Contact Information Cryptography 8/10/2015 | pag. 2 Professor Assistant Office Webpage Course Text Ann Dooms Adriaan Barri

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Presentation transcript:

Contact Information Cryptography 8/10/2015 | pag. 2 Professor Assistant Office Webpage Course Text Ann Dooms Adriaan Barri Pleinlaan 9, (Education) Johanes A. Buchmann. Introduction to Cryptography, Springer, Richard Mollin, Codes: The Guide to Secrecy From Ancient to Modern Times, Chapman & Hall, Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone Alfred J. MenezesPaul C. van OorschotScott A. Vanstone Handbook of Applied Cryptography, CRC Press, 1996.Handbook of Applied Cryptography

INTRODUCTION Introduction 8/10/2015 | pag. 3

Cryptology Introduction 8/10/2015 | pag. 4 Cryptology + A form of communication which is primarily concerned with the secure transmission (through encryption) of a secret message over an insecure channel. Deals with attacks on encrypted intercepted messages to recover the secret message. = Cryptography Cryptanalysis

Cryptosystem Introduction 8/10/2015 | pag. 5

Example: Ceasar Cipher Cryptography 8/10/2015 | pag. 6

Example: Ceasar Cipher Introduction 8/10/2015 | pag. 7 Hence the number of keys should be large!

BASIC CONCEPTS Introduction 8/10/2015 | pag. 8

Symmetric vs Asymmetric Cryptosystems Introduction 8/10/2015 | pag. 9

Cryptanalysis Introduction 8/10/2015 | pag. 10 Kerckhoff’s principle

Attacks Introduction 8/10/2015 | pag. 11

Example: Attacks Introduction 8/10/2015 | pag. 12

Alphabet Introduction 8/10/2015 | pag. 13

Alphabet Introduction 8/10/2015 | pag. 14

Words Introduction 8/10/2015 | pag. 15

Permutations Introduction 8/10/2015 | pag. 16

Permutations Cryptography 8/10/2015 | pag. 17

SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 8/10/2015 | pag. 18

Block Ciphers Symmetric Cryptosystems 8/10/2015 | pag. 19

Block Ciphers Symmetric Cryptosystems 8/10/2015 | pag. 20

Block Ciphers: Permutation Cipher Symmetric Cryptosystems 8/10/2015 | pag. 21

Block Ciphers: Multiple Encryption Symmetric Cryptosystems 8/10/2015 | pag. 22

Block Ciphers: Modes of Use Cryptography 8/10/2015 | pag. 23 ECB: Electronic Codebook CBC: Cipherblock Chaining CFB: Cipher Feedback OFB: Output Feedback

Block Ciphers – ECB: Electronic Codebook Mode Cryptography 8/10/2015 | pag. 24

Block Ciphers – ECB: Electronic Codebook Mode Cryptography 8/10/2015 | pag. 25

Block Ciphers – ECB: Electronic Codebook Mode Cryptography 8/10/2015 | pag. 26

Example: Block Ciphers – ECB Cryptography 8/10/2015 | pag. 27

Drawback: Block Ciphers – ECB Cryptography 8/10/2015 | pag. 28

Example: Block Ciphers – ECB Cryptography 8/10/2015 | pag. 29

Block Ciphers – CBC: Cipherblock Chaining Mode Cryptography 8/10/2015 | pag. 30

Block Ciphers – CBC: XOR Cryptography 8/10/2015 | pag. 31

Block Ciphers – CBC: Cipherblock Chaining Mode Cryptography 8/10/2015 | pag. 32

Block Ciphers – CBC: Cipherblock Chaining Mode Cryptography 8/10/2015 | pag. 33

Block Ciphers – CBC: Cipherblock Chaining Mode Cryptography 8/10/2015 | pag. 34

Example: Block Ciphers – CBC Cryptography 8/10/2015 | pag. 35

Block Ciphers – CBC: Cipherblock Chaining Mode Cryptography 8/10/2015 | pag. 36

Example: Block Ciphers – CBC Cryptography 8/10/2015 | pag. 37

Drawback: Block Ciphers – CBC Cryptography 8/10/2015 | pag. 38

Block Ciphers – CFB: Cipher Feedback Mode Cryptography 8/10/2015 | pag. 39

Block Ciphers – CFB: Cipher Feedback Mode Cryptography 8/10/2015 | pag. 40

Block Ciphers – CFB: Cipher Feedback Mode Cryptography 8/10/2015 | pag. 41

Example: Block Ciphers – CFB Cryptography 8/10/2015 | pag. 42

Drawback: Block Ciphers – CFB Cryptography 8/10/2015 | pag. 43 The smaller the block length r, the shorter the ciphertext blocks. This means on the hand that transmission is faster, but on the other hand that the block encryption function must be applied more frequently. The optimal choice of r depends on a tradeoff between transmission and computation speed.

Block Ciphers – OFB: Output Feedback Mode Cryptography 8/10/2015 | pag. 44

Block Ciphers – OFB: Output Feedback Mode Cryptography 8/10/2015 | pag. 45

Block Ciphers – OFB: Output Feedback Mode Cryptography 8/10/2015 | pag. 46

Example: Block Ciphers – OFB Cryptography 8/10/2015 | pag. 47

Drawback: Block Ciphers – OFB Cryptography 8/10/2015 | pag. 48