P2L6: Symmetric Encryption Flashcards
What does confusion mean regarding encryption and how is it achieved?
* It is an encryption operation where the relationship between the key and cipher text is obscured * Generally achieved through substitution
What is diffusion in encryption?
* In an encryption operation where the influence of one plaintext data is spread over many ciphertext bits with the goal of hiding statistical properties of the plaintext * Generally achieved through permutations
What are rounds in ciphertext encryption?
diffusion and confusion by themselves aren’t enough, but after being applied multiple times through many rounds they are hard to crack
How many bits is the key in DES?
64 bits, but only 56 are used for data
What is the value length in DES?
* The key is 64 bits, but the value is only 56 bits since there are the parity bits * 64 bit input = 64 bit output
Mangler function performs both substitution and permutations. True/False
True
What are the problems with DES?
* Keyspace is too small and can be broken with today’s brute force computers. Just a 56-bit key. * S-box design criteria has been kept a secret and hasn’t been able to be reviewed.
What is Triple DES?
It is a way to secure DES by running it three times (effectively making a longer key)
What key lengths are possible with DES?
56, 112, and 168
What key lengths are possible with AES?
128, 192 and 256
What are the problems with the Electronic Code Book method?
* Doesn’t provide strong confidentiality protection since cryptanalysis can be used on repetitive blocks * Don’t defend against integrity attacks
What is the current way to encrypt a large message? How does it work? How many keys are involved?
* CBC (Cipher-Block Chaining) * CBC encryption works by XOR’ing the previous ciphertext block with the next ciphertext block * Use 2 keys
CBC is more secure than ECB. True/False
True
