Crypto

Question 1

Cipher

Answer 1

Cryptographic algo

Series of well-defined steps that we use to encrypt plaintext

Question 2

Cryptanalysis

Answer 2

Science of breaking encrypted communication

Question 3

Cryptography

Answer 3

Creating message where content is hidden

Question 4

Cryptology

Answer 4

Science of securing communication

Question 5

Confusion

Answer 5

Relationship between plaintext and ciphertext

Question 6

Diffusion

Answer 6

Order of the plaintext should be diffused (dispersed) in the cyphertext

Question 7

Symetric number of key

Answer 7

n(n-1)/2

Question 8

Asymmetric number of keys

Answer 8

2n

Question 9

3 DES which secure mode to use ?

Answer 9

K1?keymode 1

3different keyswith 112bitbkey strength

Question 10

Replacement of triple DES is ?

Answer 10

IDEA

128bit key, 64bit block size
Slower than AES and patented !

Question 11

Blowfish ?

Answer 11

Not secure
Block cypher
64bit blocks

Replaced by twofish

Question 12

Twofish ?

Answer 12

Block cypher 128bit blocks
Key length 128 , 192 or 256
Secure

Question 13

Feistel cipher

Answer 13

Plaintext block into two halves (Left and Right)

Used by a lot of cypher as DES, Twofish and 3 DES…

Question 14

RC(4-6)

Answer 14

All symetrics

Rc4 stream cypher not secured used by wep wpa ssl and tls,40-2047 bit key length

Rc5 block cypher is secured, key length 0-2040, use s feistel

Rc6?bases on rc5 128bit block ans as aes for bit key length

Question 15

Diffie-Hellman

Answer 15

DH
Securely exchange crypto key over a public channel
Earliest practical ex of public key exchange

Question 16

ECC

Answer 16

Elliptic Curve Cryptography

One way function
Asymmetric
Discret logarithms to elliptical curbes

Often on low power device as using shorter key length and be as secure

Patented
256bit key is just as strongas 3072 bit rsa key

Question 17

Rsa

Answer 17

Asymmetric

1094-4096 bit key
Slow
Patented during 1977-1997
Secure

Question 18

ElGamal

Answer 18

Asymmetric
Based on DH
Used by PGP, Gnu privacy Guard

Question 19

DSA

Answer 19

Asymmetric
Key generation has two phases
Use different algo than rsa

Question 20

MAC (Message Authentication Code)

Answer 20

Hash function using a key

Used for integrity and authenticity

Question 21

HMAC

Answer 21

Shared key with hashing

Question 22

The two uses of IPSec ?

Answer 22

1) AH: authentication header
Protect replay attack
Auth and integrity for each packet
As digital signature

2) ESP
For confidentiality
Can provide auth and integrity

Could use one of them or both

Question 23

The two mode of IPSec ?

Answer 23

Tunnel: encrypt and auth all package (headers included), for system that doesnt natively ipsec

Transport: only the payload, system that speak IPSEC

Question 24

Ipsec SA ?

Answer 24

Simplex one way like walkie talkie

Question 25

Ipsec isakmp ?

Answer 25

Handle the SA (security association) and key exchange mechanics

Question 26

IKE IPSEC ?

Answer 26

Negociate the types of encryption and hashes

Question 27

IDEA

Answer 27

Symetric block cypher
64bit cypher and 128 bit key