contents of a message or to check the integrity of data
 In the past, checksum method used to check integrity of data e.g.
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Adding a value to list of number so that the total would be a multiple of 9
If 4, 5 and 13 were to be sent 4+5+13 = 22
What number shall we add to 22 to get a multiple of 9? Ans: 5 (22+5=27)
The following values/data will be rejected e.g.
4+5+13 with a checksum of 8
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Will provide 30 (4+5+13+8(cs)) which is not a multiple of 9
 Hashing methods /functions: a mathematical function that converts a numerical input value into another compressed numerical value
 Input to the function varied in length but output is always of fixed length
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

 Returned values are called hash values or message digest
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Key characteristics of Hash functions
 Must be hard to retrieve the original text from the hash value
 Must be hard to find two different inputs of any length that result in the same hash. In other words, for a hash function h, it is hard to find any two different inputs x and y such that h(x) = h(y)
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

General design of hashing algorithms
 Function operates on two fixed-size blocks
 Block size varies depends on the algorithm, 128 bits to
512 bits
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

 Hashing algorithm involves rounds of above hash function like a block cipher
 Each round takes an input of fixed size of message block and output of the last round
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Popular Hash functions
Message Digest (MD)
MD2, MD4, MD5 and MD6
128-bit hash function
MD5 most popular, widely used hash function
In 2004 collisions were found in MD5
Analytical attack reported
MD5 is compromised and not recommended anymore
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Secure Hash Function (SHA)
Four SHA algorithms; SHA-0, SHA-1, SHA-2, and SHA-3 SHA-0: 160-bit, released in 93 by NIST
SHA-1: most popular and widely used, employed in
protocols including SSL (Secure Socket Layer), in 2005
method was found for uncovering collisions for SHA-1 SHA-2: SHA-224, SHA-256, SHA-384 and SHA-512, no
successful attack on SHA-2 variants, weakness of SHA- 2 is that it follows design principle of SHA-1
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

SHA-3: 2012, Keccak algorithm, offers efficient performance and stronger resistance for attacks
RIPEMD
RACE Integrity Primitives Evaluation Message Digest – known as European family of Hash functions
RIPEMD-128, RIPEMD-160, 256 and 320
Based on MD4 design principles, provide questionable
security
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Whirlpool
512-bit hash function Whirlpool-0 and Whirlpool-T Derived from AES
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Applications of Hashing
Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University

Dr. Imran U Khan, Lecturer (Teaching focused), Informatics Sussex University