Chapter 6 Cryptography CISSP Study Guide BIS 4113/6113

Goals of Cryptography Confidentiality Integrity Authentication Nonrepudiation Prevents masquerading as the sender AES Example

Historical Uses of Cryptography Caesar Cipher Civil War

World War II Program Ultra Enigma Machine “Windtalkers”

Basic Terminology “Security through obscurity” Plain Text Cipher Text Encryption Decryption Kerchoff’s Principle Alogrithm public, keys kept private Codes vs. Ciphers Data at Rest / Data in Motion

Encyrption Algorithms Symmetric Key “Shared secret” Shortcomings Key distribution Key regeneration every time user leaves group Internet Encryption Decryption P C C P Secret Key Secret Key

Examples AES example Banking transactions Many VPN connections One half of SSL (p.220)

Encyrption Algorithms Asymmetric Key Same key pair used for all users Private key cannot be derived from public key Shortcomings Slow speed of operation Internet Encryption Decryption P C C P Receiver’s Public Key Receiver’s Private Key

Other Comparisons (p.386) Symmetric Asymmetric Encryption Requirements Single Shared Key (2 Privates) Key Pair Sets (Public & Private) Key Exchange “Out of Band” “In Band” Adding Additional Users Not Scalable Scalable Operation Fast Slow Amount of Data Bulk Encryption Small Blocks Goals Achieved (Better?) Confidentiality Integrity Authenticity Nonrepudiation

Private Key Management Key Transfer Offline distribution Public key transfer of private keys Key Storage Secondary storage Non-volatile RAM Key Use Periodic rotation Crytographic Life Cycle

Assignment #4 Generating Asymmetric Key Pairs Send me your public key