10 - Lecture #10 SS G513 Network Security Cryptography and...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture #10 SS G513 Network Security
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown
Background image of page 2
Chapter 11 – Message Authentication and Hash Functions At cats' green on the Sunday he took the message from the inside of the pillar and added Peter Moran's name to the two names already printed there in the "Brontosaur" code. The message now read: “Leviathan to Dragon: Martin Hillman, Trevor Allan, Peter Moran: observe and tail.” What was the good of it John hardly knew. He felt better, he felt that at last he had made an attack on Peter Moran instead of waiting passively and effecting no retaliation. Besides, what was the use of being in possession of the key to the codes if he never took advantage of it? Talking to Strange Men, Ruth Rendell
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Secure Hash Algorithm (SHA-1) SHA was designed by NIST & NSA in 1993, revised 1995 as SHA-1 US standard for use with DSA signature scheme standard is FIPS 180-1 1995, also Internet RFC3174 nb. the algorithm is SHA, the standard is SHS produces 160-bit hash values now the generally preferred hash algorithm based on design of MD4 with key differences
Background image of page 4
SHA Overview 1. pad message so its length is 448 mod 512 2. append a 64-bit length value to message 3. initialise 5-word (160-bit) buffer (A,B,C,D,E) to (67452301,efcdab89,98badcfe,10325476,c3d2e1f0) 1. process message in 16-word (512-bit) chunks: expand 16 words into 80 words by mixing & shifting use 4 rounds of 20 bit operations on message block & buffer add output to input to form new buffer value 2. output hash value is the final buffer value
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
SHA-1 Compression Function each round has 20 steps which replaces the 5 buffer words thus: (A,B,C,D,E) <-(E+f(t,B,C,D)+(A<<5)+W t +K t ),A, (B<<30),C,D) a,b,c,d refer to the 4 words of the buffer t is the step number f(t,B,C,D) is nonlinear function for round W t is derived from the message block K t is a constant value derived from sin
Background image of page 6
SHA-1 Compression Function
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
SHA-1 verses MD5 brute force attack is harder (160 vs 128 bits for MD5) not vulnerable to any known attacks (compared to MD4/5) a little slower than MD5 (80 vs 64 steps) both designed as simple and compact optimised for big endian CPU's (vs MD5 which is optimised for little endian CPU’s)
Background image of page 8
Revised Secure Hash Standard NIST have issued a revision FIPS 180-2 adds 3 additional hash algorithms SHA-256, SHA-384, SHA-512 designed for compatibility with increased security provided by the AES cipher hence analysis should be similar
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/14/2010 for the course CSE SS ZG513 taught by Professor Sundarb during the Summer '10 term at Birla Institute of Technology & Science.

Page1 / 35

10 - Lecture #10 SS G513 Network Security Cryptography and...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online