Symmetric Cryptography 2 - CTR, OFB, CBC, etc ...

Question 1

if numbers are same result is “0”, if numbers are different result is “1”.

Answer 1

XOR

Question 2

symmetric algorithm, feistel function, splits block on plaintext in 2 parts (L0/R0), round function is applied to one half and round function is performed on one half, output is then XOR’d w/other half, for 16 rounds.

Answer 2

DES (symmetric algorithm)

Question 3

symmetric algorithm, different from DES because AES uses 4x4 matrix of bytes, called state, also called substitution permutation matrix.

Answer 3

AES (symmetric algorithm)

Question 4

symmetric algorithm, has 4 modes -> ECB : 64-bit block entered into and block cipher text is produced, if last full padding is added, used for small amounts of data, creates patterns, considered weak.

Answer 4

DES (symmetric algorithm)

Question 5

used for large amounts of data, uses 64 bit blocks of data, but inserts bits from previous cipher text block, uses XORing, IV.

Answer 5

CBC

Question 6

emulates a stream cipher turns block cipher into stream cipher, bits to encrypt the next block come from ciphertext of proceeding block using XORed w/plaintext to produce current ciphertext block, encrypts individual characters, uses chaining as in CBC.

Answer 6

CFB

Question 7

turns block cipher into stream cipher, XORed w/plaintext blocks to generate ciphertext, great for digital data and signal transmission, errors do not propagate, IV is used to create seed value for next encrypted block.

Answer 7

OFB

Question 8

turns block cipher into stream cipher, generates next keystream block by encrypting successive values of a counter that do not repeat for long, IV increments in value for every packet in message instead of whole message.

Answer 8

CTR

Question 9

symmetric algorithm, key whitening, XOR a key w/text before round function after or both, uses 48 rounds.

Answer 9

DESx (symmetric algorithm)