SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 6/05/2014 | pag. 2.

Symmetric Cryptosystems

Symmetric Cryptosystems10/04/23 | pag. 2

Block Ciphers

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Block Ciphers:Modes of Use

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• ECB: Electronic Codebook

• CBC: Cipherblock Chaining

• CFB: Cipher Feedback

• OFB: Output Feedback

Block Ciphers:Classical examples

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• Affine Cipher

• Affine Linear and Linear Cipher

• Vigenère

• Hill

We first need some linear algebra!

Intermezzo:Greatest Common Divisor

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Intermezzo:Greatest Common Divisor

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Intermezzo:Greatest Common Divisor

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Intermezzo:Greatest Common Divisor

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Intermezzo:Greatest Common Divisor

Cryptography 10/04/23 | pag. 10

Intermezzo:Euclidean Algorithm

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Intermezzo:Euclidean Algorithm

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Intermezzo:Euclidean Algorithm

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Intermezzo:Extended Euclidean Algorithm

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Intermezzo:Extended Euclidean Algorithm

Cryptography 10/04/23 | pag. 15

Intermezzo:Extended Euclidean Algorithm

Cryptography 10/04/23 | pag. 16

Intermezzo:Invertible Elements in a Residue Class Ring

Cryptography 10/04/23 | pag. 17

Intermezzo:Invertible Elements in a Residue Class Ring

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Affine Cipher

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Example:Affine Cipher

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Example: Cryptanalysis of the Affine Cipher

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Example: Cryptanalysis of the Affine Cipher

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Intermezzo:Matrices over Rings

Cryptography 10/04/23 | pag. 23

Intermezzo:Invertible Matrices

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Intermezzo:Invertible Matrices

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Intermezzo:Invertible Matrices

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Intermezzo:Invertible Matrices

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Intermezzo:Affine Linear Functions

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Intermezzo:Affine Linear Functions

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Affine Linear Cipher

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Affine Linear Cipher

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