SYMMETRIC
CRYPTOSYSTEMS
Symmetric Cryptosystems
21/12/2015 | pag. 2
Block Ciphers
Symmetric Cryptosystems
21/12/2015 | pag. 3
Block Ciphers:
Modes of Use
• ECB: Electronic Codebook
• CBC: Cipherblock Chaining
• CFB: Cipher Feedback
• OFB: Output Feedback
Cryptography
21/12/2015 | pag. 4
Block Ciphers:
Classical examples
• Affine Cipher
• Affine Linear and Linear Cipher
• Vigenère
• Hill
We first need some linear algebra!
Symmetric Cryptosystems
21/12/2015 | pag. 5
Intermezzo:
Greatest Common Divisor
Symmetric Cryptosystems
21/12/2015 | pag. 6
Intermezzo:
Greatest Common Divisor
Symmetric Cryptosystems
21/12/2015 | pag. 7
Intermezzo:
Greatest Common Divisor
Symmetric Cryptosystems
21/12/2015 | pag. 8
Intermezzo:
Greatest Common Divisor
Symmetric Cryptosystems
21/12/2015 | pag. 9
Intermezzo:
Greatest Common Divisor
Cryptography
21/12/2015 | pag. 10
Intermezzo:
Euclidean Algorithm
Cryptography
21/12/2015 | pag. 11
Intermezzo:
Euclidean Algorithm
Cryptography
21/12/2015 | pag. 12
Intermezzo:
Euclidean Algorithm
Cryptography
21/12/2015 | pag. 13
Intermezzo:
Extended Euclidean Algorithm
Cryptography
21/12/2015 | pag. 14
Intermezzo:
Extended Euclidean Algorithm
Cryptography
21/12/2015 | pag. 15
Intermezzo:
Extended Euclidean Algorithm
Cryptography
21/12/2015 | pag. 16
Intermezzo:
Invertible Elements in a Residue Class Ring
Cryptography
21/12/2015 | pag. 17
Intermezzo:
Invertible Elements in a Residue Class Ring
Cryptography
21/12/2015 | pag. 18
Affine Cipher
Symmetric Cryptosystems
21/12/2015 | pag. 19
Example:
Affine Cipher
Symmetric Cryptosystems
21/12/2015 | pag. 20
Example:
Cryptanalysis of the Affine Cipher
Symmetric Cryptosystems
21/12/2015 | pag. 21
Example:
Cryptanalysis of the Affine Cipher
Symmetric Cryptosystems
21/12/2015 | pag. 22
Intermezzo:
Matrices over Rings
Cryptography
21/12/2015 | pag. 23
Intermezzo:
Invertible Matrices
Cryptography
21/12/2015 | pag. 24
Intermezzo:
Invertible Matrices
Cryptography
21/12/2015 | pag. 25
Intermezzo:
Invertible Matrices
Cryptography
21/12/2015 | pag. 26
Intermezzo:
Invertible Matrices
Cryptography
21/12/2015 | pag. 27
Intermezzo:
Affine Linear Functions
Cryptography
21/12/2015 | pag. 28
Intermezzo:
Affine Linear Functions
Cryptography
21/12/2015 | pag. 29
Affine Linear Cipher
Cryptography
21/12/2015 | pag. 30
Affine Linear Cipher
Cryptography
21/12/2015 | pag. 31