Chapter 6

Question 1

When developing a cryptographic system, what are the 3 different types of data:

Answer 1

At rest
Data in motion
Data in use - (active memory)

Question 2

Message Integrity is enforced through the use of encrypted message _____, known as ____ ____

Answer 2

Message Integrity is enforced through the use of encrypted message DIGESTS, known as DIGITAL SIGNATURES

Question 3

In authentication, name of the technique to ensure that Bob is who he claims to be

Answer 3

Challenge-response

Question 4

What is the key space?

Answer 4

Is the range of values that are valid for use as a key for a specific algorithm.
Set of all possible permutation for a key

Question 5

Bit size

Answer 5

Number of binary bits (0s and 1s) in the key

Question 6

Kerckhoffs principle

Answer 6

Concept about encryption to keep algorithms known and public

Question 7

Difference between cryptography and cryptanalysis

Answer 7

cryptography - art of creating secret codes and cipher

cryptanalyis - the study of methods to defeat codes and ciphers

Question 8

AND simbol:

Question 9

OR simbol:

Answer 9

v

Question 10

What is Exclusive OR (XOR)? When XOR is true?

Answer 10

It’s TRUE only when ONLY ONE of the input is true
0 x 1 = 1
1 x 0 = 1

0 x 0 FALSE
1 X 1 TRUE

Question 11

NONCE definition

Answer 11

randon number generated at the moment of processing for one-time use

Question 12

Zero Knowledge proof

Answer 12

Cryptography mechanism to prove your knowledge of a fact to a third party without the revealing the fact itself to that third party.

Question 13

WHen usually “zero knowledge proof” is usually applied?

Answer 13

Passwords and other secret authentications

Question 14

Split knowledge definition

Answer 14

WHen the information or privilege required to perform an operation is divided among multiple users.

Question 15

Work Function - Definition in cryptography

Answer 15

It’s a measure of the strenght. It’s how long a password takes to be brute-forced. The size of the work functions should be matched against the relative value of the protected asset.

Question 16

Difference among “code” and “cipher”

Answer 16

Code is a way to represent words or phrases, sometimes secret but they are NOT necessarily meant to provide CONFIDENTIALITY

Cipher is MEANT to PROVIDE CONFIDENTIALITY

Question 17

Transposition Ciphers, what does that do?

Answer 17

Rearrange the letters of a plaintext message

Question 18

Substitution Ciphers how does it work?

Answer 18

Replacing each character or bit of the plaintext message with a different character

Question 19

Polyalphabetic substitution ciphers how does it work

Answer 19

Provide multiple alphabets in the same message to hinder decryption efforts

Question 20

Polyalphabetic substitution protects against _____ _______ analysis, but it is vulnerable to a second-order form of frequency analysis called _______ analysis

Answer 20

Polyalphabetic substitution protects against DIRECT FREQUENCY analysis, but it is vulnerable to a second-order form of frequency analysis called PERIOD analysis

Question 21

HOw does One-Time Pads works?

Answer 21

it uses a different substitution alphabet for each letter of the plain text message.

Question 22

what are the 4 requirements to ensure the integrity of the One-TIme pad algorithm?

Answer 22

The pad must be randomly generated
it has to be 
Physically protected against disclosure
Must be used only once
Key at least as long as the message to be encrypted

Question 23

Running Key Ciphers definition

Answer 23

Also known as “Common book”. The encryption key is as long as the message itself and is often chosen from a common book`