Cryptography

Question 1

Message written on cloth is wrapped on certain size stick. By itself it is nothing, wrapped around another stick the same diameter, it is decipherable

Answer 1

Spartan scytale

Question 2

This cipher switches letters by a certain number of spots, with the goal of substitution

Answer 2

Caesar cipher

Question 3

A polyalphabetic cipher. It forms a matrix also known as the Vigenere Square. Uses plaintext (x axis) and a key (y axis) to decipher.

Answer 3

Vigenere cipher

Question 4

Cryptography uses ____ math

Answer 4

modular

Question 5

Science of securing communications

Answer 5

Cryptology

Question 6

Creates messages where the meaning is hidden

Answer 6

Cryptography

Question 7

Science of breaking encrypted communications

Answer 7

Cryptanalysis

Question 8

A cryptographic algorithm

Answer 8

Cipher

Question 9

This cipher is a well-known text known as a key. It is symmetric.

Answer 9

Book cipher

Question 10

This cipher uses a phrase to encrypt/decrypt a message

Answer 10

Running-key cipher

Question 11

This cipher substitutes one letter for another and is easy to break

Answer 11

Monoalphabetic cipher

Question 12

This cipher is similar to Monoalphabetic cipher except it starts at a different point each round it rotates

Answer 12

Polyalphabetic cipher

Question 13

Looking at frequency of a certain character

Answer 13

Frequency analysis

Question 14

This cipher deals with 1s and 0s to encrypt a message

Answer 14

XOR

Question 15

In XOR, 0=0 would be which? (1 or 0)

Answer 15

0, same equals 0

different equals 1

Question 16

In XOR, 1=0 would be which? (1 or 0)

Answer 16

1, different equals 1

same equals 0

Question 17

XOR must have which four attributes to be successful?

Answer 17

Confusion, Diffusion, Substitution, Permutation

Question 18

A project between US and UK to break russian encryption in 1943. The KGB used one time pads for sensitive transmissions. The KGB also reused pads which led to many messages being decoded.

Answer 18

Project Venon

Question 19

Unbreakable encryption if implemented correctly and can only be used once

Answer 19

One time pads

Question 20

First known cipher to use one time pad

Answer 20

Vernam cipher

Question 21

Used set of wheels or disks, each with 26 letters of the alphabet. Jefferson (US president) invented it and Bazeries approved it. The order of the disk is the cipher key and both sender and receiver must arrange disk in same predefined order.

Answer 21

Jefferson disk

Question 22

Committee that prevented export of ‘critical tech’ (aka cryptography) from ‘western’ countries to the ‘iron curtain’ during the cold war.

Answer 22

COCOM

Question 23

Similar to COCOM but now includes ‘iron curtain’ countries after war

Answer 23

Wasssenaar Arrangement

Question 24

What is the formula for symmetric encryption to find total number of keys needed?

Answer 24

n(n-1)/2, with n = users

Question 25

What is the formula for asymmetric encryption to find total number of keys needed?

Answer 25

2 x users

Question 26

DES is what type of encryption?

Answer 26

Symmetric

Question 27

DES cipher and key length?

Answer 27

64 bit block cipher, 56 bit key, 16 rounds of encryption and uses Fistel cipher

Question 28

What are the 5 modes of DES?

Answer 28

ECB, CBC, CFB, OFB, CTR

Question 29

Describe ECB (electronic code book) in regards to DES

Answer 29

A mode of DES encryption Simplest and weakest mode No initialization vector or chaining

Question 30

Describe CBC (cipher block chaining) in regards to DES

Answer 30

Uses initialization vectors and chaining First block uses initialization vector and every subsequent block uses XOR from first block The weakness is an encryption error which will propagate through all block after the error since they build on each other, breaking integrity

Question 31

Describe CFB (cipher feedback) in regards to DES

Answer 31

Similar to CBC except uses stream cipher, not block.

Question 32

Describe OFB (output feedback) in regards to DES

Answer 32

Similar to CFB but instead uses the previous ciphertext for the XOR it uses the subkey before it is XOR’d to the plaintext

Question 33

Describe CTR (counter) in regards to DES

Answer 33

Similar to OFB but uses the feedback differently. It can be as simple as ascending numbers. Ex: first block XOR’d with 1, second block with 2, third block with 3

Question 34

3DES type, cipher, and key length?

Answer 34

Symmetric, 64 bit block cipher, 112 or 168 bit key

Question 35

IDEA type, cipher, and key length?

Answer 35

Symmetric, 128 bit key, 64 bit block size

Question 36

AES type and key length?

Answer 36

Symmetric, key sized is based on the number of cycles 10 cycles for 128 bit keys 12 cycles for 192 bit keys 14 cycles for 256 bit keys

Question 37

This encryption algorithm is symmetric, open source, and considered secure

Question 38

What are the Rounds and substeps in each round for AES encryption?

Answer 38

1. Initial round AddRoundKey: each byte is combined with a block of the round key using bitwise XOR 2. Rounds - SubBytes: a non-linear substitution step where each byte is replaced with another according to a lookup table - ShiftRows: a transposition step where the last three rows of the state are shifted a certain number of steps - MixColumns: a mixing operation which operates on the columns, combining the four bytes in each column 3. Final Round - Does all steps in Rounds minus the MixColumns step

Question 39

Blowfish type, cipher, and key length?

Answer 39

Symmetric, block cipher, 64-bit blocks, 32-448 bit key length, Feistel cipher No longer considered secure

Question 40

Twofish type, cipher, and key length?

Answer 40

Symmetric, block cipher, 128-bit blocks, 128, 192, 256 bit key length, Feistel cipher Considered secure

Question 41

Describe how the Feistel Cipher works?

Answer 41

Splits a plaintext block in 2 halves (left and right) The process goes through several round, the right half of the block does not change The right half is XOR’d with a subkey for each round The XOR’d value is then XOR’d with the left block The recipient reverses the subkey order and XORs to get the plaintext

Question 42

Feistel Cipher is related to what type of encryption?

Answer 42

Symmetric

Question 43

What encryption does this describe? Used by WEP/WPA/SSL/TLS Symmetric, stream cipher, 40- 2048 bit key length No longer secure

Answer 43

RC4

Question 44

Symmetric, 32, 64, or 128 bit blocks, 0-2040 bit key length Considered secure (if high enough blocks/keys)

Answer 44

RC5

Question 45

Symmetric, block cipher, 128-bit blocks, 128, 192 and 256 key length Considered secure

Answer 45

RC6

Question 46

This type of encryption uses 2 keys, a private and a public.

Answer 46

Asymmetric

Question 47

RSA type and key length?

Answer 47

Asymmetric, 1094-4096 bit key Considered secure

Question 48

First asymmetric encryption to be used publicly and on the internet

Answer 48

Diffie-Hellman

Question 49

This assymmetric encryption allows two users with no prior knowledge of each other to establish a shared secret key over an insecure channel

Answer 49

Diffie-Hellman

Question 50

This encryption uses discrete logarithms applied to elliptical curves

Answer 50

Elliptic Curve Cryptography (ECC)

Question 51

An asymmetric encryption based on Diffie hellman used in free GNU software

Answer 51

ElGamal

Question 52

This encryption is assymmetric and generates keys in two phases 1. algorithm parameters which is shared between different users 2. Computes public and private keys for single user

Answer 52

DSA (Digital Signature Algorithm)

Question 53

This encryption is asymmetric and uses the public key ONLY for encryption and private ONLY for decryption, making it unusable for non-repudiation and authentication

Answer 53

Knapsack