criptografia, Apuntes de Didáctica General

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DATA AND COMPUTER COMMUNICATIONS, EIGHTH EDITION

A comprehensive survey that has become the standard in the field, covering

(1) data communications, including transmission, media, signal encoding, link

control, and multiplexing; (2) communication networks, including circuit- and

packet-switched, frame relay, ATM, and LANs; (3) the TCP/IP protocol suite,

including IPv6, TCP, MIME, and HTTP, as well as a detailed treatment of

network security. Received the 2007 Text and Academic Authors Association

(TAA) award for the best Computer Science and Engineering Textbook of the

year. ISBN 0-13-243310-

COMPUTER ORGANIZATION AND ARCHITECTURE,

EIGHTH EDITION

A unified view of this broad field. Covers fundamentals such as CPU, control

unit, microprogramming, instruction set, I/O, and memory. Also covers

advanced topics such as RISC, superscalar, and parallel organization. Fourth

and fifth editions received the TAA award for the best Computer Science and

Engineering Textbook of the year. ISBN 978-0-13-607373-

OPERATING SYSTEMS, SIXTH EDITION

A state-of-the art survey of operating system principles. Covers fundamental

technology as well as contemporary design issues, such as threads,

microkernels, SMPs, real-time systems, multiprocessor scheduling, embedded

OSs, distributed systems, clusters, security, and object-oriented design.

Received the 2009 Text and Academic Authors Association (TAA) award

for the best Computer Science and Engineering Textbook of the year.

ISBN 978-0-13-600632-

BUSINESS DATA COMMUNICATIONS, SIXTH EDITION

A comprehensive presentation of data communications and

telecommunications from a business perspective. Covers voice, data, image,

and video communications and applications technology and includes a number

of case studies. ISBN 978-0-13-606741-

COMPUTER NETWORKS WITH INTERNET PROTOCOLS

AND TECHNOLOGY

An up-to-date survey of developments in the area of Internet-based protocols

and algorithms. Using a top-down approach, this book covers applications,

transport layer, Internet QoS, Internet routing, data link layer and computer

networks, security, and network management. ISBN 0-13141098-

THE WILLIAM STALLINGS BOOKS ON COMPUTER

CRYPTOGRAPHY AND

NETWORK SECURITY

PRINCIPLES AND PRACTICE

FIFTH EDITION

William Stallings

Prentice Hall Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo

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If you purchased this book within the United States or Canada you should be aware that it has been wrongfully imported without the approval of the Publisher or the Author.

Copyright © 2011, 2006 Pearson Education, Inc., publishing as Prentice Hall. All rights reserved. Manufactured in the United States of America.This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise.To obtain permission(s) to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, 1 Lake Street, Upper Saddle River, NY 07458

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10 9 8 7 6 5 4 3 2 1

ISBN 10: 0-13-609704- ISBN 13: 978-0-13-609704-

Library of Congress Cataloging-in-Publication Data On File

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CONTENTS

Notation xiii

Preface xv

x CONTENTS

20.3 Password Management 20.4 Recommended Reading and Web Sites 20.5 Key Terms, Review Questions, and Problems Appendix 20A The Base-Rate Fallacy

Chapter 21 Malicious Software

21.1 Types of Malicious Software 21.2 Viruses 21.3 Virus Countermeasures 21.4 Worms 21.5 Distributed Denial of Service Attacks 21.6 Recommended Reading and Web Sites 21.7 Key Terms, Review Questions, and Problems

Chapter 22 Firewalls

22.1 The Need for Firewalls 22.2 Firewall Characteristics 22.3 Types of Firewalls 22.4 Firewall Basing 22.5 Firewall Location and Configurations 22.6 Recommended Reading and Web Sites 22.7 Key Terms, Review Questions, and Problems

PART SEVEN LEGAL AND ETHICAL ISSUES

Chapter 23 Legal and Ethical Issues

23.1 Cybercrime and Computer Crime 23.2 Intellectual Property 23.3 Privacy 23.4 Ethical Issues 23.5 Recommended Reading and Web Sites 23.6 Key Terms, Review Questions, and Problems

ONLINE APPENDICES WilliamStallings.com/Crypto/Crypto5e.html

Appendix C Sage Problems

C.1 Getting Started with Sage C.2 Programming with Sage C.3 Chapter 2: Classical Encryption Techniques C.4 Chapter 3: Block Ciphers and the Data Encryption Standard C.5 Chapter 4: Basic Concepts in Number Theory and Finite Fields C.6 Chapter 5:Advanced Encryption Standard C.7 Chapter 7: Pseudorandom Number Generation and Stream Ciphers C.8 Chapter 8: Number Theory C.9 Chapter 9: Public-Key Cryptography and RSA C.10 Chapter 10: Other Public-Key Cryptosystems C.11 Chapter 11: Cryptographic Hash Functions C.12 Chapter 13: Digital Signatures

CONTENTS xi

Appendix D Standards and Standards-Setting Organizations

D.1 The Importance of Standards D.2 Internet Standards and the Internet Society D.3 National Institute of Standards and Technology

Appendix E Basic Concepts from Linear Algebra

E.1 Operations on Vectors and Matrices E.2 Linear Algebra Operations over Zn

Appendix F Measures of Security and Secrecy

F.1 Perfect Secrecy F.2 Information and Entropy F.3 Entropy and Secrecy

Appendix G Simplified DES

G.1 Overview G.2 S-DES Key Generation G.3 S-DES Encryption G.4 Analysis of Simplified DES G.5 Relationship to DES

Appendix H Evaluation Criteria for AES

H.1 The Origins of AES H.2 AES Evaluation

Appendix I More on Simplified AES

I.1 Arithmetic in GF(2^4 ) I.2 The Mix Column Function

Appendix J Knapsack Public-Key Algorithm

J.1 The Knapsack Problem J.2 The Knapsack Cryptosystem J.3 Example

Appendix K Proof of the Digital Signature Algorithm

Appendix L TCP/IP and OSI

L.1 Protocols and Protocol Architectures L.2 The TCP/IP Protocol Architecture L.3 The Role of an Internet Protocol L.4 IPv L.5 IPv L.6 The OSI Protocol Architecture

Appendix M Java Cryptographic APIs

M.1 Introduction M.2 JCA and JCE Architecture M.3 JCA Classes M.4 JCE Classes M.5 Conclusion and References

NOTATION

Symbol Expression Meaning D, K D 1 K , Y 2 Symmetric decryption of ciphertext Y using secret key K

D, PRa D 1 PRa , Y 2 Asymmetric decryption of ciphertext Y using A’s private key PRa D, PUa D 1 PUa , Y 2 Asymmetric decryption of ciphertext Y using A’s public key PUa

E, K E 1 K , X 2 Symmetric encryption of plaintext X using secret key K E, PRa E( PRa , X ) Asymmetric encryption of plaintext X using A’s private key PRa

E, PUa E( PUa , X ) Asymmetric encryption of plaintext X using A’s public key PUa K Secret key

PRa Private key of user A PUa Public key of user A

MAC, K MAC( K, X )^ Message authentication code of message X using secret key K GF( p ) The finite field of order^ , where^ is prime. The field is defined as the set Z p together with the arithmetic operations modulo p.

p p

GF(2 n ) The finite field of order 2 n

Zn Set of nonnegative integers less than^ n

gcd gcd( i , j ) Greatest common divisor; the largest positive integer that divides both i and j with no remainder on division. mod a mod m Remainder after division of a by m

mod, K (^) a K b (mod m ) a mod m = b mod m

mod, [ (^) a [ b (mod m ) a mod m Z b mod m dlog (^) dlog a , p ( b ) Discrete logarithm of the number b for the base a (mod p ) w (^) f( n ) The number of positive integers less than and relatively prime to. This is Euler’s totient function.

n n

© a

n i = 1

ai a 1 + a 2 + Á^ + an

ß (^) q

n i = 1

ai a 1 * a 2 * Á (^) * an

Even the natives have difficulty mastering this peculiar vocabulary. — The Golden Bough, Sir James George Frazer

xiii

xiv NOTATION

| i | j i^ divides , which means that there is no remainder when^ is divided by i

j j

|, | | a | Absolute value of^ a

|| x || y x concatenated with^ y L x L y x is approximately equal to y

 x^  y^

Exclusive-OR of and for single-bit variables; Bitwise exclusive-OR of x and y for multiple-bit variables

x y

:,; : x ; The largest integer less than or equal to^ x  (^) x  S The element x is contained in the set S.

· Á , ak 2

A · ( a 1 , a 2 , The integer A corresponds to the sequence of integers ( a 1 , a 2 , Á , ak )

xvi PREFACE

material in IAS2 Security Mechanisms, a core area in the Information Technology body of knowledge; NET4 Security, another core area in the Information Technology body of knowl- edge; and IT311, Cryptography, an advanced course; these subject areas are part of the ACM/IEEE Computer Society Computing Curricula 2005. The book also serves as a basic reference volume and is suitable for self-study.

PLAN OF THE BOOK

The book is divided into seven parts (see Chapter 0 for an overview):

• Symmetric Ciphers
• Asymmetric Ciphers
• Cryptographic Data Integrity Algorithms
• Mutual Trust
• Network and Internet Security
• System Security
• Legal and Ethical Issues

The book includes a number of pedagogic features, including the use of the computer algebra system Sage and numerous figures and tables to clarify the discussions. Each chapter includes a list of key words, review questions, homework problems, suggestions for further reading, and recommended Web sites. The book also includes an extensive glossary, a list of frequently used acronyms, and a bibliography. In addition, a test bank is available to instructors.

ONLINE DOCUMENTS FOR STUDENTS

For this new edition, a tremendous amount of original supporting material has been made available online, in the following categories.

• Online chapters: To limit the size and cost of the book, four chapters of the book are provided in PDF format. This includes three chapters on computer security and one on legal and ethical issues. The chapters are listed in this book’s table of contents.
• Online appendices: There are numerous interesting topics that support material found in the text but whose inclusion is not warranted in the printed text. A total of fifteen online appendices cover these topics for the interested student. The appen- dices are listed in this book’s table of contents.
• Homework problems and solutions: To aid the student in understanding the material, a separate set of homework problems with solutions are available. These enable the students to test their understanding of the text.
• Key papers: Twenty-four papers from the professional literature, many hard to find, are provided for further reading.
• Supporting documents: A variety of other useful documents are referenced in the text and provided online.
• Sage code: The Sage code from the examples in Appendix B in case the student wants to play around with the examples.

PREFACE xvii

Purchasing this textbook now grants the reader six months of access to this online material. See the access card bound into the front of this book for details.

INSTRUCTIONAL SUPPORT MATERIALS

To support instructors, the following materials are provided:

• Solutions Manual: Solutions to end-of-chapter Review Questions and Problems.
• Projects Manual: Suggested project assignments for all of the project categories listed below.
• PowerPoint Slides: A set of slides covering all chapters, suitable for use in lecturing.
• PDF Files: Reproductions of all figures and tables from the book.
• Test Bank: A chapter-by-chapter set of questions.

All of these support materials are available at the Instructor Resource Center (IRC) for this textbook, which can be reached via personhighered.com/stallings or by clicking on the button labeled “Book Info and More Instructor Resources” at this book’s Web Site WilliamStallings.com/Crypto/Crypto5e.html. To gain access to the IRC, please contact your local Prentice Hall sales representative via pearsonhighered.com/ educator/replocator/requestSalesRep.page or call Prentice Hall Faculty Services at 1-800-526-0485.

INTERNET SERVICES FOR INSTRUCTORS AND STUDENTS

There is a Web site for this book that provides support for students and instructors. The site includes links to other relevant sites, transparency masters of figures and tables in the book in PDF (Adobe Acrobat) format, and PowerPoint slides. The Web page is at WilliamStallings.com/Crypto/Crypto5e.html. For more information, see Chapter 0. New to this edition is a set of homework problems with solutions available at this Web site. Students can enhance their understanding of the material by working out the solutions to these problems and then checking their answers. An Internet mailing list has been set up so that instructors using this book can exchange information, suggestions, and questions with each other and with the author. As soon as typos or other errors are discovered, an errata list for this book will be available at WilliamStallings.com. In addition, the Computer Science Student Resource site at WilliamStallings.com/StudentSupport.html provides documents, information, and useful links for computer science students and professionals.

PROJECTS AND OTHER STUDENT EXERCISES

For many instructors, an important component of a cryptography or security course is a pro- ject or set of projects by which the student gets hands-on experience to reinforce concepts from the text. This book provides an unparalleled degree of support, including a projects component in the course. The IRC not only includes guidance on how to assign and structure