Transcript Fractale & Wavelet Beeldcompressie

Contact Information
Professor Ann Dooms
[email protected]
Assistant Adriaan Barri
[email protected]
Office Pleinlaan 9, 2.29
Webpage http://homepages.vub.ac.be/~andooms (Education)
Course • Johanes A. Buchmann.
Text 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.
Cryptography
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INTRODUCTION
Introduction
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Cryptology
Cryptography
A form of communication which is primarily
concerned with the secure transmission
(through encryption) of a secret message
over an insecure channel.
+
Cryptanalysis
Deals with attacks on encrypted intercepted
messages to recover the secret message.
=
Introduction
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Cryptology
Cryptosystem
Introduction
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Example:
Ceasar Cipher
Cryptography
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Example:
Ceasar Cipher
Hence the number of keys should be large!
Introduction
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BASIC CONCEPTS
Introduction
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Symmetric vs Asymmetric
Cryptosystems
Introduction
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Cryptanalysis
Kerckhoff’s principle
Introduction
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Attacks
Introduction
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Example:
Attacks
Introduction
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Alphabet
Introduction
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Alphabet
Introduction
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Words
Introduction
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Permutations
Introduction
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Permutations
Cryptography
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SYMMETRIC
CRYPTOSYSTEMS
Symmetric Cryptosystems
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Block Ciphers
Symmetric Cryptosystems
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Block Ciphers
Symmetric Cryptosystems
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Block Ciphers:
Permutation Cipher
Symmetric Cryptosystems
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Block Ciphers:
Multiple Encryption
Symmetric Cryptosystems
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Block Ciphers:
Modes of Use
• ECB: Electronic Codebook
• CBC: Cipherblock Chaining
• CFB: Cipher Feedback
• OFB: Output Feedback
Cryptography
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Block Ciphers – ECB:
Electronic Codebook Mode
Cryptography
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Block Ciphers – ECB:
Electronic Codebook Mode
Cryptography
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Block Ciphers – ECB:
Electronic Codebook Mode
Cryptography
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Example:
Block Ciphers – ECB
Cryptography
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Drawback:
Block Ciphers – ECB
Cryptography
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Example:
Block Ciphers – ECB
Cryptography
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Block Ciphers – CBC:
Cipherblock Chaining Mode
Cryptography
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Block Ciphers – CBC:
XOR
Cryptography
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Block Ciphers – CBC:
Cipherblock Chaining Mode
Cryptography
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Block Ciphers – CBC:
Cipherblock Chaining Mode
Cryptography
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Block Ciphers – CBC:
Cipherblock Chaining Mode
Cryptography
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Example:
Block Ciphers – CBC
Cryptography
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Block Ciphers – CBC:
Cipherblock Chaining Mode
Cryptography
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Example:
Block Ciphers – CBC
Cryptography
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Drawback:
Block Ciphers – CBC
Cryptography
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Block Ciphers – CFB:
Cipher Feedback Mode
Cryptography
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Block Ciphers – CFB:
Cipher Feedback Mode
Cryptography
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Block Ciphers – CFB:
Cipher Feedback Mode
Cryptography
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Example:
Block Ciphers – CFB
Cryptography
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Drawback:
Block Ciphers – CFB
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.
Cryptography
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Block Ciphers – OFB:
Output Feedback Mode
Cryptography
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Block Ciphers – OFB:
Output Feedback Mode
Cryptography
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Block Ciphers – OFB:
Output Feedback Mode
Cryptography
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Example:
Block Ciphers – OFB
Cryptography
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Drawback:
Block Ciphers – OFB
Cryptography
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