Number theory

Question 1

combination

Answer 1

not concerned with the order

Question 2

permutation

Answer 2

all options considered including sequence

Question 3

Diffusion

Answer 3

• Changes to one character in the plain text affect multiple characters in the cipher text.
• ensures that any patterns in the plaintext, such as redundant bits, are not apparent in the ciphertext
• Achieved through transposition on P-boxes.

Question 4

Confusion

Answer 4

• Attempts to make the relationship between the statistical frequencies of the cipher text and the key as complex as possible.
• Substitution on S-boxes.

Question 5

Substitution

Answer 5

• Changing some part of the plain text for some matching part of cipher text.
• Historical algorithms typically use this.

Question 6

Two things all modern block cipher algorithms use

Answer 6

Substitution and Transposition

Question 7

How is the substitution portion of symmetric key cryptography accomplished?

Answer 7

• XORing the plain text message with the key,

* this obscures the relationship between the key and resulting ciphertext.

Question 8

How is transposition done in symmetric key cryptography?

Answer 8

Swapping blocks of text

Question 9

discrete

Answer 9

Finite qualitative data;

Probability, logic, integers

Question 10

continuous

Answer 10

Measured qualitative data;

Decimals, temperature
not used in standard cryptography

Question 11

P-box

Answer 11

• Shuffles the input bits around
• diffusion.
• transposed.

Question 12

S-box

Answer 12

• obscure the relationship between the key and the ciphertext.
• confusion.
• substitution.

Question 13

Traits of a good Pseudorandom Number Generator (PRNG)

Answer 13

Uncorrelated sequences and Long period