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CRYPTOGRAPHY ANDNETWORK SECURITYPRINCIPLES AND PRACTICESEVENTH EDITIONGLOBAL EDITIONWilliam StallingsBoston Columbus Indianapolis New York San Francisco HobokenAmsterdam Cape Town Dubai London Madrid Milan Munich Paris Montréal TorontoDelhi Mexico City São Paulo Sydney Hong Kong Seoul Singapore Taipei TokyoHiva-Network.Com

CONTENTSNotation 10Preface 12About the Author 18PART ONE: BACKGROUND 19Chapter 1 Computer and Network Security Concepts 191.1Computer Security Concepts 211.2The OSI Security Architecture 261.3Security Attacks 271.4Security Services 291.5Security Mechanisms 321.6Fundamental Security Design Principles 341.7Attack Surfaces and Attack Trees 371.8A Model for Network Security 411.9Standards 431.10Key Terms, Review Questions, and Problems 44Chapter 2 Introduction to Number Theory 462.1Divisibility and the Division Algorithm 472.2The Euclidean Algorithm 492.3Modular Arithmetic 532.4Prime Numbers 612.5Fermat’s and Euler’s Theorems 642.6Testing for Primality 682.7The Chinese Remainder Theorem 712.8Discrete Logarithms 732.9Key Terms, Review Questions, and Problems 78Appendix 2A The Meaning of Mod 82PART TWO: SYMMETRIC CIPHERS 85Chapter 3 Classical Encryption Techniques 853.1Symmetric Cipher Model 863.2Substitution Techniques 923.3Transposition Techniques 1073.4Rotor Machines 1083.5Steganography 1103.6Key Terms, Review Questions, and Problems 112Chapter 4 Block Ciphers and the Data Encryption Standard 1184.1Traditional Block Cipher Structure 1194.2The Data Encryption Standard 1294.3A DES Example 1314.4The Strength of DES 1343

4CONTENTS4.5Block Cipher Design Principles 1354.6Key Terms, Review Questions, and Problems 137Chapter 5 Finite Fields 1415.1Groups 1435.2Rings 1455.3Fields 1465.4Finite Fields of the Form GF(p) 1475.5Polynomial Arithmetic 1515.6Finite Fields of the Form GF(2n) 1575.7Key Terms, Review Questions, and Problems 169Chapter 6 Advanced Encryption Standard 1716.1Finite Field Arithmetic 1726.2AES Structure 1746.3AES Transformation Functions 1796.4AES Key Expansion 1906.5An AES Example 1936.6AES Implementation 1976.7Key Terms, Review Questions, and Problems 202Appendix 6A Polynomials with Coefficients in GF(28) 203Chapter 7 Block Cipher Operation 2077.1Multiple Encryption and Triple DES 2087.2Electronic Codebook 2137.3Cipher Block Chaining Mode 2167.4Cipher Feedback Mode 2187.5Output Feedback Mode 2207.6Counter Mode 2227.7XTS-AES Mode for Block-Oriented Storage Devices 2247.8Format-Preserving Encryption 2317.9Key Terms, Review Questions, and Problems 245Chapter 8 Random Bit Generation and Stream Ciphers 2508.1Principles of Pseudorandom Number Generation 2528.2Pseudorandom Number Generators 2588.3Pseudorandom Number Generation Using a Block Cipher 2618.4Stream Ciphers 2678.5RC4 2698.6True Random Number Generators 2718.7Key Terms, Review Questions, and Problems 280PART THREE: ASYMMETRIC CIPHERS 283Chapter 9 Public-Key Cryptography and RSA 2839.1Principles of Public-Key Cryptosystems 2859.2The RSA Algorithm 2949.3Key Terms, Review Questions, and Problems 308

CONTENTSChapter 10 Other Public-Key Cryptosystems 31310.1Diffie-Hellman Key Exchange 31410.2Elgamal Cryptographic System 31810.3Elliptic Curve Arithmetic 32110.4Elliptic Curve Cryptography 33010.5Pseudorandom Number Generation Based on an Asymmetric Cipher 33410.6Key Terms, Review Questions, and Problems 336PART FOUR: CRYPTOGRAPHIC DATA INTEGRITY ALGORITHMS 339Chapter 11 Cryptographic Hash Functions 33911.1Applications of Cryptographic Hash Functions 34111.2Two Simple Hash Functions 34611.3Requirements and Security 34811.4Hash Functions Based on Cipher Block Chaining 35411.5Secure Hash Algorithm (SHA) 35511.6SHA-3 36511.7Key Terms, Review Questions, and Problems 377Chapter 12 Message Authentication Codes 38112.1Message Authentication Requirements 38212.2Message Authentication Functions 38312.3Requirements for Message Authentication Codes 39112.4Security of MACs 39312.5MACs Based on Hash Functions: HMAC 39412.6MACs Based on Block Ciphers: DAA and CMAC 39912.7Authenticated Encryption: CCM and GCM 40212.8Key Wrapping 40812.9Pseudorandom Number Generation Using Hash Functions and MACs 41312.10Key Terms, Review Questions, and Problems 416Chapter 13 Digital Signatures 41913.1Digital Signatures 42113.2Elgamal Digital Signature Scheme 42413.3Schnorr Digital Signature Scheme 42513.4NIST Digital Signature Algorithm 42613.5Elliptic Curve Digital Signature Algorithm 43013.6RSA-PSS Digital Signature Algorithm 43313.7Key Terms, Review Questions, and Problems 438PART FIVE: MUTUAL TRUST 441Chapter 14 Key Management and Distribution 44114.1Symmetric Key Distribution Using Symmetric Encryption 44214.2Symmetric Key Distribution Using Asymmetric Encryption 451Distribution of Public Keys 45414.314.4X.509 Certificates 4595

6CONTENTS14.5Public-Key Infrastructure 46714.6Key Terms, Review Questions, and Problems 469Chapter 15 User Authentication 47315.1Remote User-Authentication Principles 47415.2Remote User-Authentication Using Symmetric Encryption 47815.3Kerberos 48215.4Remote User-Authentication Using Asymmetric Encryption 50015.5Federated Identity Management 50215.6Personal Identity Verification 50815.7Key Terms, Review Questions, and Problems 515PART SIX: NETWORK AND INTERNET SECURITY 519Chapter 16 Network Access Control and Cloud Security 51916.1Network Access Control 52016.2Extensible Authentication Protocol 52316.3IEEE 802.1X Port-Based Network Access Control 52716.4Cloud Computing 52916.5Cloud Security Risks and Countermeasures 53516.6Data Protection in the Cloud 53716.7Cloud Security as a Service 54116.8Addressing Cloud Computing Security Concerns 54416.9Key Terms, Review Questions, and Problems 545Chapter 17 Transport-Level Security 54617.1Web Security Considerations 54717.2Transport Layer Security 54917.3HTTPS 56617.4Secure Shell (SSH) 56717.5Key Terms, Review Questions, and Problems 579Chapter 18 Wireless Network Security 58118.1Wireless Security 58218.2Mobile Device Security 58518.3IEEE 802.11 Wireless LAN Overview 58918.4IEEE 802.11i Wireless LAN Security 59518.5Key Terms, Review Questions, and Problems 610Chapter 19 Electronic Mail Security 61219.1Internet Mail Architecture 61319.2Email Formats 61719.3Email Threats and Comprehensive Email Security 62519.4S/MIME 62719.5Pretty Good Privacy 63819.6DNSSEC 63919.7DNS-Based Authentication of Named Entities 64319.8Sender Policy Framework 64519.9DomainKeys Identified Mail 648

CONTENTS19.1019.11Chapter 2020.120.220.320.420.520.620.7Domain-Based Message Authentication, Reporting, and Conformance 654Key Terms, Review Questions, and Problems 659IP Security 661IP Security Overview 662IP Security Policy 668Encapsulating Security Payload 673Combining Security Associations 681Internet Key Exchange 684Cryptographic Suites 692Key Terms, Review Questions, and Problems 694APPENDICES 696Appendix A Projects for Teaching Cryptography and Network Security 696A.1Sage Computer Algebra Projects 697A.2Hacking Project 698A.3Block Cipher Projects 699A.4Laboratory Exercises 699A.5Research Projects 699A.6Programming Projects 700A.7Practical Security Assessments 700A.8Firewall Projects 701A.9Case Studies 701A.10Writing Assignments 701A.11Reading/Report Assignments 702A.12Discussion Topics 702Appendix B Sage Examples edits 753Index 754Linear Algebra and Matrix Functionality 704Chapter 2: Number Theory 705Chapter 3: Classical Encryption 710Chapter 4: Block Ciphers and the Data Encryption Standard 713Chapter 5: Basic Concepts in Number Theory and Finite Fields 717Chapter 6: Advanced Encryption Standard 724Chapter 8: Pseudorandom Number Generation and Stream Ciphers 729Chapter 9: Public-Key Cryptography and RSA 731Chapter 10: Other Public-Key Cryptosystems 734Chapter 11: Cryptographic Hash Functions 739Chapter 13: Digital Signatures 7417447

8CONTENTSONLINE CHAPTERS AND APPENDICES1PART SEVEN: SYSTEM SECURITYChapter 21 Malicious Software21.1Types of Malicious Software (Malware)21.2Advanced Persistent Threat21.3Propagation—Infected Content—Viruses21.4Propagation—Vulnerability Exploit—Worms21.5Propagation—Social Engineering—Spam E-mail, Trojans21.6Payload—System Corruption21.7Payload—Attack Agent—Zombie, Bots21.8Payload—Information Theft—Keyloggers, Phishing, Spyware21.9Payload—Stealthing—Backdoors, Rootkits21.10Countermeasures21.11Distributed Denial of Service Attacks21.12References21.13Key Terms, Review Questions, and ProblemsChapter 22 Intruders22.1Intruders22.2Intrusion Detection22.3Password Management22.4References22.5Key Terms, Review Questions, and ProblemsChapter 23 Firewalls23.1The Need for Firewalls23.2Firewall Characteristics and Access Policy23.3Types of Firewalls23.4Firewall Basing23.5Firewall Location and Configurations23.6References23.7Key Terms, Review Questions, and ProblemsPART EIGHT: LEGAL AND ETHICAL ISSUESChapter 24 Legal and Ethical Aspects24.1Cybercrime and Computer Crime24.2Intellectual Property24.3Privacy24.4Ethical Issues24.5Recommended Reading24.6References24.7Key Terms, Review Questions, and Problems24.AInformation Privacy1Online chapters, appendices, and other documents are at the Companion Website, available via theaccess card at the front of this book.

CONTENTSAppendix CSage ExercisesAppendix DStandards and Standard-Setting OrganizationsAppendix EBasic Concepts from Linear AlgebraAppendix FMeasures of Secrecy and SecurityAppendix GSimplified DESAppendix HEvaluation Criteria for AESAppendix ISimplified AESAppendix JThe Knapsack AlgorithmAppendix KProof of the Digital Signature AlgorithmAppendix LTCP/IP and OSIAppendix MJava Cryptographic APIsAppendix NMD5 Hash FunctionAppendix OData Compression Using ZIPAppendix PPGPAppendix QThe International Reference AlphabetAppendix RProof of the RSA AlgorithmAppendix SData Encryption StandardAppendix TKerberos Encryption TechniquesAppendix UMathematical Basis of the Birthday AttackAppendix VEvaluation Criteria for SHA-3Appendix WThe Complexity of AlgorithmsAppendix XRadix-64 ConversionAppendix YThe Base Rate FallacyGlossary9

NOTATIONSymbolExpressionMeaningD, KD(K, Y)Symmetric decryption of ciphertext Y using secret key KD, PRaD(PRa, Y)Asymmetric decryption of ciphertext Y using A’s private key PRaD, PUaD(PUa, Y)Asymmetric decryption of ciphertext Y using A’s public key PUaE, KE(K, X)Symmetric encryption of plaintext X using secret key KE, PRaE(PRa, X)Asymmetric encryption of plaintext X using A’s private key PRaE, PUaE(PUa, X)Asymmetric encryption of plaintext X using A’s public key PUaKSecret keyPRaPrivate key of user APUaPublic key of user AMAC, KMAC(K, X)Message authentication code of message X using secret key KGF(p)The finite field of order p, where p is prime.The field is defined asthe set Zp together with the arithmetic operations modulo p.GF(2n)The finite field of order 2nZnSet of nonnegative integers less than ngcdgcd(i, j)Greatest common divisor; the largest positive integer thatdivides both i and j with no remainder on division.moda mod mRemainder after division of a by mmod, Ka K b (mod m)a mod m b mod mmod, [a [ b (mod m)a mod m b mod mdlogdlog a,p(b)Discrete logarithm of the number b for the base a (mod p)wf(n)The number of positive integers less than n and relativelyprime to n.This is Euler’s totient function.ΣΠna aia1 a2 g ani 1nq aia1 * a2 * g * ani 1 i ji divides j, which means that there is no remainder when j isdivided by i , a Absolute value of a10Hiva-Network.Com

NOTATIONSymbolExpressionMeaning}x}yx concatenated with y x yx is approximately equal to y x yExclusive-OR of x and y for single-bit variables;Bitwise exclusive-OR of x and y for multiple-bit variables:, ;:x ;The largest integer less than or equal to x x SThe element x is contained in the set S.·A · (a1, a2,c ak)The integer A corresponds to the sequence of integers(a1, a2, c ak)11

PREFACEWHAT’S NEW IN THE SEVENTH EDITIONIn the four years since the sixth edition of this book was published, the field has seen continued innovations and improvements. In this new edition, I try to capture these changes whilemaintaining a broad and comprehensive coverage of the entire field. To begin this process ofrevision, the sixth edition of this book was extensively reviewed by a number of professorswho teach the subject and by professionals working in the field. The result is that, in manyplaces, the narrative has been clarified and tightened, and illustrations have been improved.Beyond these refinements to improve pedagogy and user-friendliness, there have beensubstantive changes throughout the book. Roughly the same chapter organization has beenretained, but much of the material has been revised and new material has been added. Themost noteworthy changes are as follows: Fundamental security design principles: Chapter 1 includes a new section discussing thesecurity design principles listed as fundamental by the National Centers of AcademicExcellence in Information Assurance/Cyber Defense, which is jointly sponsored by theU.S. National Security Agency and the U.S. Department of Homeland Security. Attack surfaces and attack trees: Chapter 1 includes a new section describing these twoconcepts, which are useful in evaluating and classifying security threats.Number theory coverage: The material on number theory has been consolidatedinto a single chapter, Chapter 2. This makes for a convenient reference. The relevantportions of Chapter 2 can be assigned as needed.Finite fields: The chapter on finite fields has been revised and expanded with additional text and new figures to enhance understanding.Format-preserving encryption: This relatively new mode of encryption is enjoyingincreasing commercial success. A new section in Chapter 7 covers this method.Conditioning and health testing for true random number generators: Chapter 8 nowprovides coverage of these important topics.User authentication model: Chapter 15 includes a new description of a general modelfor user authentication, which helps to unify the discussion of the various approachesto user authentication.Cloud security: The material on cloud security in Chapter 16 has been updated andexpanded to reflect its importance and recent developments.Transport Layer Security (TLS): The treatment of TLS in Chapter 17 has been updated,reorganized to improve clarity, and now includes a discussion of the new TLS version 1.3.Email Security: Chapter 19 has been completely rewritten to provide a comprehensiveand up-to-date discussion of email security. It includes:— New: discussion of email threats and a comprehensive approach to email security.— New: discussion of STARTTLS, which provides confidentiality and authenticationfor SMTP. 12

PREFACE13— Revised: treatment of S/MIME has been updated to reflect the latest version 3.2.— New: discussion of DNSSEC and its role in supporting email security.— New: discussion of DNS-based Authentication of Named Entities (DANE) and theuse of this approach to enhance security for certificate use in SMTP and S/MIME.— New: discussion of Sender Policy Framework (SPF), which is the standardized wayfor a sending domain to identify and assert the mail senders for a given domain.— Revised: discussion of DomainKeys Identified Mail (DKIM) has been revised.— New: discussion of Domain-based Message Authentication, Reporting, and Conformance (DMARC) allows email senders to specify policy on how their mail shouldbe handled, the types of reports that receivers can send back, and the frequencythose reports should be sent.OBJECTIVESIt is the purpose of this book to provide a practical survey of both the principles and practiceof cryptography and network security. In the first part of the book, the basic issues to beaddressed by a network security capability are explored by providing a tutorial and surveyof cryptography and network security technology. The latter part of the book deals with thepractice of network security: practical applications that have been implemented and are inuse to provide network security.The subject, and therefore this book, draws on a variety of disciplines. In particular,it is impossible to appreciate the significance of some of the techniques discussed in thisbook without a basic understanding of number theory and some results from probabilitytheory. Nevertheless, an attempt has been made to make the book self-contained. The booknot only presents the basic mathematical results that are needed but provides the readerwith an intuitive understanding of those results. Such background material is introducedas needed. This approach helps to motivate the material that is introduced, and the authorconsiders this preferable to simply presenting all of the mathematical material in a lump atthe beginning of the book.SUPPORT OF ACM/IEEE COMPUTER SCIENCE CURRICULA 2013The book is intended for both academic and professional audiences. As a textbook, it isintended as a one-semester undergraduate course in cryptography and network security forcomputer science, computer engineering, and electrical engineering majors. The changes tothis edition are intended to provide support of the ACM/IEEE Computer Science Curricula2013 (CS2013). CS2013 adds Information Assurance and Security (IAS) to the curriculum recommendation as one of the Knowledge Areas in the Computer Science Body of Knowledge.The document states that IAS is now part of the curriculum recommendation because of thecritical role of IAS in computer science education. CS2013 divides all course work into threecategories: Core-Tier 1 (all topics should be included in the curriculum), Core-Tier-2 (all oralmost all topics should be included), and elective (desirable to provide breadth and depth).In the IAS area, CS2013 recommends topics in Fundamental Concepts and Network Security

14PREFACEin Tier 1 and Tier 2, and Cryptography topics as elective. This text covers virtually all of thetopics listed by CS2013 in these three categories.The book also serves as a basic reference volume and is suitable for self-study.PLAN OF THE TEXTThe book is divided into eight parts. BackgroundSymmetric CiphersAsymmetric CiphersCryptographic Data Integrity AlgorithmsMutual TrustNetwork and Internet SecuritySystem SecurityLegal and Ethical IssuesThe book includes a number of pedagogic features, including the use of the computeralgebra system Sage and numerous figures and tables to clarify the discussions. Each chapter includes a list of key words, review questions, homework problems, and suggestionsfor further reading. The book also includes an extensive glossary, a list of frequently usedacronyms, and a bibliography. In addition, a test bank is available to instructors.INSTRUCTOR SUPPORT MATERIALSThe major goal of this text is to make it as effective a teaching tool for this exciting andfast-moving subject as possible. This goal is reflected both in the structure of the book and inthe supporting material. The text is accompanied by the following supplementary materialthat will aid the instructor: Solutions manual: Solutions to all end-of-chapter Review Questions and Problems. Projects manual: Suggested project assignments for all of the project categories listedbelow.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 with a separate file of answers. Sample syllabuses: The text contains more material than can be conveniently coveredin one semester. Accordingly, instructors are provided with several sample syllabusesthat guide the use of the text within limited time.All of these support materials are available at the Instructor Resource Center(IRC) for this textbook, which can be reached through the publisher’s Web sitewww.pearsonglobaleditions.com/stallings. To gain access to the IRC, please contact yourlocal Pearson sales representative.

PREFACE15PROJECTS AND OTHER STUDENT EXERCISESFor many instructors, an important component of a cryptography or network security courseis a project or set of projects by which the student gets hands-on experience to reinforceconcepts from the text. This book provides an unparalleled degree of support, including aprojects component in the course. The IRC not only includes guidance on how to assign andstructure the projects, but also includes a set of project assignments that covers a broad rangeof topics from the text: Sage projects: Described in the next section. Hacking project: Exercise designed to illuminate the key issues in intrusion detectionand prevention.Block cipher projects: A lab that explores the operation of the AES encryption algorithm by tracing its execution, computing one round by hand, and then exploring thevarious block cipher modes of use. The lab also covers DES. In both cases, an onlineJava applet is used (or can be downloaded) to execute AES or DES.Lab exercises: A series of projects that involve programming and experimenting withconcepts from the book.Research projects: A series of research assignments that instruct the student to researcha particular topic on the Internet and write a report.Programming projects: A series of programming projects that cover a broad range oftopics and that can be implemented in any suitable language on any platform.Practical security assessments: A set of exercises to examine current infrastructure andpractices of an existing organization.Firewall projects: A portable network firewall visualization simulator, together withexercises for teaching the fundamentals of firewalls.Case studies: A set of real-world case studies, including learning objectives, casedescription, and a series of case discussion questions.Writing assignments: A set of suggested writing assignments, organized by chapter.Reading/report assignments: A list of papers in the literature—one for each chapter—that can be assigned for the student to read and then write a short report. This diverse set of projects and other student exercises enables the instructor to usethe book as one component in a rich and varied learning experience and to tailor a courseplan to meet the specific needs of the instructor and students. See Appendix A in this bookfor details.THE SAGE COMPUTER ALGEBRA SYSTEMOne of the most important features of this book is the use of Sage for cryptographic examplesand homework assignments. Sage is an open-source, multiplatform, freeware package thatimplements a very powerful, flexible, and easily learned mathematics and computer algebrasystem. Unlike competing systems (such as Mathematica, Maple, and MATLAB), there are

PREFACE 17Homework problems and solutions: To aid the student in understanding the material,a separate set of homework problems with solutions are available.Key papers: A number of 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 textand provided online.Sage code: The Sage code from the examples in Appendix B is useful in case the studentwants to play around with the examples.To access the Companion Website, follow the instructions for “digital resources forstudents” found in the front of this book.ACKNOWLEDGMENTSThis new edition has benefited from review by a number of people who gave generouslyof their time and expertise. The following professors reviewed all or a large part of themanuscript: Hossein Beyzavi (Marymount University), Donald F. Costello (University ofNebraska–Lincoln), James Haralambides (Barry University), Anand Seetharam (CaliforniaState University at Monterey Bay), Marius C. Silaghi (Florida Institute of Technology),Shambhu Upadhyaya (University at Buffalo), Zhengping Wu (California State Universityat San Bernardino), Liangliang Xiao (Frostburg State University), Seong-Moo (Sam) Yoo(The University of Alabama in Huntsville), and Hong Zhang (Armstrong State University).Thanks also to the people who provided detailed technical reviews of one or morechapters: Dino M. Amaral, Chris Andrew, Prof. (Dr). C. Annamalai, Andrew Bain, RiccardoBernardini, Olivier Blazy, Zervopoulou Christina, Maria Christofi, Dhananjoy Dey, MarioEmmanuel, Mike Fikuart, Alexander Fries, Pierpaolo Giacomin, Pedro R. M. Inácio,Daniela Tamy Iwassa, Krzysztof Janowski, Sergey Katsev, Adnan Kilic, Rob Knox, MinaPourdashty, Yuri Poeluev, Pritesh Prajapati, Venkatesh Ramamoorthy, Andrea Razzini,Rami Rosen, Javier Scodelaro, Jamshid Shokrollahi, Oscar So, and David Tillemans.In addition, I was fortunate to have reviews of individual topics by “subject-areagurus,” including Jesse Walker of Intel (

3 CONTENTS Notation 10 Preface 12 About the Author 18 PART ONE: BACKGROUND 19 Chapter 1 Computer and Network Security Concepts 19 1.1 Computer Security Concepts 21 1.2 The OSI Security Architecture 26 1.3 Security Attacks 27 1.4 Security Services 29 1.5 Security Mechanisms 32 1.6 Fundamental Security Design Principles 34 1.7 Attack Surfaces and Attack Trees 37

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