Table of Contents
Introduction to Practical Issues in Cryptography
Overview
The history of cryptography*
A classification scheme for ciphers* Gary Knight  Cryptanalysts Corner, Cryptologia 1 (January 1978):6874.
Ancient cryptosystems
More Ancient Cryptography
More Ancient Cryptography
More History
More Cryptography
Other Codes
Effectiveness over time
Techniques for breaking most of the ancient ciphers
Information theory and cryptography*
Shannon's papers
Shannon48
Some comments on Shannon48
Fundamentals of information theoretic cryptography
Unicity Distance for English
Special Cases
Pseudorandom != Random
The Concept of Workload
Things to increase workload
Shannon’s Model of Cryptography
A Spatial Model of Cryptosystems
Attacks on Cryptosystems
More Attacks on Cryptosystems
Still more attacks on cryptosystems?
Cryptosystem Subtypes
Methods used to break WWII cryptosystems.
Many ciphers, common flaws
Human Flaws in WWII
Human Flaws in WWII
Technical breakthroughs in WWII
Other aspects of theory
Nkey systems
An nkey cryptosystem
Some interesting questions*
More questions*
How much does the attacker learn from watching the system operate?
If the attacker guesses some things, and if they are right, how does that affect the result?
What can an attacker reasonably guess?
Does keeping Te and Td secret increase workload and to what extent?
Can we count on secret transforms? When?
Can we use Ke or Kd forever? How long then? How do we determine it?
Can you trust cryptography to keep secrets for a long time? How long? Why?
Can cryptography be used to assure integrity?
Can cryptography be used to assure identity?
Implementation*
The key distribution problem
The key maintenance problem
The cryptographic protocol problem
The key scheduling problem
The key generation/selection problem
Passwords are cryptobased
Passwords
Modern cryptosystem types and functions*
DES
3DES
IDEA
RSA
MD5
Others
Handson cryptography today*
Install and learn to operate modern systems
Use of cryptosystems daytoday
More systems in use
Infrastructure Encryption
Embedded encryption
Attacking modern cryptosystems
Rule 0: The people are weak links
Rule 1: Attack live systems
Rule 2: They have a way to use it
Rule 3: Exhaustive search fails
Rule 4: Cryptanalysis is expensive
Rule 5: OSs are weaker than cryptosystems
Rule 6: Protocols are weaker than transforms
50 Ways
Stegonography today*
Classic Steganography
Steganographic classics
Making Digital Steganography
Detecting digital steganography
Breaking steganography
Combining steganography and cryptography
Thank You
