Quiz 1

Question 1

Cryptanalysis

Answer 1

trying to break encryption

Question 2

Cryptanalysis Types

Answer 2

Differential and Linear

Question 3

What is Differential Cryptanalysis?

Answer 3

Used to analyze block ciphers

compares 2 related pairs of encryptions

Question 4

What is Linear Cryptanalysis?

Answer 4

Use a large number of trial encryptions

Question 5

Types of attacks on Cryptography?

Answer 5

• Ciphertext only
• Chosen Plaintext/ciphertext/text

Question 6

What is a substitution cipher?

Answer 6

units of plaintext are replaced with ciphertext

Question 7

Types of substitution cipher?

Answer 7

monoalphabetic and polyalphabetic

Question 8

monoalphabetic cipher

Answer 8

uses fixed substitution over the entire message

Question 9

polyalphabetic cipher

Answer 9

uses a number of substitutions at different positions in the message

Question 10

Ex of monoalphabetic Cipher

Answer 10

Ceasar Cipher

Question 11

Ex of polyalphabetic Cipher

Answer 11

Vignere Table

Question 12

transposition cipher

Answer 12

plaintext are rearranged in a different and usually quite complex order

Question 13

Columnar

Answer 13

characters rearranged into columns

Ex) transposition cipher

Question 14

Perfect Substitution Cipher

Answer 14

uses a one time pad for encryption ex) Vernam Cipher

Question 15

Unbreakable Cipher

Answer 15

uses vignere table with 1 time key and 2 decryption types with 2 keys

Question 16

Block vs Stream Ciphers

Answer 16

Stream-convert a symbol into plain text (mono/polyalphabetic) Block-groups of plaintext (Colmnar and fractioned morse)

Question 17

S-Permutation

Answer 17

uses s and p boxes

Question 18

Feistel Cipher

Answer 18

block of 2 halves that process multiple rounds, perform substitution, then swap halves

Question 19

Design principles of feistel cipher

Answer 19

Block size, Key size, # rounds, Subkey generation, Round function, Fast soft encrypt/decryption

Question 20

What is DES?

Answer 20

Type of block cipher that uses a 56 bit key to encrypt 64 bits of data (concern with key size)

Outline:

• split data in half
• scramble each half indep
• combine key with one half
• swap the two halves
• repeat the process 16 times

Question 21

Avalanche Effect

Answer 21

change to 1 input or key results in ½ output bits

Question 22

DES variants

Answer 22

• Multiple DES
• Triple DES
• DES with Indep subkeys
• DESX CRYPT3
• Generalized DES
• DES with Alternative S-Box
• DES with key dependent S-Box