Hash Essay

756 Words2 Pages

Name:- Lochan KC
Course:- ICT4845
Paper # :- 2
Date:- 4/12/2014
Tiger: A Fast New Hash Function

The article is about new type of cryptographic hash function called Tiger developed by Ross Anderson and Eli Biham. It is designed to provide strong and fast hash function. The authors claims that it is as fast as SHA-1 on 32 bit processors and three times faster on 64 bit processors[1].The motivation for the development of tiger came from the fact that collision attacks for Senfru and MD4 was found and also due to poor performance of these functions on 64 bit processors. The author considers the following design criteria for tiger:-it has to be secure with collision and multiplication free, optimized for 64 bit processors and easy replacement for MD4, MD5,SHA and SHA-1[1].
The Tiger hash function produces 192 bit hash value from 512 bit message block. The main operation consists of 4 S-boxes that maps 8 bit to 64 bits, 64 bit addition, subtraction and multiplication and a key schedule for generating 24 rounds of key. To compatible with MD4 and SHA, the output from hash value can be also truncated to 128 and 160 bit. To avoid from intermediate stage attack, it uses large intermediate hash values. It uses three 64 bit registers a, b and c for intermediate hash values. Also each 512 bit blocks is divided into 8 , 64 bits words. It consists of the following stages:- save_abc, pass(a,b,c,5), key_schedule, pass(c,a,b,7),key _schedule, pass(b,c,a,9) and feedforward. Save_abc saves the initial value so that it will be used later on feedforward.Each pass consists of 8 rounds and uses multiplier of 5 ,7 and 9 to redistribute bits between s-box lookups. The round function will then generate new values using the following algorithm. c^=x; ...

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...cation and longer Intermediate blocks provides Tiger strong avalanche effect and resistance to shortcut and Dobbertin's differential attacks. But in the recent cryptanalysis of Tiger hash function, the collision attacks were found .

Biblography
1. Anderson, Ross, and Eli Biham. "Tiger: A fast new hash function." In Fast Software Encryption, pp. 89-97. Springer Berlin Heidelberg, 1996.
2. Stallings, William. "3.2 / Secure Hash Functions." Network Security Essentials: Applications and Standards. Boston, MA: Pearson, 2012. 61-70. Print.
3. Florian Mendel and Vincent Rijmen. 2007. Cryptanalysis of the tiger hash function. InProceedings of the Advances in Crypotology 13th international conference on Theory and application of cryptology and information security (ASIACRYPT'07), Kaoru Kurosawa (Ed.). Springer-Verlag, Berlin, Heidelberg, 536-550.

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