contact information cryptography 8/10/2015 | pag. 2 professor assistant office webpage course text...
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Contact Information
Cryptography 21/04/23 | pag. 2
Professor
Assistant
Office
Webpage
Course Text
Adriaan [email protected]
Pleinlaan 9, 2.29
http://homepages.vub.ac.be/~andooms (Education)
• Johanes A. Buchmann. Introduction to Cryptography, Springer, 2000.• Richard Mollin, Codes: The Guide to Secrecy From Ancient to Modern Times, Chapman & Hall, 2005. • Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone Handbook of Applied Cryptography, CRC Press, 1996.
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Introduction
Introduction21/04/23 | pag. 3
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Cryptology
Introduction21/04/23 | pag. 4
Cryptology
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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.
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Cryptography
Cryptanalysis
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Cryptosystem
Introduction21/04/23 | pag. 5
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Example: Ceasar Cipher
Cryptography 21/04/23 | pag. 6
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Example: Ceasar Cipher
Introduction21/04/23 | pag. 7
Hence the number of keys should be large!
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Basic Concepts
Introduction21/04/23 | pag. 8
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Symmetric vs AsymmetricCryptosystems
Introduction21/04/23 | pag. 9
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Cryptanalysis
Introduction21/04/23 | pag. 10
Kerckhoff’s principle
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Attacks
Introduction21/04/23 | pag. 11
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Example: Attacks
Introduction21/04/23 | pag. 12
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Alphabet
Introduction21/04/23 | pag. 13
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Alphabet
Introduction21/04/23 | pag. 14
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Words
Introduction21/04/23 | pag. 15
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Permutations
Introduction21/04/23 | pag. 16
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Permutations
Cryptography 21/04/23 | pag. 17
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Symmetric Cryptosystems
Symmetric Cryptosystems21/04/23 | pag. 18
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Block Ciphers
Symmetric Cryptosystems21/04/23 | pag. 19
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Block Ciphers
Symmetric Cryptosystems21/04/23 | pag. 20
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Block Ciphers:Permutation Cipher
Symmetric Cryptosystems21/04/23 | pag. 21
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Block Ciphers:Multiple Encryption
Symmetric Cryptosystems21/04/23 | pag. 22
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Block Ciphers:Modes of Use
Cryptography 21/04/23 | pag. 23
• ECB: Electronic Codebook
• CBC: Cipherblock Chaining
• CFB: Cipher Feedback
• OFB: Output Feedback
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Block Ciphers – ECB:Electronic Codebook Mode
Cryptography 21/04/23 | pag. 24
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Block Ciphers – ECB:Electronic Codebook Mode
Cryptography 21/04/23 | pag. 25
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Block Ciphers – ECB:Electronic Codebook Mode
Cryptography 21/04/23 | pag. 26
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Example:Block Ciphers – ECB
Cryptography 21/04/23 | pag. 27
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Drawback:Block Ciphers – ECB
Cryptography 21/04/23 | pag. 28
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Example:Block Ciphers – ECB
Cryptography 21/04/23 | pag. 29
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Block Ciphers – CBC:Cipherblock Chaining Mode
Cryptography 21/04/23 | pag. 30
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Block Ciphers – CBC:XOR
Cryptography 21/04/23 | pag. 31
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Block Ciphers – CBC:Cipherblock Chaining Mode
Cryptography 21/04/23 | pag. 32
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Block Ciphers – CBC:Cipherblock Chaining Mode
Cryptography 21/04/23 | pag. 33
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Block Ciphers – CBC:Cipherblock Chaining Mode
Cryptography 21/04/23 | pag. 34
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Example:Block Ciphers – CBC
Cryptography 21/04/23 | pag. 35
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Block Ciphers – CBC:Cipherblock Chaining Mode
Cryptography 21/04/23 | pag. 36
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Example:Block Ciphers – CBC
Cryptography 21/04/23 | pag. 37
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Drawback:Block Ciphers – CBC
Cryptography 21/04/23 | pag. 38
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Block Ciphers – CFB:Cipher Feedback Mode
Cryptography 21/04/23 | pag. 39
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Block Ciphers – CFB:Cipher Feedback Mode
Cryptography 21/04/23 | pag. 40
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Block Ciphers – CFB:Cipher Feedback Mode
Cryptography 21/04/23 | pag. 41
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Example:Block Ciphers – CFB
Cryptography 21/04/23 | pag. 42
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Drawback:Block Ciphers – CFB
Cryptography 21/04/23 | 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.
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Block Ciphers – OFB:Output Feedback Mode
Cryptography 21/04/23 | pag. 44
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Block Ciphers – OFB:Output Feedback Mode
Cryptography 21/04/23 | pag. 45
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Block Ciphers – OFB:Output Feedback Mode
Cryptography 21/04/23 | pag. 46
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Example:Block Ciphers – OFB
Cryptography 21/04/23 | pag. 47
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Drawback:Block Ciphers – OFB
Cryptography 21/04/23 | pag. 48