Rather than just shifting the alphabet Could shuffle (jumble) the letters arbitrarily Each plaintext letter maps to a different random cipher text letter.

Slides:

Advertisements

Similar presentations

Crypto for CTFs RPISEC 2013 Ben Kaiser. Terminology plaintext - the original message ciphertext - the coded message cipher - algorithm for transforming.

Advertisements

Cryptography and Network Security Chapter 2

Cryptography and Network Security Chapter 2. Chapter 2 – Classical Encryption Techniques Many savages at the present day regard their names as vital parts.

Announcement Grading adjusted –10% participation and two exams 20% each Newsgroup up Assignment upload webpage up Homework 1 will be released over the.

CSCE 790G: Computer Network Security

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

Classical Encryption Techniques Lecture slides adapted from Lawrie Brown 1.

Chapter 2 – Classical Encryption Techniques. Classical Encryption Techniques Symmetric Encryption Or conventional / private-key / single-key sender and.

Classical Encryption Techniques

Review What is security: history and definition Security policy, mechanisms and services Security models.

Announcements: Homework 1 coming Monday… Homework 1 coming Monday… Practical quiz during week 4 on putting your code to work Practical quiz during week.

Classical Encryption Techniques

CSE 651: Introduction to Network Security

Overview of Cryptographic Techniques Hector M Lugo-Cordero CIS 4361 Secure Operating System Administration 1.

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

Classical Monoalphabetic Ciphers Day 2. Keyword cipher Select a keyword, if the keyword has any repeated letters, drop all but the first occurrence. Write.

Classical Encryption Techniques

Cryptography. Secret (crypto) Writing (graphy) –[Greek word] Practice and study of hiding information Concerned with developing algorithms for: –Conceal.

Cryptography and Network Security Chapter 2. Chapter 2 – Classical Encryption Techniques Many savages at the present day regard their names as vital parts.

A Technical Seminar Presentation CLASSICAL CRYPTOGRAPHY

Dr. Lo’ai Tawalbeh 2007 Chapter 2: Classical Encryption Techniques Dr. Lo’ai Tawalbeh New York Institute of Technology (NYIT) Jordan’s Campus INCS.

1 University of Palestine Information Security Principles ITGD 2202 Ms. Eman Alajrami 2 nd Semester

Chapter 2 Classical Encryption Techniques. Symmetric Encryption n conventional / private-key / single-key n sender and recipient share a common key n.

Hill Cipher Developed by the mathematician Lester Hill in The encryption algorithm takes m successive plain text and substitute for them m cipher.

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

Computer Science&Technology School of Shandong University Instructor: Hou Mengbo houmb AT sdu.edu.cn Office: Information Security Research Group.

Cryptography and Network Security Chapter 2. Symmetric Encryption  or conventional / private-key / single-key  sender and recipient share a common key.

Cryptography and Network Security (CS435) Part Two (Classic Encryption Techniques)

Cryptography and Network Security Chapter 2 Fourth Edition by William Stallings Lecture slides by Lawrie Brown.

Symmetric Encryption or conventional / private-key / single-key sender and recipient share a common key all classical encryption algorithms are private-key.

Network Security Lecture 12 Presented by: Dr. Munam Ali Shah.

Classical Encryption Techniques CSE 651: Introduction to Network Security.

 Classic Crypto  Slides based on those developed by Dr. Lawrie Brown at the Australian Defence Force Academy, University College, UNSW  See

Classic Cryptography History. Some Basic Terminology plaintext - original message ciphertext - coded message cipher - algorithm for transforming plaintext.

1 University of Palestine Information Security Principles ITGD 2202 Ms. Eman Alajrami.

CSCI-100 Introduction to Computing Privacy & Security Part II.

Introduction to Ciphers Breno de Medeiros. Cipher types From “Cipher”, Wikipedia article.

Computer and Network Security Rabie A. Ramadan Lecture 2.

Data Security and Encryption (CSE348) 1. Lecture # 4 2.

1 Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown [Changed by Somesh Jha]

1 Cryptography and Network Security Fourth Edition by William Stallings Lecture slides by Lawrie Brown [Changed by Somesh Jha]

Information Systems Security 3. Chapter 2 – Classical Encryption Techniques Many savages at the present day regard their names as vital parts of themselves,

Chapter 2 – Classical Encryption Techniques. Symmetric Encryption or conventional / private-key / single-key sender and recipient share a common key all.

Chapter 2 – Classical Encryption Techniques Many savages at the present day regard their names as vital parts of themselves, and therefore take great pains.

Instructor: Dania Alomar

1 Cryptography and Network Security Fourth Edition by William Stallings Lecture slides by Lawrie Brown [Changed by Somesh Jha]

Cryptography and Network Security Chapter 2 Fifth Edition by William Stallings Lecture slides by Lawrie Brown.

1 Classical Encryption Techniques. 2 Symmetric cipher model –Cryptography –Cryptanalysis Substitution techniques –Caesar cipher –Monoalphabetic cipher.

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

By Marwan Al-Namari & Hafezah Ben Othman Author: William Stallings College of Computer Science at Al-Qunfudah Umm Al-Qura University, KSA, Makkah 1.

Cryptography and Network Security Third Edition by William Stallings Lecture slides by Lawrie Brown.

Prof. Wenguo Wang Network Information Security Prof. Wenguo Wang Tel College of Computer Science QUFU NORMAL UNIVERSITY.

Cryptography and Network Security Chapter 2 Fifth Edition by William Stallings Lecture slides by Lawrie Brown.

CSEN 1001 Computer and Network Security Amr El Mougy Mouaz ElAbsawi.

@Yuan Xue CS 285 Network Security Cryptography Overview and Classical Encryption Algorithms Fall 2012 Yuan Xue.

CS480 Cryptography and Information Security Huiping Guo Department of Computer Science California State University, Los Angeles 4. Traditional and Modern.

@Yuan Xue Quick Review.

CRYPTOGRAPHY G REEK WORD MEANING “ SECRET WRITING ”

BINF 711 Amr El Mougy Alaa Gohar. Lecture (2) Cryptographic Tools.

Part 2 By Dr. Shadi Masadeh

Communication Security

Classical Polygraphic Ciphers

Cryptography and Network Security

Lecture Classical Encryption Techniques Dr. Nermin Hamza

CS4780 Cryptography and Information Security

Substitution Ciphers.

Outline Some Basic Terminology Symmetric Encryption

Computer and Network Security

Presentation transcript:

Rather than just shifting the alphabet Could shuffle (jumble) the letters arbitrarily Each plaintext letter maps to a different random cipher text letter hence key is 26 letters long Plain: abcdefghijklmnopqrstuvwxyz Cipher: DKVQFIBJWPESCXHTMYAUOLRGZN Plaintext: ifwewishtoreplaceletters Cipher text: WIRFRWAJUHYFTSDVFSFUUFYA Monoalphabetic Cipher

Monoalphabetic Cipher Security Now have a total of 26! keys With so many keys, might think the system is secure But would be !!!WRONG!!! Problem is the regularities of the language

Language Redundancy and Cryptanalysis Human languages are redundant Letters are not equally commonly used The English letter e is by far the most common letter Then T,R,N,I,O,A,S Other letters are fairly rare Z,J,K,Q,X

English Letter Frequencies

Use in Cryptanalysis Key concept - monoalphabetic substitution ciphers do not change relative letter frequencies Discovered by Arabian scientists in 9 th century Calculate letter frequencies for ciphertext compare counts against known values

Example Cryptanalysis Given ciphertext: UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMETSXAIZ VUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZUHSX EPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ Count relative letter frequencies (see text) The most common letters are P & Z and are equivalent to e and t The most common Digram are ZW is equivalent to th and hence ZWP is the Proceeding with trial and error finally get: it was disclosed yesterday that several informal but direct contacts have been made with political representatives of the viet cong in moscow

Playfair Cipher Not even the large number of keys in a monoalphabetic cipher provides security One approach to improving security was to encrypt multiple letters The Playfair Cipher is an example Invented by Charles Wheatstone in 1854, but named after his friend Baron Playfair

Playfair Key Matrix A 5X5 matrix of letters based on a keyword Fill in letters of keyword Fill rest of matrix with other letters eg. using the keyword MONARCHY MONAR CHYBD EFGI/JK LPQST UVWXZ

Encrypting and Decrypting plaintext encrypted two letters at a time: – if a pair is a repeated letter, insert a filler like 'X', eg. "balloon" encrypts as "ba lx lo on" – if both letters fall in the same row, replace each with letter to right (wrapping back to start from end), eg. “ar" encrypts as "RM" – if both letters fall in the same column, replace each with the letter below it (again wrapping to top from bottom), eg. “mu" encrypts to "CM" – otherwise each letter is replaced by the one in its row in the column of the other letter of the pair, eg. “hs" encrypts to "BP", and “ea" to "IM" or "JM"

Security of the Playfair Cipher security much improved over monoalphabetic since have 26 x 26 = 676 digrams would need a 676 entry frequency table to analyse (verses 26 for a monoalphabetic) and correspondingly more ciphertext was widely used for many years (eg. US & British military in WW1) it can be broken, given a few hundred letters since still has much of plaintext structure

Hill Cipher Developed by the mathematician Lester Hill in The encryption algorithm takes m successive plain text and substitute for them m cipher text letters. Each character is assigned a numerical value (a=0,…z=25).