Block Ciphers Modes of Operation Quiz
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Questions and Answers

What type of encryption uses different keys for encryption and decryption?

  • Vernam Cipher
  • Symmetric key encryption
  • Asymmetric key encryption (correct)
  • Caesar Cipher

    • Which type of cipher replaces each character with another character a fixed number of positions down the alphabet?

  • Substitution Cipher (correct)
  • Vigenère cipher
  • Vernam Cipher
  • Hill Cipher

    • What does AES stand for in the context of cryptography?

  • Advanced Encryption Standard (correct)
  • Advanced Encoding System
  • Asymmetric Encryption Standard
  • Altered Encoding Scheme

    • Which type of attack analyzes how differences in input can affect the resulting encrypted output?

    <p>Differential Cryptanalysis</p> Signup and view all the answers

    What must hold true for a One Time Pad (OTP) to be secure?

    <p>The key must be randomly generated and as long as the plaintext</p> Signup and view all the answers

    Which type of cipher operates on fixed-size blocks of data, rather than manipulating individual characters?

    <p>Block Ciphers</p> Signup and view all the answers

    What property does AES shiftRows and shiftColumns step ensure according to the text?

    <p>Diffusion</p> Signup and view all the answers

    What is the main focus of Linear Cryptanalysis on block ciphers like DES, 3DES, and AES?

    <p>Constructing linear equations with high bias</p> Signup and view all the answers

    What does Differential Cryptanalysis study in relation to block ciphers?

    <p>The distribution of differences in ciphertexts from known plaintexts</p> Signup and view all the answers

    Which feature characterizes a Cryptographic Hash Function (CHF) based on the text?

    <p>Ability to map data to a fixed-size bit array</p> Signup and view all the answers

    In Cryptographic Hash Function SHA-256, what does 'SHA' stand for?

    <p>Secure Hash Algorithm</p> Signup and view all the answers

    What is the primary goal of MixColumns in AES in conjunction with ShiftRows?

    <p>Creating diffusion in the cipher</p> Signup and view all the answers

    What is the main difference between ECB and CBC modes of operation in block ciphers?

    <p>In ECB mode, each encryption block operation is independent of adjacent blocks, while in CBC mode, each encryption block operation is dependent on adjacent blocks.</p> Signup and view all the answers

    Why did the National Institute of Standards and Technology (NIST) replace DES with AES as the standard encryption algorithm?

    <p>DES was vulnerable to cracking, while AES provided increased security against attacks like differential and linear cryptanalysis.</p> Signup and view all the answers

    Which mode of operation in block ciphers results in identical ciphertext blocks when encrypting identical plaintext blocks with the same key?

    <p>ECB (Electronic Code Book)</p> Signup and view all the answers

    What made cracking the DES algorithm possible in the 1990s?

    <p>Advances in differential and linear cryptanalysis techniques.</p> Signup and view all the answers

    Which block cipher mode of operation partially depends on adjacent blocks during encryption?

    <p>CTR (Counter)</p> Signup and view all the answers

    Why was DES originally practical only in hardware implementations?

    <p>DES was designed to be faster in hardware implementations than software implementations.</p> Signup and view all the answers

    Study Notes

    Asymmetric Encryption

    • Asymmetric encryption uses different keys for encryption and decryption.

    Caesar Cipher

    • Caesar Cipher replaces each character with another character a fixed number of positions down the alphabet.

    Advanced Encryption Standard (AES)

    • AES stands for Advanced Encryption Standard in the context of cryptography.

    Differential Attack

    • Differential attack analyzes how differences in input can affect the resulting encrypted output.

    One-Time Pad (OTP)

    • For a One-Time Pad (OTP) to be secure, the key must be at least as long as the plaintext, never reused, and kept secret.

    Block Cipher

    • Block Cipher operates on fixed-size blocks of data, rather than manipulating individual characters.

    AES ShiftRows and ShiftColumns

    • AES ShiftRows and shiftColumns step ensures the mixing of columns and diffusion of rows.

    Linear Cryptanalysis

    • The main focus of Linear Cryptanalysis is on finding linear approximations of the block cipher's nonlinear components, such as S-boxes, in block ciphers like DES, 3DES, and AES.

    Differential Cryptanalysis

    • Differential Cryptanalysis studies how pairs of inputs with a fixed difference in plaintext produce a fixed difference in ciphertext in relation to block ciphers.

    Cryptographic Hash Function (CHF)

    • A Cryptographic Hash Function (CHF) feature is that it is deterministic, non-invertible, and collision-resistant.

    SHA-256

    • In Cryptographic Hash Function SHA-256, 'SHA' stands for Secure Hash Algorithm.

    MixColumns in AES

    • The primary goal of MixColumns in AES, in conjunction with ShiftRows, is to ensure diffusion of columns.

    ECB and CBC Modes

    • The main difference between ECB and CBC modes of operation in block ciphers is that ECB does not use an initialization vector (IV), while CBC does.

    NIST and AES

    • The National Institute of Standards and Technology (NIST) replaced DES with AES as the standard encryption algorithm due to DES's vulnerability to brute-force attacks.

    ECB Mode

    • ECB mode of operation in block ciphers results in identical ciphertext blocks when encrypting identical plaintext blocks with the same key.

    DES Cracking

    • Cracking the DES algorithm was made possible in the 1990s due to its small key size, making it vulnerable to brute-force attacks.

    CBC Mode

    • CBC mode of operation in block ciphers partially depends on adjacent blocks during encryption.

    DES Original Practicality

    • DES was originally practical only in hardware implementations because its computational requirements were too high for software implementations at the time.

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    Description

    Test your knowledge on various modes of operation in block ciphers such as ECB, CBC, and CTR. Understand how different methods combine block operations for encryption and decryption, and the characteristics of Electronic Code Book mode.

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