1. Rotors and Secret-Key Encryption
CS490 - Security in Computing
Copyright © 2005 by Scott Orr and the Trustees of Indiana University

2. Section Overview Enigma Machine Block Cipher Modes
Data Encryption Standard
Triple DES
Rijndael (AES)

3. References Security in Computing, 3rd Ed. Online Resources
Chapter 2 (pgs )
Chapter 10 (pgs )
Online Resources
Why Cryptography Is Harder Than It Looks, Bruce Schneier, CTO - Counterpane Internet Security, Inc.

4. Cipher Disks Developed by Leon Alberti – 1400s Caesar Shifts
Vigenère alphabets
Other users
Confederate Army
Captain Midnight

5. German Enigma Machine Developed by Arthur Scherbius
Goal: Replace pencil and paper ciphers
Components
Keyboard/Lamps
Rotors
Rings
Reflector
Plugboard
Picture Source: Nova

6. Enigma – 1 Rotor a a b b b c c c d d e e f f Source: The Code Book
By Simon Singh

7. Enigma – 2 Rotors a a b b b b c c c d d d e e f f
Source: The Code Book
By Simon Singh

8. Three Rotor Enigma a b c d e f a b c d e f a b c d e f
Source: The Code Book
By Simon Singh

9. Block Ciphers 10101010 11011001 XOR () 1 1 1 1 1 Plaintext Key
Algorithm 1 1 1 1 1
Ciphertext

10. Electronic Code Book (ECB)P1 P2 EK C2 Pn EK Cn
Key EK C1

11. Cipher Block Chaining (CBC)EK C2  Pn EK Cn  IV 
Key EK C1

12. Cipher Feedback Mode (CFB)
Key Pn
Rn-1 EK Rn  Cn

13. Output Feedback Mode (OFB)
Key Pn
Rn-1 EK Rn  Cn

14. Permutations Permutation Permutated Choice Expansion Permutation
Source: Cryptography and Network Security, 2E by William Stallings

15. Data Encryption Standard
Created by IBM called LUCIFER
Adopted in 1977 by National Bureau of Standards (now NIST)
56 bit key to encrypt 64 bit blocks
Consists of 16 stages plus initial/final permutations

16. DES – One Round   Ln – 32 bits Rn – 32 bits Ln+1 – 32 bits
Key
56 bits
E-Box
48 Bits 
Key-Box
48 Bits
S-Box
32 Bits
P-Box 
Ln+1 – 32 bits
Rn+1 – 32 bits
Source: Cryptography and
Network Security, 2E
by William Stallings

17. DES Substitution Boxes
E-Box  Key (48 Bits) S1 S2 S8
P-Box (32 Bits)
Source: Cryptography and
Network Security, 2E
by William Stallings

18. S-Box Lookups 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
101110 S1
1011
Source: Cryptography and
Network Security, 2E
by William Stallings

19. Attacks on DES Weak key size Brute force attacks
Originally used a 128 bit key
Shortened to 56 bits to fit on 1 chip
Brute force attacks
RSA Challenges
Deep Crack – EFF built $210K system
Distributed.Net – 1000s of Internet connected systems working together

20. Triple DES (3DES)
Plaintext
EDES
DDES
KeyD
KeyE
Ciphertext
EDES

21. Rijndael (AES) Structure
Subkey
Subkey
Keyadd
Substitution
Shiftrow
Mixcolumn
Keyadd
Plaintext
Final
Round? No
Yes
Ciphertext
Keyadd
Shiftrow
Substitution
Subkey
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

22. Initial Block Grouping
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

23. Substitution Operation
S-Box
a0,0
a1,0
a2,0
a3,0
a0,1
a1,1
a2,1
a3,1
a0,2
a1,2
a2,2
a3,2
a0,3
a1,3
a2,3
a3,3
b0,0
b1,0
b2,0
b3,0
b0,1
b1,1
b2,1
b3,1
b0,2
b1,2
b2,2
b3,2
b0,3
b1,3
b2,3
b3,3
a1,2
b1,2
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

24. S-Box Lookups a1,2: 5E S-Box 58 :b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
a1,2: 5E
S-Box 58
:b1,2

25. Shift Row Operation b0,0 b1,0 b2,0 b3,0 b0,1 b1,1 b2,1 b3,1 b0,2 b1,2
No Shift
b0,0
b0,1
b0,2
b0,3
Shift of 1
b1,1
b1,2
b1,3
b1,0
Shift of 2
b2,2
b2,3
b2,0
b2,1
Shift of 3
b3,3
b3,0
b3,1
b3,2
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

26. MixColumn Operation Matrix Multiply b0,2 c0,2 b0,0 b1,1 b2,2 b3,3 b0,1
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

27.  KeyAdd Operation c0,0 c1,1 c2,2 c3,3 c0,1 c1,2 c2,3 c3,0 c0,2 c1,3
Source: Classical and Contemporary Cryptology
by Richard J. Spillman

28. Key Generation      W(i) W(i+1) W(i+2) W(i+3) W(i+4) W(i+5)
S-Box
Rotate
Round
Constant
Source: Classical and Contemporary Cryptology
by Richard J. Spillman