Cryptography Extra 4

Question 1

number that has no factors in common w/another number (ex: 3, 7)

Answer 1

co-prime numbers

Question 2

N1 + N2 = N3, so 0 + 1= 1, 1 + 2 = 3, etc …

Answer 2

Fibonacci Numbers

Question 3

high probability of a collision = birthday paradox. Birthday attack : attempt to find collision for a given hash.

*** MQV : protocol based on DH for key agreement.

Answer 3

info …

Question 4

has generator seeded produce pseudo-random data, entropy accumulator collects random data from various sources and uses that to reseed generator, seed file which has initial seed values.

Answer 4

Fortuna

Question 5

alice wants to know message came from bob, bob uses his own private key, anyone receiving message can use bobs public key to decrypt message, if it works then it must have been signed w/Bob’s private key.

Answer 5

Digital Signatures

Question 6

each block of plaintext is XORed w/previous ciphertext block before being encrypted. More randomness in final ciphertext.

Answer 6

CBC

Question 7

cause small changes in ciphertext to propagate indefinitely when decrypting and encrypting.

Answer 7

PCBC

Question 8

previous ciphertext block is encrypted then the ciphertext produced is XORed back w/plaintext to produce current ciphertext block. Increases randomness.

Answer 8

CFB

Question 9

turns block cipher into synchronous stream cipher, it generates keystream blocks which are XORed w/plaintext blocks to get ciphertext.

Answer 9

OFB

Question 10

also turns block cipher into stream cipher, generates next keystream block by encrypting successive values of a counter which doesnt repeat for a long time.

Answer 10

CTR