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Hash and MAC Algorithms-Computer And System Security-Lecture Slides, Slides of Cryptography and System Security

Ankit Institute of Technology and ScienceCryptography and System Security

This lecture was delivered by Dr. Samarendra Jeethesh at Ankit Institute of Technology and Science for System Security and Cryptography course. It includes: Hash, MAC, Algorithms, Functions, Message, Authentication, Code, Block, Cipher, Mode, Algorithm, Structure

Typology: Slides

2011/2012

Uploaded on 07/17/2012

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Chapter 12 – Hash and MAC
Algorithms
Each of the messages, like each one he had ever
read of Stern's commands, began with a number
and ended with a number or row of numbers. No
efforts on the part of Mungo or any of his experts
had been able to break Stern's code, nor was
there any clue as to what the preliminary
number and those ultimate numbers signified.
—Talking to Strange Men, Ruth Rendell
docsity.com
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Chapter 12 – Hash and MAC

Algorithms

Each of the messages, like each one he had ever read of Stern's commands, began with a numberand ended with a number or row of numbers. Noefforts on the part of Mungo or any of his expertshad been able to break Stern's code, nor wasthere any clue as to what the preliminarynumber and those ultimate numbers signified. — Talking to Strange Men, Ruth Rendell

Hash and MAC Algorithms

Hash Functions

 condense arbitrary size message to fixed size  by processing message in blocks  through some compression function  either custom or block cipher based 

Message Authentication Code (MAC)

 fixed sized authenticator for some message  to provide authentication for message  by using block cipher mode or hash function

Secure Hash Algorithm

 SHA originally designed by NIST & NSA in 1993  was revised in 1995 as SHA-  US standard for use with DSA signature scheme  standard is FIPS 180-1 1995, also Internet RFC  nb. the algorithm is SHA, the standard is SHS  based on design of MD4 with key differences  produces 160-bit hash values  recent 2005 results on security of SHA-1 haveraised concerns on its use in future applications

Revised Secure Hash

Standard

NIST issued revision FIPS 180-2 in 2002

adds 3 additional versions of SHA

SHA-256, SHA-384, SHA-

designed for compatibility with increasedsecurity provided by the AES cipher

structure & detail is similar to SHA-

hence analysis should be similar

but security levels are rather higher

SHA-512 Compression

Function

heart of the algorithm

processing message in 1024-bit blocks

consists of 80 rounds

 updating a 512-bit buffer  using a 64-bit value Wt derived from thecurrent message block  and a round constant based on cube root offirst 80 prime numbers

SHA-512 Round Function

Whirlpool

now examine the Whirlpool hash function

endorsed by European NESSIE project

uses modified AES internals ascompression function

addressing concerns on use of blockciphers seen previously

with performance comparable to dedicatedalgorithms like SHA

Whirlpool Overview

Whirlpool Block Cipher W

Whirlpool Performance &

Security

Whirlpool is a very new proposal

hence little experience with use

but many AES findings should apply

does seem to need more h/w than SHA,but with better resulting performance

HMAC

 specified as Internet standard RFC  uses hash function on the message: HMAC K = Hash[(K

XOR opad) || Hash[(K

XOR ipad)||M)]]  where K

is the key padded out to size  and opad, ipad are specified padding constants  overhead is just 3 more hash calculations thanthe message needs alone  any hash function can be used  eg. MD5, SHA-1, RIPEMD-160, Whirlpool

HMAC Overview

CMAC

previously saw the DAA (CBC-MAC)

widely used in govt & industry

but has message size limitation

can overcome using 2 keys & padding

thus forming the Cipher-based MessageAuthentication Code (CMAC)

adopted by NIST SP800-38B

CMAC Overview