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Cryptography Decrypted

Cryptography Decrypted

H. Mel, Doris Baker

Jan 2001, Paperback, 384 pages
ISBN13: 9780201616477
ISBN10: 0201616475
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Cryptography is at the heart of computer security: without it, secure e-commerce and Internet communications would be impossible. Decision-makers and sophisticated computer users need to understand cryptography -- but most explanations are highly mathematical and technical. Cryptography Decrypted explains cryptography in "plain English" -- and is authoritative and thorough enough to address the needs of professionals. It explains the processes step-by-step, with extensive visuals. The authors present the elements of cryptography systems; public key infrastructure (PKI); and the IPSec standard for virtual private network security; then review real-world systems and their applications. They show how real-world systems are attacked, and how to protect them; introduce essential cryptographic terms; and present the fascinating history of cryptography through sidebars highlighting its important events, people, and breakthroughs. For every decision-maker and computer user who needs to understand cryptography, this book is also ideal for security pros who need to educate management about cryptography.

Fundamental security concepts like cryptography and digital signatures are becoming as much a part of our everyday lives as megabytes and the Internet. Anyone working with computer security--security professionals, network administrators, IT managers, CEOs, and CIOs--need to have a comfortable understanding of the cryptographic concepts in this book.

Cryptography Decrypted shows you how to safeguard digital possessions. It is a clear, comprehensible, and practical guide to the essentials of computer cryptography, from Caesar's Cipher through modern-day public key. Cryptographic capabilities like detecting imposters and stopping eavesdropping are thoroughly illustrated with easy-to-understand analogies, visuals, and historical sidebars.

You need little or no background in cryptography to read Cryptography Decrypted. Nor does it require technical or mathematical expertise. But for those with some understanding of the subject, this book is comprehensive enough to solidify knowledge of computer cryptography and challenge those who wish to explore the high-level math appendix.

Divided into four parts, the book explains secret keys and secret key methods like DES, public and private keys, and public key methods like RSA; how keys are distributed through digital certificates; and three real-world systems. Numerous graphics illustrate and clarify common cryptographic terminology throughout.

You will find coverage of such specific topics as:
  • Secret key and secret key exchanges
  • Public and private keys
  • Digital signatures
  • Digital certificates, Public Key Infrastructure (PKI), and PGP
  • Hashes and message digests
  • Secure e-mail, secure socket layer (SSL), and Internet Protocol Security (IPsec)
  • Protecting keys
  • Cryptographic attacks
  • Authentication, confidentiality, integrity, and nonrepudiation

"Even after ten years working in the field of information protection for a major electronics manufacturing company, I learned a lot from this book. I think you will too."

--From the Foreword by John Kinyon






1. Locks and Keys.
Locks and Combinations.Defining Cryptographic Terms.Making and Solving Puzzles.Review.2. Substitution and Caesar's Cipher.
Cryptanalysis of Caesar's Cipher.Empowering the Masses.The Importance of Separating the Method and the Key.Adding Keys.A Weakness of Caesar's Ciphers: The Failure to Hide Linguistic Patterns.More Complex Substitution: Vigenere's Cipher.Review.3. Transposition Ciphers: Moving Around.
Patterns and Cryptanalysis.Adding Complexity.Computer Transposition.Combining Substitution and Transposition.Review.4. Diffuse and Confuse: How Cryptographers Win the End Game.
Diffusion.The Polybius Cipher.The Principle of Confusion.Cryptographic Locks and Keys.Review.5. DES Isn't Strong Anymore.
The Historical Need for an Encryption Standard.Cycling Through Computer Keys.Double and Triple DES.DES (and Other Block Cipher) Modes.The Avalanche Effect.Supplement: Binary Numbers and Computer Letters.Review.6. Evolution of Cryptography: Going Global.
Early Cryptography.Commercial and Military Needs.Entering the Computer Age.Review.7. Secret Key Assurances.
Confidentiality.Authentication.An Authentication Attack.Not Really Random Numbers.Integrity.Using the MAC for Message Integrity Assurance.Why Bother Using a Message Authentication Code?File and MAC Compression.Nonrepudiation: Secret Keys Can't Do It.Review.8. Problems with Secret Key Exchange.
The Problem and the Traditional Solution.Using a Trusted Third Party.Key Distribution Center and Key Recovery.Problems with Using a Trusted Third Party.Growth in the Number of Secret Keys.Trust and Lifetime.Review.


9. Pioneering Public Key: Public Exchange of Secret Keys.
The Search for an Innovative Key Delivery Solution.Developing an Innovative Secret Key Delivery Solution.First Attempt: A Database of Key/Serial Number Pairs.Second Attempt: An Encrypted Database of Key/Serial Number Pairs.Merkle's Insight: Individually Encrypted Key/Serial Number Pairs.Black Hat's Frustrating Problem.The Key to Public Key Technology.A New Solution: Diffie-Hellman-Merkle Key Agreement.Alice and Bob Openly Agree on a Secret Key.Problems with the Diffie-Hellman Method.Separate Encryption and Decryption Keys.Review.10. Confidentiality Using Public Keys.
New Twists on Old Security Issues.Confidentiality Assurances.Distribution of Public Keys.Two-Way Confidentiality.Review.11. Making Public Keys: Math Tricks.
Alice's Easy Problem.Grade School Math Tricks.More Grade School Math.Division and Remainders: Modular Math.Modular Inverses.Using Modular Inverses to Make a Public Key.Putting It All Together.Giving BlackHat a Difficult, Time-Consuming Problem.Trapdoor to the Easy Problem.Knapsack Cryptography.Modulo Calculations.Exercise: Find Which Numbers Sum to 103.Review.12. Creating Digital Signatures Using the Private Key.
Written and Digital Signature Assurances.Reviewing and Comparing Authentication.Secret Key Authentication.Private Key Authentication 117Authentication and Integrity Using Private and Secret Keys.Private Key Authentication Methods.RSA.DSA.Signing Terminology.Nonrepudiation.Assurances in Both Directions.Summary of Public Key Assurances.Public Key Means Public / Private Key.Assurance Initiated.Compressing before Signing.Review.13. Hashes: Non-keyed Message Digests.
Detecting Unintentional Modifications.Detecting Intentional Modifications.Signing the Message Digest.Detecting BlackHat's Forgery.Replay Attacks.Supplement: Unsuccessfully Imitating a Message Digest.Review.14. Message Digest Assurances.
Two Message Digest Flavors.Non-keyed Message Digest Assurances.One-wayness.Collision Resistance.Weak Collision Resistance.Examples of One-way and Weak Collision Resistance.Strong Collision Resistance.Non-keyed Digest Implementations.Keyed Message Digest Assurances.A MAC Made with DES.DES-MAC Security.Message Digest Compression.Digest Speed Comparisons.Hashed MAC.Review.15. Comparing Secret Key, Public Key, and Message Digests.
Encryption Speed.Key Length.Ease of Key Distribution.Cryptographic Assurances.Symmetric (Secret) Key.Asymmetric (Public) Key.Review.


16. Digital Certificates.
Verifying a Digital Certificate.Attacking Digital Certificates.Attacking the Creator of the Digital Certificate.Malicious Certificate Creator.Attacking the Digital Certificate User.The Most Devastating Attack.Understanding Digital Certificates: A Familiar Comparison.Issuer and Subject.Issuer Authentication.Transfer of Trust from the Issuer to the Subject.Issuer's Limited Liability.Time Limits.Revoking Trust.More than One Certificate.Fees for Use.The Needs of Digital Certificate Users.Getting Your First Public Key.Certificates Included in Your Browser.Review.17. X.509 Public Key Infrastructure.
Why Use X.509 Certificate Management?What Is a Certificate Authority?Application, Certification, and Issuance.Certificate Revocation.Polling and Pushing: Two CRL Delivery Models.Building X.509 Trust Networks.Root Certificates.More Risks and Precautions.Distinguished Names.Certification Practice Statement.X.509 Certificate Data.Challenge Response Protocol.Review.18. Pretty Good Privacy and the Web of Trust.
The History of PGP.Comparing X.509 and PGP Certificates.Building Trust Networks.Bob Validates Alice's Key.Casey Validates Alice's Key Sent by Bob.Dawn Validates Alice's Key Sent by Casey via Bob.Web of Trust.PGP Certificate Repositories and Revocation.Compatibility of X.509 and PGPReview.


E-mail Cryptographic Parameters.Negotiation of SSL and IPsec Cryptographic Parameters.User Initiation of Cryptographic E-mail, SSL, and Ipsec.19. Secure E-mail.
Generic Cryptographic E-mail Messages.Invoking Cryptographic Services.Confidentiality and Authentication.Choosing Services.Positioning Services.Deterring E-mail Viruses.Review.20. Secure Socket Layer and Transport.
Layer Security.History of SSL.Overview of an SSL Session.An SSL Session in Detail.Hello and Negotiate Parameters.Key Agreement (Exchange).Authentication.Confidentiality and Integrity.TLS Variations.Anonymous Diffie-Hellman.Fixed and Ephemeral Diffie-Hellman.Comparing TLS, SSL v3, and SSL v2.A Big Problem with SSL v2.A Possible Problem with TLS and SSL.Generating Shared Secrets.Bob Authenticates Himself to AliceDotComStocks.Review.21. IPsec Overview.
Enhanced Security.Key Management.Manual Distribution.Automated Distribution.IPsec Part 1: User Authentication and Key Exchange Using IKE.SSL/TLS and IPsec Key Agreement.Security Association.Phases.IKE Nomenclature.Benefits of Two-Phase Key Exchange.IPsec Part 2: Bulk Data Confidentiality and Integrity for Message or File Transport.Protocol and Mode.ESP Examples.AH Examples.Management Control.Implementation Incompatibilities and Complications.Review.22. Cryptographic Gotchas.
Replay Attack.Man-in-the-Middle Attack.Finding Your Keys in Memory.Does Confidentiality Imply Integrity?Example 1.Example 2: Cut-and-Paste Attack.Public Key as a Cryptanalysis Tool.Example 1: The Chosen Plaintext Attack.Public Key Cryptographic Standards.Example 2: The Bleichenbacher Attack.BlackHat Uses Bob's RSA Private Key.Review.23. Protecting Your Keys.
Smart Cards.Types of Smart Cards.What's Inside a Smart Card.Protections and Limitations.Smart Card Attacks.Review.Epilogue.
Appendix A. Public Key Mathematics (and Some Words on Random Numbers).
Appendix B. (A Few) IPsec Details.
Index. 0201616475T04062001

H.X. Mel consults and develops computer systems for organizations such as Lucent, Xerox, MIT, the U.S. Government, Motorola, Goldman Sachs, and PricewaterhouseCoopers. Doris Baker is a freelance technical writer and editor.