Chapter 6 Computer Security Flashcards
What is the Feistel Cipher used for?
Feistel Cipher used in all symmetric block ciphers
Describe the Feistel Cipher process.
Feistel Cipher processes is 1.divide the plaintext into two halves each half have rounds of transforming in each round will apply operations include subsitiotion ,xor then after finshed rounds will combared both halves together to get a cyphertext
How does decryption work in Feistel Cipher?
Decryption is the same as encryption but uses the sub-keys in reverse order.
What operations are applied in each round of the Feistel Cipher?
Substitution is applied in each round
What is the encryption structure in Feistel Cipher?
Left half is passed to the next round.
Right half is transformed with a function and XORed with the left half to create a new right half.
What is the advantage of the Feistel Cipher?
use one algorthim for encryption and decryption
What is a block cipher?
a common symmatric encryption used by divied the plaintext into blocks with same length to produce a cyphertext with same length
Name three block ciphers discussed.
DES ,3DES, AES
What is DES mainly used for?
DES is mostly used in symmetric block ciphers.
Why is DES vulnerable to brute force?
DES use 56bit of key length it susceptible to brute-force attacks.
How many rounds does DES use?
16 rounds use
What functions are used in DES?
Substitution ,bit shift, logical operations
What is Triple DES (3DES)?
An improved version of DES, using either 2 or 3 keys for a key size of 112 or 168 bits.
What is the downside of 3DES?
Slower,Small block size;
What is AES and how does it compare to DES and 3DES?
AES is more secure and efficent than des and 3des
