Cryptography Extra 2 + Binary AND / OR / XOR Flashcards Preview

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Flashcards in Cryptography Extra 2 + Binary AND / OR / XOR Deck (10)
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1
Q

A cryptosystem should be secure even if everything about the system, except the key, is publically known.

A

Kerckhoff’s Principle

2
Q

C = E(k,p)

A

Symmetric Encryption Algorithm

3
Q

P = E(k,c)

A

Symmetric Decryption Algorithm

4
Q

changing some part of plaintext for some matching part of ciphertext. Caesar and Atbash are simple substitution ciphers, and so is the more complex Vigenere.

A

Substitution

5
Q

swapping of blocks of ciphertext.

A

Transposition

6
Q

1 1 0 1
1 0 0 1
________ Binary AND
? ? ? ?

A

Binary AND : if both numbers have a one in both places, then the result number is a one, if not then the number is zero

1101
1001
——–
1001

7
Q

1 1 0 1
1 0 0 1
________ Binary OR
? ? ? ?

A

Binary OR : if a 1 is in either or both numbers in a give place then result is 1, if not result is 0.

1101
1001
——-
1101

8
Q

1 1 0 1
1 0 0 1
________ Binary XOR
? ? ? ?

A

Binary XOR : if a 1 is in one number and not the other the result is 1, if not the result is zero.

1101
1001
——-
0100

9
Q

larger block size increase security, larger key size increase security, if round function is secure then more rounds increase security. Key space refers to the number of possible keys. For example, DES uses a 56-bit key so it has a key space of 2^56. Key : random bits used in encrypting a message. Key schedule : generatation of subkeys from a single key. Each round a slightly different key is used but that key is derived from original key.

A

Feistel Function (symmetric block cipher)

10
Q

modified structue where L0 and R0 are not equal lengths.

A

Unbalanced Feistel Cipher