[...]...Foreword As a companion book of Vaudenay's A Classical Introduction to Cryptography, this exercise book contains a carefully revised version of most of the material used in teaching by the authors or given as examinations to the undergraduate students of the Cryptography and Security lecture at EPFL from 2000 to mid-2005 It covers a majority of the subjects that make up today's cryptology, such as symmetric... What is the probability that C*(x) = y? Let K E (0,l)' be a random Figure 2.2 A cascade of L block ciphers 24 EXERCISE BOOK variable Assuming that EK roughly behaves like C*, compute an estimation of the amount of wrong keys displayed by Algorithm 2 How many wrong keys are displayed for a similar algorithm on a cascade of L ciphers? Assume that the adversary knows t plaintext/ciphertext pairs, all... A Classical Introduction to Cryptography, exercises related to the more advanced parts of the textbook are marked with a star The difficulty of the exercises covers a broad spectrum In some the student is expected to simply apply basic facts, while in others more intuition and reflexion will be necessary to find the solution Nevertheless, the solutions accompanying the exercises have been written as... investigates basic facts of modern symmetric cryptography, focusing on the Data Encryption Standard, modes of operations, and stream ciphers Chapter 3 handles the hash functions topic, while Chapter 4 describes some more involved notions of cryptanalysis of block ci- xiv EXERCISE BOOK phers Chapter 5 considers protocols based on symmetric cryptography Chapter 6 is based on some basic facts of algebra and... signatures Chapter 11 exposes some protocols using public-key cryptography, and Chapter 12 handles the case of hybrid protocols, combining both symmetric and public-key schemes A website (http://www intro -to- crypto inf o) has been set up as a companion of this book It will contain inevitable errata as well as other material related to this book, like challenging tests and more exercises Finally, the authors... public-key cryptography, cryptographic protocols, design, cryptanalysis, and implementation of cryptosystems Exercises do not require a large background in mathematics, since the most important notions are introduced and discussed in many of the exercises We expect the readers to be comfortable with basic facts of discrete probability theory, discrete mathematics, calculus, algebra, as well as computer... Explain how a smart choice of x and x' allows us to detect that we have u4 = uh and v = v simultaneously (here uh and vi are the internal q h intermediate values for computing y') 8 Use the previous question to mount a chosen plaintext attack whose goal is to find a (x, x') pair with u4 = u&and v4 = vi simultaneously What is the complexity of this attack? 9 Explain how to use this attack in order to. .. and an electric connection which represents a permutation on {a, b, c , ,z) with 14 fixed points and 6 non-overlapping exchanges of two characters For example, v, lets a, c, d, f ,j , l,n , o, r, u, w, x, y unchanged, maps b to t and t to b, e to q and q to e, etc A toy Enigma machine (limited to 6 letters) is represented in Figure 1.3 Lampboard Kevboard Plugboard Rotor 1 Rotor 2 Rotor 3 Reflector... weight, we have found a counterexample Finally, as a transposition is a particular permutation which simply rearranges the bits of an input string, it should be clear that a transposition preserves the Hamming weight -' 8 Yes Formally, we recall that a permutation P on (0, lIe is a bijection from (0, lIe to (0, lie We also give the definition of a transposition thereafter, in a formal way Let T : (0,... a meet-in-the-middle attack Give an approximate of the time and memory complexities 2 Two-Key 3DES encrypts a 64-bit message M in the following manner Here, K1 and K2 are strings of 56 bits each (a) What is the average complexity of a "naive" exhaustive search? (b) We are given a box that encrypts a message M according to (2.1) We may use the box to encrypt plaintexts of our choice Denoting 0 the all-zero . class="bi x0 y0 w1 h1" alt="" A CLASSICAL INTRODUCTION TO CRYPTOGRAPHY EXERCISE BOOK A CLASSICAL INTRODUCTION TO CRYPTOGRAPHY EXERCISE BOOK Thomas Baignkres EPFL, Switzerland Pascal. Congress Cataloging-in-Publication Data A C.I.P. Catalogue record for this book is available from the Library of Congress. A CLASSICAL INTRODUCTION TO CRYPTOGRAPHY EXERCISE BOOK by Thomas Baignkres,. - I&C - LASEC Lausanne, Switzerland Pascal Junod Lausanne, Switzerland Jean Monnerat EPFL-I&C-LASEC Lausanne, Switzerland Serge Vaudenay Lausanne, Switzerland Library of