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. The student needs 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.
I. SECRET KEY CRYPTOGRAPHY.1. Locks and Keys.
Defining Cryptographic Terms.
Making and Solving Puzzles.
2. Substitution and Caesar's Cipher.
Empowering the Masses.
The Importance of Separating the Method and the Key.
More Complex Substitution: Vigenere's Cipher.
3. Transposition Ciphers: Moving Around.
Combining Substitution and Transposition.
4. Diffuse and Confuse: How Cryptographers Win the End Game.
The Principle of Confusion.
Cryptographic Locks and Keys.
5. DES Isn't Strong Anymore.
Cycling Through Computer Keys.
Double and Triple DES.
DES (and Other Block Cipher) Modes.
The Avalanche Effect.
Supplement: Binary Numbers and Computer Letters.
6. Evolution of Cryptography: Going Global.
Commercial and Military Needs.
Entering the Computer Age.
7. Secret Key Assurances.
Not Really Random Numbers.
Why Bother Using a Message Authentication Code?
File and MAC Compression.
Nonrepudiation: Secret Keys Can't Do It.
8. Problems with Secret Key Exchange.
Using a Trusted Third Party.
Key Distribution Center and Key Recovery.
Problems with Using a Trusted Third Party.
Trust and Lifetime.
II. PUBLIC KEY CRYPTOGRAPHY.
9. Pioneering Public Key: Public Exchange of Secret Keys.
Developing an Innovative Secret Key Delivery Solution.
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.
Problems with the Diffie-Hellman Method.
Separate Encryption and Decryption Keys.
10. Confidentiality Using Public Keys.
Distribution of Public Keys.
11. Making Public Keys: Math Tricks.
Grade School Math Tricks.
More Grade School Math.
Division and Remainders: Modular Math.
Using Modular Inverses to Make a Public Key.
Putting It All Together.
Trapdoor to the Easy Problem.
Exercise: Find Which Numbers Sum to 103.
12. Creating Digital Signatures Using the Private Key.
Reviewing and Comparing Authentication.
Private Key Authentication 117
Authentication and Integrity Using Private and Secret Keys.
Private Key Authentication Methods.
Assurances in Both Directions.
Summary of Public Key Assurances.
Compressing before Signing.
13. Hashes: Non-keyed Message Digests.
Detecting Intentional Modifications.
Signing the Message Digest.
Supplement: Unsuccessfully Imitating a Message Digest.
14. Message Digest Assurances.
Non-keyed Message Digest Assurances.
Weak Collision Resistance.
Examples of One-way and Weak Collision Resistance.
Strong Collision Resistance.
Non-keyed Digest Implementations.
Keyed Message Digest Assurances.
Message Digest Compression.
Digest Speed Comparisons.
15. Comparing Secret Key, Public Key, and Message Digests.
Ease of Key Distribution.
Asymmetric (Public) Key.
III. DISTRIBUTION OF PUBLIC KEYS.
16. Digital Certificates.
Attacking Digital Certificates.
Malicious Certificate Creator.
Attacking the Digital Certificate User.
The Most Devastating Attack.
Understanding Digital Certificates: A Familiar Comparison.
Transfer of Trust from the Issuer to the Subject.
Issuer's Limited Liability.
More than One Certificate.
Fees for Use.
The Needs of Digital Certificate Users.
Getting Your First Public Key.
Certificates Included in Your Browser.
17. X.509 Public Key Infrastructure.
What Is a Certificate Authority?
Polling and Pushing: Two CRL Delivery Models.
Building X.509 Trust Networks.
More Risks and Precautions.
Certification Practice Statement.
X.509 Certificate Data.
18. Pretty Good Privacy and the Web of Trust.
Comparing X.509 and PGP Certificates.
Building Trust Networks.
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 PGP
IV. REAL-WORLD SYSTEMS.E-mail Cryptographic Parameters.
Negotiation of SSL and IPsec Cryptographic Parameters.
User Initiation of Cryptographic E-mail, SSL, and Ipsec.
19. Secure E-mail.
Invoking Cryptographic Services.
Confidentiality and Authentication.
Deterring E-mail Viruses.
20. Secure Socket Layer and Transport.
History of SSL.
Overview of an SSL Session.
An SSL Session in Detail.
Key Agreement (Exchange).
Confidentiality and Integrity.
Fixed and Ephemeral Diffie-Hellman.
Comparing TLS, SSL v3, and SSL v2.
A Possible Problem with TLS and SSL.
Generating Shared Secrets.
Bob Authenticates Himself to AliceDotComStocks.
21. IPsec Overview.
IPsec Part 1: User Authentication and Key Exchange Using IKE.
Benefits of Two-Phase Key Exchange.
IPsec Part 2: Bulk Data Confidentiality and Integrity for Message or File Transport.
Implementation Incompatibilities and Complications.
22. Cryptographic Gotchas.
Finding Your Keys in Memory.
Does Confidentiality Imply Integrity?
Example 2: Cut-and-Paste Attack.
Public Key as a Cryptanalysis Tool.
Public Key Cryptographic Standards.
Example 2: The Bleichenbacher Attack.
BlackHat Uses Bob's RSA Private Key.
23. Protecting Your Keys.
What's Inside a Smart Card.
Protections and Limitations.
Smart Card Attacks.
Appendix A. Public Key Mathematics (and Some Words on Random Numbers).
Appendix B. (A Few) IPsec Details.