An-Overview-Cryptography

An-Overview-Cryptography - 9/1/2010 An Overview of...

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An Overview of Cryptography Gary C. Kessler 30 June 2010 (Original version: May 1998) A much shorter, edited version of this paper appears in the 1999 Edition of Handbook on Local Area Networks , published by Auerbach in September 1998. Since that time, this article has taken on a life of its own. .. CONTENTS 1. INTRODUCTION 2. THE PURPOSE OF CRYPTOGRAPHY 3. TYPES OF CRYPTOGRAPHIC ALGORITHMS 3.1. Secret Key Cryptography 3.2. Public-Key Cryptography 3.3. Hash Functions 3.4. Why Three Encryption Techniques? 3.5. The Significance of Key Length 4. TRUST MODELS 4.1. PGP Web of Trust 4.2. Kerberos 4.3. Public Key Certificates and Certification Authorities 4.4. Summary 5. CRYPTOGRAPHIC ALGORITHMS IN ACTION 5.1. Password Protection 5.2. Some of the Finer Details of Diffie-Hellman Key Exchange 5.3. Some of the Finer Details of RSA Public-Key Cryptography 5.4. Some of the Finer Details of DES, Breaking DES, and DES Variants 5.5. Pretty Good Privacy (PGP) 5.6. IP Security (IPsec) Protocol 5.7. The SSL "Family" of Secure Transaction Protocols for the World Wide Web 5.8. Elliptic Curve Cryptography 5.9. The Advanced Encryption Standard and Rijndael 5.10. Cisco's Stream Cipher 6. CONCLUSION. .. OF SORTS 7. REFERENCES AND FURTHER READING A. SOME MATH NOTES A.1. The Exclusive-OR (XOR) Function A.2. The modulo Function ABOUT THE AUTHOR FIGURES 1. Three types of cryptography: secret-key, public key, and hash function. 2. Sample application of the three cryptographic techniques for secure communication. 3. Kerberos architecture. 4. GTE Cybertrust Global Root- issued certificate (Netscape Navigator). 5. Sample entries in Unix/Linux password files. 6. DES enciphering algorithm. 7. A PGP signed message. 8. A PGP encrypted message. 9. The decrypted message. 10. IPsec Authentication Header format. 11. IPsec Encapsulating Security Payload format. 12. IPsec tunnel and transport modes for AH. 13. IPsec tunnel and transport modes for ESP. 14. SSL v3 configuration screen (Netscape Navigator). 15. SSL/TLS protocol handshake. 16. Elliptic curve addition. 17. AES pseudocode. TABLES 1. Minimum Key Lengths for Symmetric Ciphers. 2. Contents of an X.509 V3 Certificate. 3. Other Crypto Algorithms and Systems of Note. 4. ECC and RSA Key Comparison. 9/1/2010 An Overview of Cryptography www.garykessler.net/library/crypto.html 1/63
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1. INTRODUCTION Does increased security provide comfort to paranoid people? Or does security provide some very basic protections that we are naive to believe that we don't need? During this time when the Internet provides essential communication between tens of millions of people and is being increasingly used as a tool for commerce, security becomes a tremendously important issue to deal with. There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting passwords. One essential aspect for secure communications is that of cryptography, which is the focus of this chapter. But it is important to note that while cryptography is necessary for secure communications, it is not by itself sufficient . The reader is advised, then, that the topics covered in this
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An-Overview-Cryptography - 9/1/2010 An Overview of...

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